Genitourinary ImagingFree Access

Immunoglobulin G4–related Disease of the Genitourinary System: Spectrum of Imaging Findings and Clinical-Pathologic Features

Published Online:https://doi.org/10.1148/rg.2020200043

Abstract

Immunoglobulin G4–related disease (IgG4-RD) is a systemic fibroinflammatory disease characterized by focal or diffuse organ infiltration of IgG4-bearing plasma cells. The diagnosis of IgG4-RD is based on a combination of clinical, serologic, radiologic, and histopathologic findings. IgG4-RD has been reported to affect almost all organ systems. The kidney is the most frequently involved of the genitourinary organs. The most common renal manifestation of IgG4-RD is IgG4-RD tubulointerstitial nephritis, followed by membranous glomerulonephropathy and, less frequently, obstructive nephropathy involving the renal pelvis, ureter, or retroperitoneum. Renal parenchymal lesions may appear as multiple nodular lesions, diffuse patchy infiltrative lesions, or a single nodular lesion. Multiple small nodular cortical lesions are the most common imaging findings of IgG4-RD involving the kidney. Renal pelvic, sinus, or perinephric lesions can also occur. IgG4-RD involvement of other genitourinary organs including the ureter, bladder, urethra, and male and female reproductive organs is rare compared with kidney involvement but may show variable imaging findings such as a localized mass within or surrounding the involved organ or diffuse enlargement of the involved organ. Imaging findings of IgG4-RD involving the genitourinary system are nonspecific but should be differentiated from inflammatory and neoplastic lesions that mimic IgG4-RD.

The online slide presentation from the RSNA Annual Meeting is available for this article.

©RSNA, 2020

SA-CME LEARNING OBJECTIVES

After completing this journal-based SA-CME activity, participants will be able to:

  • ■ Recognize the clinical-pathologic features of IgG4-RD involving the genitourinary system.

  • ■ Describe the variable imaging findings of IgG4-RD involving the genitourinary system.

  • ■ Discuss the differential diagnosis for each affected organ.

Introduction

Immunoglobulin G4-related disease (IgG4-RD) is a systemic autoimmune disease characterized by sclerotic tumefactive lesions that contain dense lymphoplasmacytic infiltrates that are rich in IgG4-positive plasma cells, obliterative phlebitis, storiform fibrosis, and, often but not always, elevated serum IgG4 concentrations (1). Although IgG4-RD was initially reported in the pancreas, it is now well known as a systemic disease that can affect multiple body sites. Historically, the concept of autoimmune pancreatitis was proposed by Yoshida et al (2) in 1995, and Kamisawa et al (3) suggested that IgG4-RD is a systemic disease in 2003, when extrapancreatic manifestations were identified in patients with autoimmune pancreatitis. Since then, IgG4-RD has been reported in virtually every organ system (not just the pancreas) including the biliary tree, lacrimal glands, salivary glands, periorbital tissues, thyroid gland, kidneys, retroperitoneum, mesentery, lungs, lymph nodes, meninges, aorta, breasts, prostate, gastrointestinal tract, pericardium, and skin (1,4) (Table 1). The prevalence of various organ manifestations remains unclear, but type 1 autoimmune pancreatitis, IgG4-RD cholangitis, sialadenitis, dacryoadenitis, and retroperitoneal fibrosis are the most common disease features (5). IgG4-RD can also affect the genitourinary system including the kidneys, ureter, urinary bladder, urethra, prostate gland, testes, and female reproductive organs (6).

Table 1: Representative Body Sites Affected by IgG4-RD

Table 1:

The diagnosis of IgG4-RD is usually based on a combination of clinical, radiologic, and serologic findings with the characteristic histopathologic features. The accurate and timely diagnosis of IgG4-RD is vital to prevent irreversible fibrosis and organ dysfunction, because IgG4-RD is medically treatable with steroids or other secondary immunosuppressants. IgG4-RD typically manifests as a mass or an enlargement of affected organs that mimics a malignancy or inflammation (5). As in other organ involvement, IgG4-RD that affects the genitourinary system can mimic malignant disease and benign inflammatory disease, showing similar clinical symptoms and radiologic findings. The diagnosis of IgG4-RD can be more difficult when less frequently affected organs are involved, and a high index of clinical suspicion is required to avoid unnecessary surgery (7).

In this article, we first provide a general overview of IgG4-RD and then focus on a review of IgG4-RD of the genitourinary system, including the kidneys, ureter, bladder, urethra, and male and female reproductive organs, and show various imaging manifestations of these diseases. We also describe the differential diagnosis of and conditions that mimic IgG4-RD of the genitourinary system.

Overview of IgG4-RD

Epidemiology

Although IgG4-RD has been recognized and reported worldwide, the incidence and prevalence remain poorly described, because it was recognized as a discrete disease relatively recently. The disease is prevalent in middle-aged men, with an average age of onset of 50–70 years and a male-to-female ratio ranging from 5:1 to 1.6:1 (8).

Pathophysiology

The pathogenesis of IgG4-RD remains largely unclear and the exact role of the IgG molecule has not been identified. Previous research (7) revealed that the inflammatory and fibrotic processes that drive IgG4-RD are initiated by a combination of T-helper type 2 cells and regulatory T cells. The inflammatory process contributes to the eosinophilia, elevated serum IgG4 and immunoglobulin E concentrations, and progression of fibrosis that are characteristic of IgG4-RD. Massive infiltration of inflammatory cells leads to tumefactive enlargement of the involved organs and organ dysfunction (9). Still, further evaluation of the immune-mediated pathway of IgG4-RD is necessary to generate potential targets that can result in the elimination of IgG4-mediated inflammation and fibrosis (7).

Clinical Manifestations

The clinical manifestations of IgG4-RD are widely variable and can occur in more than one organ synchronously or metachronously over months to years. IgG4-RD can involve almost all organ systems but has strong predilections for the pancreas, biliary tree, salivary glands, orbits, lacrimal glands, lungs, kidneys, aorta, retroperitoneum, meninges, and thyroid gland (10). The kidneys are the most common of the genitourinary system organs to be involved in IgG4-RD. Involvement of other genitourinary organs such as the ureter, bladder, and prostate is rare (6). Most patients with IgG4-RD show subacute or chronic symptoms at clinical presentation, and the representative clinical manifestations are site-specific and originate from the mass effect of involved organs. Manifestations of IgG4-RD broadly range from mild localized symptoms to major tissue damage and subsequent organ failure (7). IgG4-RD is often diagnosed incidentally through radiologic findings or unexpectedly in pathologic specimens. Constitutional symptoms such as fever, malaise, and weight loss are rarely seen but can occur due to the systemic inflammatory response of IgG4-RD (11).

Diagnosis

Diagnosis of IgG4-RD is based on a combination of clinical, serologic, radiologic, and histopathologic findings (5). None of these findings alone provide definitive evidence for the diagnosis. Cross-sectional imaging (ie, US, CT, and MRI) is an important part of the diagnostic approach and management of IgG4-RD. In patients with hydronephrosis and impaired renal function, retrograde pyelography may be performed to evaluate the ureters and collecting systems of the kidneys (12). However, the imaging findings are generally nonspecific and may be variable, particularly in the kidneys and lungs, and do not reliably show distinctions between IgG4-RD and its mimics. The exception to the rule is when the imaging findings are in the pancreas.

The characteristic imaging findings of autoimmune pancreatitis, which include sausage-like enlargement of the pancreas and a peripancreatic halo, can be strongly suggestive of IgG4-RD if they are detected in the proper clinical context that includes (a) mild abdominal symptoms, usually without acute attacks of pancreatitis; (b) occasional occurrence of obstructive jaundice; (c) increased serum gamma globulin, IgG, and/or IgG4 concentrations; and (d) occasional association with other organ involvement (13). The presence of a peripancreatic halo corresponding to a fibroinflammatory process extending into the peripancreatic adipose tissue is a useful imaging finding for the diagnosis of IgG4-RD and for differentiating it from pancreatic cancer or other pancreatitis (14).

Fluorine 18 (18F)-fluorodeoxyglucose (FDG) PET/CT is mainly used to determine the extent of organ involvement of IgG4-RD for whole-body screening and to monitor disease activity after treatment (15,16). In a subset of patients with classic combinations of clinical, serologic, or radiologic findings, clinical diagnoses are sometimes made in the absence of biopsy (17). Nevertheless, tissue biopsy is the standard for diagnosis in most settings, especially in patients without pancreatic involvement, because differentiation of IgG4-RD from malignant tumors is crucial. The three key histopathologic findings for diagnosis of IgG4-RD are dense lymphoplasmacytic infiltration with increased IgG4-positive plasma cells, obliterative phlebitis, and storiform fibrosis (18) (Fig 1).

Histopathologic features of IgG4-RD of the kidney in a 68-year-old                         man. (a) Photomicrograph shows dense lymphoplasmacytic infiltration (arrows)                         with storiform fibrosis (arrowheads). (Hematoxylin-eosin stain; original                         magnification, ×400.) (b) Photomicrograph shows obliterative phlebitis                         (arrowheads). (Periodic acid-Schiff stain; original magnification,                         ×400.) (c) Photomicrographs show numerous brown IgG- and IgG4-positive                         plasma cells (arrows) with an increased ratio of IgG4 to IgG cells. (Left,                         IgG immunostain; right, IgG4 immunostain; original magnification,                         ×400.)

Figure 1a. Histopathologic features of IgG4-RD of the kidney in a 68-year-old man. (a) Photomicrograph shows dense lymphoplasmacytic infiltration (arrows) with storiform fibrosis (arrowheads). (Hematoxylin-eosin stain; original magnification, ×400.) (b) Photomicrograph shows obliterative phlebitis (arrowheads). (Periodic acid-Schiff stain; original magnification, ×400.) (c) Photomicrographs show numerous brown IgG- and IgG4-positive plasma cells (arrows) with an increased ratio of IgG4 to IgG cells. (Left, IgG immunostain; right, IgG4 immunostain; original magnification, ×400.)

Histopathologic features of IgG4-RD of the kidney in a 68-year-old                         man. (a) Photomicrograph shows dense lymphoplasmacytic infiltration (arrows)                         with storiform fibrosis (arrowheads). (Hematoxylin-eosin stain; original                         magnification, ×400.) (b) Photomicrograph shows obliterative phlebitis                         (arrowheads). (Periodic acid-Schiff stain; original magnification,                         ×400.) (c) Photomicrographs show numerous brown IgG- and IgG4-positive                         plasma cells (arrows) with an increased ratio of IgG4 to IgG cells. (Left,                         IgG immunostain; right, IgG4 immunostain; original magnification,                         ×400.)

Figure 1b. Histopathologic features of IgG4-RD of the kidney in a 68-year-old man. (a) Photomicrograph shows dense lymphoplasmacytic infiltration (arrows) with storiform fibrosis (arrowheads). (Hematoxylin-eosin stain; original magnification, ×400.) (b) Photomicrograph shows obliterative phlebitis (arrowheads). (Periodic acid-Schiff stain; original magnification, ×400.) (c) Photomicrographs show numerous brown IgG- and IgG4-positive plasma cells (arrows) with an increased ratio of IgG4 to IgG cells. (Left, IgG immunostain; right, IgG4 immunostain; original magnification, ×400.)

Histopathologic features of IgG4-RD of the kidney in a 68-year-old                         man. (a) Photomicrograph shows dense lymphoplasmacytic infiltration (arrows)                         with storiform fibrosis (arrowheads). (Hematoxylin-eosin stain; original                         magnification, ×400.) (b) Photomicrograph shows obliterative phlebitis                         (arrowheads). (Periodic acid-Schiff stain; original magnification,                         ×400.) (c) Photomicrographs show numerous brown IgG- and IgG4-positive                         plasma cells (arrows) with an increased ratio of IgG4 to IgG cells. (Left,                         IgG immunostain; right, IgG4 immunostain; original magnification,                         ×400.)

Figure 1c. Histopathologic features of IgG4-RD of the kidney in a 68-year-old man. (a) Photomicrograph shows dense lymphoplasmacytic infiltration (arrows) with storiform fibrosis (arrowheads). (Hematoxylin-eosin stain; original magnification, ×400.) (b) Photomicrograph shows obliterative phlebitis (arrowheads). (Periodic acid-Schiff stain; original magnification, ×400.) (c) Photomicrographs show numerous brown IgG- and IgG4-positive plasma cells (arrows) with an increased ratio of IgG4 to IgG cells. (Left, IgG immunostain; right, IgG4 immunostain; original magnification, ×400.)

A confident pathologic diagnosis of IgG4-RD usually requires the presence of two of the three major histologic features. In most cases, the two features are dense lymphoplasmacytic infiltrate and storiform fibrosis. Additional histologic findings including a moderate amount of tissue eosinophilia, dense infiltrates of IgG4-positive plasma cells (>10 per high-power field of the biopsy sample), and a ratio of IgG4-positive to IgG-positive plasma cells of higher than 40% are also useful in certain cases (18).

Serologic Evaluation

A high serum IgG4 level is neither sufficiently sensitive nor specific for diagnosis (5). A high serum IgG4 concentration is commonly seen in patients with IgG4-RD, but the serum IgG4 level may be normal in 20%–40% of patients with biopsy-proven IgG4-RD. Monitoring of serum IgG4 concentrations seems useful in assessment of disease activity in some patients, but this measurement should never be used as the sole determinant in treatment decisions. The serum IgG4 concentration declines substantially after glucocorticoid treatment in most patients, but a multicenter study (19) from Japan showed that IgG4 levels did not return to the normal range in 115 of 182 (63%) patients treated with glucocorticoids. Clinical relapses occurred in 10% of patients who showed persistently normal IgG4 concentrations (19). Therefore, serum IgG4 is closely related to IgG4-RD but is not pathognomonic, which emphasizes the importance of radiologic findings of affected organs, pathologic correlation, and treatment response to steroids for the diagnosis of IgG4-RD.

Treatment

Glucocorticoids are effective and rapid as the first-line treatment for IgG4-RD (5). However, recurrence occurs frequently. For relapse prevention, long-term corticosteroid maintenance might be required for up to several years. A rapid response to glucocorticoids provides additional diagnostic confirmation if a tissue diagnosis was not performed before the start of treatment. Radiologic improvement appears 1–2 weeks after steroid therapy is started (19,20). A poor response to glucocorticoids should raise the possibility of other diagnoses, especially cancer, although the response to glucocorticoids varies according to the affected organs and the degree of fibrosis (5). Immunosuppressants such as methotrexate, azathioprine, or mycophenolate mofetil can be alternative therapeutic options when IgG4-RD is refractory to glucocorticoid therapy (21).

IgG4-RD of the Genitourinary System

IgG4-RD of the Kidney

Teaching Point The kidneys are the genitourinary organs most commonly involved with IgG4-RD (6). Kidney involvement is found in approximately one-fourth to one-third of patients with IgG4-RD autoimmune pancreatitis but can also occur without the involvement of other organs (22,23).
The term IgG4-RD of the kidney refers to any pattern of renal involvement in IgG4-RD (24).
Teaching Point IgG4-RD of the kidney predominantly involves the renal cortex, but the renal pelvis, renal sinus, and perirenal space can be involved. The most frequent renal manifestation of IgG4-RD is IgG4-RD tubulointerstitial nephritis, followed by IgG4-RD membranous glomerulonephropathy. Less frequently, obstructive nephropathy can be caused by postrenal obstruction secondary to renal pelvis, ureter, or retroperitoneal involvement (25,26).

Patients with IgG4-RD of the kidney present at an average age of 65 years (range, 14–85 years) with a male-to-female ratio of 4:1 to 3:1, which is similar to that in patients with IgG4-RD involving other organs (16,22,24,27). Patients with IgG4-RD of the kidney usually present with mild symptoms or are asymptomatic. The usual symptoms include hematuria and an elevated serum creatinine level caused by acute renal injury, obstructive uropathy, and flank pain similar to that with renal malignancy. However, two well-recognized major clinical manifestations are incidental abnormal imaging findings during systemic screening workup for IgG4-RD and unexplained renal dysfunction (16). Approximately 80% of patients with IgG4-RD of the kidney show elevation of serum IgG4 levels (22).

Imaging Spectrum of IgG4-RD of the Kidney

IgG4-RD of the kidney may show a broad spectrum of imaging manifestations according to the involved anatomic location and stage of disease. Because the imaging findings of IgG4-RD of the kidney are diverse and nonspecific, radiologists should be familiar with them when considering IgG4-RD in the differential diagnosis. According to its location, IgG4-RD of the kidney can be divided into renal parenchymal lesions, renal pelvic and/or sinus lesions, and perinephric lesions (23). Of these, renal parenchymal lesions are the most common manifestation of IgG4-RD of the kidney.

IgG4-RD of the Kidney Involving the Renal Parenchyma.

Teaching Point Renal parenchymal IgG4-RD may show several imaging patterns, including multiple nodular lesions, diffuse patchy infiltrative lesions, and a single nodular lesion. Of these, the multiple nodular type is the most common imaging finding for IgG4-RD of the kidney (22,23,28).
At CT or MRI, multiple nodules demonstrate well-defined or ill-defined round or wedge-shaped relatively uniform and small (<15 mm in diameter) lesions located in the renal cortex (Fig 2). Cortical nodules show homogeneous hypoattenuation at contrast-enhanced CT, representing a fibroinflammatory component. There tend to be few nodules, and bilateral involvement of the kidneys is common. The small peripheral cortical nodules may be a specific finding of IgG4-RD of the kidney (22). Lesions are isointense at T1-weighted MRI and hypointense at T2-weighted MRI (Fig 3). At dynamic contrast-enhanced MRI, lesions show gradual progressive enhancement (22,23,29). Renal lesions may show diffusion restriction at diffusion-weighted MRI. Kim et al (29) reported higher sensitivity at diffusion-weighted MRI than that at T2-weighted MRI for the detection of IgG4-RD of the kidney. MRI findings may reflect increased cellularity and fibrosis of IgG4-RD of the kidney. Diffusion-weighted MRI can be promising in a patient with impaired renal function.

Multiple nodular IgG4-RD of the kidney in a 78-year-old woman with a                         chilling sensation. Her serum IgG4 level was 69.2 mg/dL (0.692 g/L), with a                         reference range of 3.9–86.4 (0.039–0.864 g/L). Axial                         contrast-enhanced nephrographic phase CT image shows several well-defined                         round hypoattenuating nodules (arrows) in both kidneys. US-guided biopsy of                         the kidney allowed confirmation of the diagnosis of IgG4-RD of the                         kidney.

Figure 2. Multiple nodular IgG4-RD of the kidney in a 78-year-old woman with a chilling sensation. Her serum IgG4 level was 69.2 mg/dL (0.692 g/L), with a reference range of 3.9–86.4 (0.039–0.864 g/L). Axial contrast-enhanced nephrographic phase CT image shows several well-defined round hypoattenuating nodules (arrows) in both kidneys. US-guided biopsy of the kidney allowed confirmation of the diagnosis of IgG4-RD of the kidney.

Multiple nodular IgG4-RD of the kidney in a 57-year-old man with a                         febrile sensation for 3 months and impaired renal function. His serum IgG4                         level was 13 200 mg/dL (132 g/L) with a reference range of                         3–201 mg/dL (0.03–2.01 g/L). Axial T2-weighted MR image shows                         several small hypointense nodular lesions (arrows) in both kidneys.                         US-guided biopsy of the kidney allowed confirmation of IgG4-RD of the                         kidney.

Figure 3. Multiple nodular IgG4-RD of the kidney in a 57-year-old man with a febrile sensation for 3 months and impaired renal function. His serum IgG4 level was 13 200 mg/dL (132 g/L) with a reference range of 3–201 mg/dL (0.03–2.01 g/L). Axial T2-weighted MR image shows several small hypointense nodular lesions (arrows) in both kidneys. US-guided biopsy of the kidney allowed confirmation of IgG4-RD of the kidney.

The diffuse patchy infiltrative type of IgG4-RD of the kidney is a less-common imaging manifestation than that of multiple nodular lesions of the renal cortex. At CT, patchy or confluent lesions on the base of the renal capsule show hypoattenuation relative to the normal renal parenchyma (Fig 4). Diffuse patchy lesions are more likely larger than cortical nodular lesions and probably represent a more progressed stage of IgG4-RD of the kidney (22). Diffuse bilateral renal enlargement is seen in approximately 20% of patients with IgG4-RD tubulointerstitial nephritis (30).

Diffuse patchy infiltrative IgG4-RD of the kidney in a 64-year-old man                         with incidental abnormal CT findings during a health screening workup. (a)                         Axial contrast-enhanced CT image shows multiple ill-defined patchy or                         confluent hypoattenuating lesions (arrows) in both kidneys. His serum                         creatinine level was normal, and his serum IgG4 level was not checked.                         Multiple mildly enlarged lymph nodes were seen in the retroperitoneum (not                         shown). US-guided biopsy of the kidney confirmed IgG4-RD of the kidney. (b)                         Contrast-enhanced CT image obtained after completion of steroid treatment                         shows improvement in the bilateral renal parenchymal lesions. However,                         multifocal tiny cortical scars remain (arrowheads). The retroperitoneal                         lymph nodes were smaller after steroid treatment (not shown).

Figure 4a. Diffuse patchy infiltrative IgG4-RD of the kidney in a 64-year-old man with incidental abnormal CT findings during a health screening workup. (a) Axial contrast-enhanced CT image shows multiple ill-defined patchy or confluent hypoattenuating lesions (arrows) in both kidneys. His serum creatinine level was normal, and his serum IgG4 level was not checked. Multiple mildly enlarged lymph nodes were seen in the retroperitoneum (not shown). US-guided biopsy of the kidney confirmed IgG4-RD of the kidney. (b) Contrast-enhanced CT image obtained after completion of steroid treatment shows improvement in the bilateral renal parenchymal lesions. However, multifocal tiny cortical scars remain (arrowheads). The retroperitoneal lymph nodes were smaller after steroid treatment (not shown).

Diffuse patchy infiltrative IgG4-RD of the kidney in a 64-year-old man                         with incidental abnormal CT findings during a health screening workup. (a)                         Axial contrast-enhanced CT image shows multiple ill-defined patchy or                         confluent hypoattenuating lesions (arrows) in both kidneys. His serum                         creatinine level was normal, and his serum IgG4 level was not checked.                         Multiple mildly enlarged lymph nodes were seen in the retroperitoneum (not                         shown). US-guided biopsy of the kidney confirmed IgG4-RD of the kidney. (b)                         Contrast-enhanced CT image obtained after completion of steroid treatment                         shows improvement in the bilateral renal parenchymal lesions. However,                         multifocal tiny cortical scars remain (arrowheads). The retroperitoneal                         lymph nodes were smaller after steroid treatment (not shown).

Figure 4b. Diffuse patchy infiltrative IgG4-RD of the kidney in a 64-year-old man with incidental abnormal CT findings during a health screening workup. (a) Axial contrast-enhanced CT image shows multiple ill-defined patchy or confluent hypoattenuating lesions (arrows) in both kidneys. His serum creatinine level was normal, and his serum IgG4 level was not checked. Multiple mildly enlarged lymph nodes were seen in the retroperitoneum (not shown). US-guided biopsy of the kidney confirmed IgG4-RD of the kidney. (b) Contrast-enhanced CT image obtained after completion of steroid treatment shows improvement in the bilateral renal parenchymal lesions. However, multifocal tiny cortical scars remain (arrowheads). The retroperitoneal lymph nodes were smaller after steroid treatment (not shown).

Although rare, IgG4-RD of the kidney involving the renal parenchyma can manifest as a single nodular lesion (Fig 5). At CT and MRI, the single nodular lesion is peripherally located in the renal cortex and is smaller, with an ill-defined margin in the early stage of renal involvement (22).

Single nodular IgG4-RD of the kidney in a 58-year-old man with left                         flank discomfort. His serum IgG4 level was 222.3 mg/dL (2.22 g/L) with a                         reference range of 3.9–86.4 mg/dL (0.039–0.86 g/L). (a) Axial                         contrast-enhanced CT image shows a 1.7-cm round hypoattenuating nodular                         lesion (arrow) in the left kidney. The round lesion in the right kidney                         (arrowhead) is a parapelvic cyst. (b) Axial fat-suppressed T2-weighted MR                         image shows a hypointense nodular lesion with peripheral high signal                         intensity (arrow) in the left kidney. (c) Axial diffusion-weighted MR image                         (b = 1000 sec/mm2) (left) and apparent diffusion coefficient map                         (right) show a single nodular lesion (arrow) that appears hyperintense and                         hypointense, respectively, and represents diffusion restriction. US-guided                         biopsy of the kidney allowed confirmation of IgG4-RD of the kidney. ADC                         = apparent diffusion coefficient.

Figure 5a. Single nodular IgG4-RD of the kidney in a 58-year-old man with left flank discomfort. His serum IgG4 level was 222.3 mg/dL (2.22 g/L) with a reference range of 3.9–86.4 mg/dL (0.039–0.86 g/L). (a) Axial contrast-enhanced CT image shows a 1.7-cm round hypoattenuating nodular lesion (arrow) in the left kidney. The round lesion in the right kidney (arrowhead) is a parapelvic cyst. (b) Axial fat-suppressed T2-weighted MR image shows a hypointense nodular lesion with peripheral high signal intensity (arrow) in the left kidney. (c) Axial diffusion-weighted MR image (b = 1000 sec/mm2) (left) and apparent diffusion coefficient map (right) show a single nodular lesion (arrow) that appears hyperintense and hypointense, respectively, and represents diffusion restriction. US-guided biopsy of the kidney allowed confirmation of IgG4-RD of the kidney. ADC = apparent diffusion coefficient.

Single nodular IgG4-RD of the kidney in a 58-year-old man with left                         flank discomfort. His serum IgG4 level was 222.3 mg/dL (2.22 g/L) with a                         reference range of 3.9–86.4 mg/dL (0.039–0.86 g/L). (a) Axial                         contrast-enhanced CT image shows a 1.7-cm round hypoattenuating nodular                         lesion (arrow) in the left kidney. The round lesion in the right kidney                         (arrowhead) is a parapelvic cyst. (b) Axial fat-suppressed T2-weighted MR                         image shows a hypointense nodular lesion with peripheral high signal                         intensity (arrow) in the left kidney. (c) Axial diffusion-weighted MR image                         (b = 1000 sec/mm2) (left) and apparent diffusion coefficient map                         (right) show a single nodular lesion (arrow) that appears hyperintense and                         hypointense, respectively, and represents diffusion restriction. US-guided                         biopsy of the kidney allowed confirmation of IgG4-RD of the kidney. ADC                         = apparent diffusion coefficient.

Figure 5b. Single nodular IgG4-RD of the kidney in a 58-year-old man with left flank discomfort. His serum IgG4 level was 222.3 mg/dL (2.22 g/L) with a reference range of 3.9–86.4 mg/dL (0.039–0.86 g/L). (a) Axial contrast-enhanced CT image shows a 1.7-cm round hypoattenuating nodular lesion (arrow) in the left kidney. The round lesion in the right kidney (arrowhead) is a parapelvic cyst. (b) Axial fat-suppressed T2-weighted MR image shows a hypointense nodular lesion with peripheral high signal intensity (arrow) in the left kidney. (c) Axial diffusion-weighted MR image (b = 1000 sec/mm2) (left) and apparent diffusion coefficient map (right) show a single nodular lesion (arrow) that appears hyperintense and hypointense, respectively, and represents diffusion restriction. US-guided biopsy of the kidney allowed confirmation of IgG4-RD of the kidney. ADC = apparent diffusion coefficient.

Single nodular IgG4-RD of the kidney in a 58-year-old man with left                         flank discomfort. His serum IgG4 level was 222.3 mg/dL (2.22 g/L) with a                         reference range of 3.9–86.4 mg/dL (0.039–0.86 g/L). (a) Axial                         contrast-enhanced CT image shows a 1.7-cm round hypoattenuating nodular                         lesion (arrow) in the left kidney. The round lesion in the right kidney                         (arrowhead) is a parapelvic cyst. (b) Axial fat-suppressed T2-weighted MR                         image shows a hypointense nodular lesion with peripheral high signal                         intensity (arrow) in the left kidney. (c) Axial diffusion-weighted MR image                         (b = 1000 sec/mm2) (left) and apparent diffusion coefficient map                         (right) show a single nodular lesion (arrow) that appears hyperintense and                         hypointense, respectively, and represents diffusion restriction. US-guided                         biopsy of the kidney allowed confirmation of IgG4-RD of the kidney. ADC                         = apparent diffusion coefficient.

Figure 5c. Single nodular IgG4-RD of the kidney in a 58-year-old man with left flank discomfort. His serum IgG4 level was 222.3 mg/dL (2.22 g/L) with a reference range of 3.9–86.4 mg/dL (0.039–0.86 g/L). (a) Axial contrast-enhanced CT image shows a 1.7-cm round hypoattenuating nodular lesion (arrow) in the left kidney. The round lesion in the right kidney (arrowhead) is a parapelvic cyst. (b) Axial fat-suppressed T2-weighted MR image shows a hypointense nodular lesion with peripheral high signal intensity (arrow) in the left kidney. (c) Axial diffusion-weighted MR image (b = 1000 sec/mm2) (left) and apparent diffusion coefficient map (right) show a single nodular lesion (arrow) that appears hyperintense and hypointense, respectively, and represents diffusion restriction. US-guided biopsy of the kidney allowed confirmation of IgG4-RD of the kidney. ADC = apparent diffusion coefficient.

IgG4-RD of the Kidney Involving the Renal Pelvis or Sinus and the Perinephric Space.—Renal pelvis or sinus or perinephric lesions are far less common than renal parenchymal lesions. IgG4-RD of the kidney involving the renal pelvis or renal sinus may show diffuse wall thickening of the renal pelvis, with a smooth intraluminal surface or a soft-tissue nodule in the renal sinus (22,23,28) (Fig 6). Renal pelvis and/or sinus involvement can be either unilateral or bilateral (Fig 7). In some cases, renal parenchymal, pelvic or sinus, or perinephric involvement occur synchronously (Fig 8). Perinephric involvement of IgG4-RD of the kidney manifests as a unilateral or bilateral soft-tissue–attenuation rim surrounding the kidneys, with or without renal cortical involvement (Fig 9).

Unilateral renal pelvis or sinus lesion of IgG4-RD of the kidney in a                         68-year-old man with right flank discomfort. Contrast-enhanced excretory                         phase CT image shows an ill-defined mildly enhancing                         soft-tissue–attenuation lesion (arrow) encasing the right renal                         pelvis or sinus and without hydronephrosis. Right nephroureterectomy was                         performed for suspicion of urothelial cell carcinoma. Histopathologic                         examination (see Fig 1) revealed IgG4-RD of the kidney involving the                         ureteropelvic junction.

Figure 6. Unilateral renal pelvis or sinus lesion of IgG4-RD of the kidney in a 68-year-old man with right flank discomfort. Contrast-enhanced excretory phase CT image shows an ill-defined mildly enhancing soft-tissue–attenuation lesion (arrow) encasing the right renal pelvis or sinus and without hydronephrosis. Right nephroureterectomy was performed for suspicion of urothelial cell carcinoma. Histopathologic examination (see Fig 1) revealed IgG4-RD of the kidney involving the ureteropelvic junction.

Bilateral renal pelvic or sinus lesions in a 48-year-old man with                         IgG4-RD of the kidney and an incidental abnormal CT finding during follow-up                         for liver cirrhosis. Coronal contrast-enhanced corticomedullary phase CT                         image shows ill-defined mildly enhancing soft-tissue infiltrative lesions                         (arrows) encasing the bilateral renal pelvis or sinus, without                         hydronephrosis. A combination of diffuse pancreatic enlargement (not shown)                         and bilateral renal pelvic or sinus lesions at CT strongly suggests IgG4-RD.                         After steroid treatment, bilateral renal pelvic or sinus lesions and                         pancreatic enlargement regressed (not shown).

Figure 7. Bilateral renal pelvic or sinus lesions in a 48-year-old man with IgG4-RD of the kidney and an incidental abnormal CT finding during follow-up for liver cirrhosis. Coronal contrast-enhanced corticomedullary phase CT image shows ill-defined mildly enhancing soft-tissue infiltrative lesions (arrows) encasing the bilateral renal pelvis or sinus, without hydronephrosis. A combination of diffuse pancreatic enlargement (not shown) and bilateral renal pelvic or sinus lesions at CT strongly suggests IgG4-RD. After steroid treatment, bilateral renal pelvic or sinus lesions and pancreatic enlargement regressed (not shown).

Synchronous renal parenchymal and pelvic or sinus involvement of                         IgG4-RD of the kidney in a 36-year-old woman with an incidental abnormal CT                         finding during a health screening workup. Her serum IgG4 level was 4160                         mg/dL (41.60 g/L), with a reference range of 3–201 mg/dL                         (0.03–2.01 g/L). (a) Coronal contrast-enhanced nephrographic phase CT                         image shows several well-defined round hypoattenuating nodular lesions in                         the bilateral renal cortex (arrows) and soft-tissue infiltration in the left                         renal pelvis or sinus (arrowhead). US-guided biopsy of the kidney allowed                         confirmation of IgG4-RD of the kidney. (b) Coronal contrast-enhanced CT                         image acquired after completion of steroid treatment shows regression of                         bilateral renal parenchymal and left pelvic or sinus lesions.

Figure 8a. Synchronous renal parenchymal and pelvic or sinus involvement of IgG4-RD of the kidney in a 36-year-old woman with an incidental abnormal CT finding during a health screening workup. Her serum IgG4 level was 4160 mg/dL (41.60 g/L), with a reference range of 3–201 mg/dL (0.03–2.01 g/L). (a) Coronal contrast-enhanced nephrographic phase CT image shows several well-defined round hypoattenuating nodular lesions in the bilateral renal cortex (arrows) and soft-tissue infiltration in the left renal pelvis or sinus (arrowhead). US-guided biopsy of the kidney allowed confirmation of IgG4-RD of the kidney. (b) Coronal contrast-enhanced CT image acquired after completion of steroid treatment shows regression of bilateral renal parenchymal and left pelvic or sinus lesions.

Synchronous renal parenchymal and pelvic or sinus involvement of                         IgG4-RD of the kidney in a 36-year-old woman with an incidental abnormal CT                         finding during a health screening workup. Her serum IgG4 level was 4160                         mg/dL (41.60 g/L), with a reference range of 3–201 mg/dL                         (0.03–2.01 g/L). (a) Coronal contrast-enhanced nephrographic phase CT                         image shows several well-defined round hypoattenuating nodular lesions in                         the bilateral renal cortex (arrows) and soft-tissue infiltration in the left                         renal pelvis or sinus (arrowhead). US-guided biopsy of the kidney allowed                         confirmation of IgG4-RD of the kidney. (b) Coronal contrast-enhanced CT                         image acquired after completion of steroid treatment shows regression of                         bilateral renal parenchymal and left pelvic or sinus lesions.

Figure 8b. Synchronous renal parenchymal and pelvic or sinus involvement of IgG4-RD of the kidney in a 36-year-old woman with an incidental abnormal CT finding during a health screening workup. Her serum IgG4 level was 4160 mg/dL (41.60 g/L), with a reference range of 3–201 mg/dL (0.03–2.01 g/L). (a) Coronal contrast-enhanced nephrographic phase CT image shows several well-defined round hypoattenuating nodular lesions in the bilateral renal cortex (arrows) and soft-tissue infiltration in the left renal pelvis or sinus (arrowhead). US-guided biopsy of the kidney allowed confirmation of IgG4-RD of the kidney. (b) Coronal contrast-enhanced CT image acquired after completion of steroid treatment shows regression of bilateral renal parenchymal and left pelvic or sinus lesions.

Bilateral perinephric and renal sinus lesions of IgG4-RD of the kidney                         in an 80-year-old man with an incidental abnormal CT finding.                         Contrast-enhanced CT image shows a homogeneous rimlike soft-tissue mass                         surrounding the bilateral kidneys (arrows) and the renal sinus (arrowheads).                         The right kidney is atrophied due to chronic pyelonephritis. US-guided                         biopsy results confirmed IgG4-RD of the kidney.

Figure 9. Bilateral perinephric and renal sinus lesions of IgG4-RD of the kidney in an 80-year-old man with an incidental abnormal CT finding. Contrast-enhanced CT image shows a homogeneous rimlike soft-tissue mass surrounding the bilateral kidneys (arrows) and the renal sinus (arrowheads). The right kidney is atrophied due to chronic pyelonephritis. US-guided biopsy results confirmed IgG4-RD of the kidney.

Mimics of IgG4-RD of the Kidney.—As described previously, IgG4-RD of the kidney may show variable imaging manifestations and should be differentiated from diverse neoplastic or nonneoplastic disease entities that can mimic IgG4-RD of the kidney at imaging. Among them, renal lymphoma is one of the most important conditions in the differential diagnosis of IgG4-RD of the kidney. Renal lymphoma also has a wide spectrum of imaging manifestations, including multiple lesions, a solitary lesion, preferential perinephric space involvement, direct extension from large retroperitoneal masses, and diffuse renal enlargement of one or both kidneys (31). There is a substantial overlap of imaging findings between renal lymphoma and IgG4-RD of the kidneys. The most common imaging finding of renal lymphoma is multiple nodular parenchymal masses of variable size, which can be quite similar to those of multiple nodular IgG4-RD of the kidneys. However, renal lymphomas frequently accompany multiple retroperitoneal lymphadenopathy and show larger renal masses than does IgG4-RD of the kidneys (Figs 10, 11) (23). In rare cases, renal leukemia, multiple synchronous renal cell carcinomas, or multiple renal metastasis from lung cancer, breast cancer, gastric cancer, or melanoma may show multiple small renal parenchymal nodules (3133).

Multiple nodular renal lymphoma mimicking IgG4-RD of the kidney in a                         64-year-old man with poor oral intake and a palpable neck mass. Axial                         contrast-enhanced CT image shows several small hypoattenuating nodular                         lesions (arrows) in the right kidney and multiple enlarged retroperitoneal                         lymph nodes (arrowheads). There was splenomegaly (not shown). The imaging                         findings favored a diagnosis of lymphoma over IgG4-RD.

Figure 10. Multiple nodular renal lymphoma mimicking IgG4-RD of the kidney in a 64-year-old man with poor oral intake and a palpable neck mass. Axial contrast-enhanced CT image shows several small hypoattenuating nodular lesions (arrows) in the right kidney and multiple enlarged retroperitoneal lymph nodes (arrowheads). There was splenomegaly (not shown). The imaging findings favored a diagnosis of lymphoma over IgG4-RD.

Multiple nodular renal lymphoma in a 24-year-old woman with a palpable                         neck mass. Axial contrast-enhanced CT image shows bilateral renal                         enlargement and multiple variably sized hypoattenuating round mass-forming                         lesions (arrows) in both kidneys. Renal lymphomas frequently show larger                         renal masses with mass effect than those of IgG4-RD of the                         kidney.

Figure 11. Multiple nodular renal lymphoma in a 24-year-old woman with a palpable neck mass. Axial contrast-enhanced CT image shows bilateral renal enlargement and multiple variably sized hypoattenuating round mass-forming lesions (arrows) in both kidneys. Renal lymphomas frequently show larger renal masses with mass effect than those of IgG4-RD of the kidney.

Diffuse patchy infiltrative IgG4-RD of the kidney can mimic acute pyelonephritis, renal infarction, or renal sarcoidosis, which can manifest as multifocal round or wedge-shaped low-attenuation lesions in the renal cortex (Figs 12, 13) (23,34). Acute pyelonephritis should be considered in patients with fever and pyuria. Acute pyelonephritis generally involves a single kidney, but it can also be bilateral (35). Bilateral involvement is common in IgG4-RD of the kidney, but unilateral involvement cannot exclude the probability of IgG4-RD (22). Clinical correlation is essential for differential diagnosis. Renal infarction can be radiologically differentiated by the presence of the cortical rim sign (thin rim enhancement of the cortex due to collateral capsular perfusion) or flip-flop enhancement (a region of decreased enhancement during the early phase becomes hyperenhancement during the delayed phase) at CT (36). In rare cases, diffuse infiltrative renal malignant lesions including lymphoma, leukemia, and plasmacytoma can mimic diffuse infiltrative IgG4-RD of the kidney (37). The imaging finding of a single nodular lesion of IgG4-RD of the kidney is nonspecific, so there are many differential diagnoses including inflammatory, infectious, and neoplastic diseases such as renal cell carcinoma (particularly the papillary or chromophobe type) and the single nodular type of lymphoma (23). Pathologic confirmation at biopsy and clinical correlation are inevitable for the single nodular lesion.

Acute pyelonephritis in a 63-year-old woman with fever and chills.                         Axial contrast-enhanced CT image shows several ill-defined patchy                         hypoattenuating lesions (arrows) in the right kidney. Acute pyelonephritis                         was confirmed with clinical and laboratory findings.

Figure 12. Acute pyelonephritis in a 63-year-old woman with fever and chills. Axial contrast-enhanced CT image shows several ill-defined patchy hypoattenuating lesions (arrows) in the right kidney. Acute pyelonephritis was confirmed with clinical and laboratory findings.

Renal infarction in a 57-year-old woman with acute left flank pain.                         (a) Axial contrast-enhanced corticomedullary phase CT image shows a few                         wedge-shaped lesions with poor contrast material enhancement (arrows) in the                         left kidney. (b) Axial contrast-enhanced nephrographic phase CT image shows                         well-demarcated wedge-shaped lesions with poor contrast material enhancement                         (arrows) in the left kidney. The right kidney is mildly atrophied and shows                         a few small cortical scars, presumably caused by chronic                         pyelonephritis.

Figure 13a. Renal infarction in a 57-year-old woman with acute left flank pain. (a) Axial contrast-enhanced corticomedullary phase CT image shows a few wedge-shaped lesions with poor contrast material enhancement (arrows) in the left kidney. (b) Axial contrast-enhanced nephrographic phase CT image shows well-demarcated wedge-shaped lesions with poor contrast material enhancement (arrows) in the left kidney. The right kidney is mildly atrophied and shows a few small cortical scars, presumably caused by chronic pyelonephritis.

Renal infarction in a 57-year-old woman with acute left flank pain.                         (a) Axial contrast-enhanced corticomedullary phase CT image shows a few                         wedge-shaped lesions with poor contrast material enhancement (arrows) in the                         left kidney. (b) Axial contrast-enhanced nephrographic phase CT image shows                         well-demarcated wedge-shaped lesions with poor contrast material enhancement                         (arrows) in the left kidney. The right kidney is mildly atrophied and shows                         a few small cortical scars, presumably caused by chronic                         pyelonephritis.

Figure 13b. Renal infarction in a 57-year-old woman with acute left flank pain. (a) Axial contrast-enhanced corticomedullary phase CT image shows a few wedge-shaped lesions with poor contrast material enhancement (arrows) in the left kidney. (b) Axial contrast-enhanced nephrographic phase CT image shows well-demarcated wedge-shaped lesions with poor contrast material enhancement (arrows) in the left kidney. The right kidney is mildly atrophied and shows a few small cortical scars, presumably caused by chronic pyelonephritis.

IgG4-RD of the kidney involving the renal pelvis and/or renal sinus should be differentiated from urothelial cell carcinoma of the renal pelvis (Fig 14), lymphoma, Castleman disease, and nonspecific pyelitis (38). CT findings suggestive of IgG4-RD involving the renal pelvis and/or sinus compared with those of urothelial cell carcinoma are bilateral and longer urinary tract involvement, ill-defined margins, an extramural growth pattern, a gradual enhancement pattern at dynamic CT, and simultaneous involvement of IgG4-RD in other organs (39). The differential diagnosis of perinephric lesions includes renal lymphomas (Fig 15), leukemia, Erdheim-Chester disease (Fig 16), amyloidosis, non–IgG4–related retroperitoneal fibrosis, and extramedullary hematopoiesis (22,40,41).

Urothelial cell carcinoma of the left renal pelvis in a 76-year-old                         man with gross hematuria. (a) Axial contrast-enhanced nephrographic phase CT                         image shows an ill-defined infiltrative lesion involving the left renal                         pelvis (arrows), which mimics renal pelvis involvement of IgG4-RD of the                         kidney. (b) Axial contrast-enhanced excretory phase CT image shows irregular                         wall thickening of the left renal pelvis (arrows). Left nephroureterectomy                         confirmed high-grade urothelial cell carcinoma of the renal                         pelvis.

Figure 14a. Urothelial cell carcinoma of the left renal pelvis in a 76-year-old man with gross hematuria. (a) Axial contrast-enhanced nephrographic phase CT image shows an ill-defined infiltrative lesion involving the left renal pelvis (arrows), which mimics renal pelvis involvement of IgG4-RD of the kidney. (b) Axial contrast-enhanced excretory phase CT image shows irregular wall thickening of the left renal pelvis (arrows). Left nephroureterectomy confirmed high-grade urothelial cell carcinoma of the renal pelvis.

Urothelial cell carcinoma of the left renal pelvis in a 76-year-old                         man with gross hematuria. (a) Axial contrast-enhanced nephrographic phase CT                         image shows an ill-defined infiltrative lesion involving the left renal                         pelvis (arrows), which mimics renal pelvis involvement of IgG4-RD of the                         kidney. (b) Axial contrast-enhanced excretory phase CT image shows irregular                         wall thickening of the left renal pelvis (arrows). Left nephroureterectomy                         confirmed high-grade urothelial cell carcinoma of the renal                         pelvis.

Figure 14b. Urothelial cell carcinoma of the left renal pelvis in a 76-year-old man with gross hematuria. (a) Axial contrast-enhanced nephrographic phase CT image shows an ill-defined infiltrative lesion involving the left renal pelvis (arrows), which mimics renal pelvis involvement of IgG4-RD of the kidney. (b) Axial contrast-enhanced excretory phase CT image shows irregular wall thickening of the left renal pelvis (arrows). Left nephroureterectomy confirmed high-grade urothelial cell carcinoma of the renal pelvis.

Lymphoma involving the bilateral perinephric space in an 82-year-old                         woman with weight loss. (a) Coronal contrast-enhanced CT image shows a                         homogeneous rimlike soft-tissue mass surrounding both kidneys (arrows). (b)                         Coronal contrast-enhanced CT image also shows a diffuse infiltrative                         soft-tissue–attenuation lesion along the small bowel mesentery                         (arrows). Biopsy of the mediastinal lymph nodes confirmed extranodal                         marginal zone lymphoma of mucosa-associated lymphoid tissue.

Figure 15a. Lymphoma involving the bilateral perinephric space in an 82-year-old woman with weight loss. (a) Coronal contrast-enhanced CT image shows a homogeneous rimlike soft-tissue mass surrounding both kidneys (arrows). (b) Coronal contrast-enhanced CT image also shows a diffuse infiltrative soft-tissue–attenuation lesion along the small bowel mesentery (arrows). Biopsy of the mediastinal lymph nodes confirmed extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue.

Lymphoma involving the bilateral perinephric space in an 82-year-old                         woman with weight loss. (a) Coronal contrast-enhanced CT image shows a                         homogeneous rimlike soft-tissue mass surrounding both kidneys (arrows). (b)                         Coronal contrast-enhanced CT image also shows a diffuse infiltrative                         soft-tissue–attenuation lesion along the small bowel mesentery                         (arrows). Biopsy of the mediastinal lymph nodes confirmed extranodal                         marginal zone lymphoma of mucosa-associated lymphoid tissue.

Figure 15b. Lymphoma involving the bilateral perinephric space in an 82-year-old woman with weight loss. (a) Coronal contrast-enhanced CT image shows a homogeneous rimlike soft-tissue mass surrounding both kidneys (arrows). (b) Coronal contrast-enhanced CT image also shows a diffuse infiltrative soft-tissue–attenuation lesion along the small bowel mesentery (arrows). Biopsy of the mediastinal lymph nodes confirmed extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue.

Erdheim-Chester disease in a 45-year-old man who presented with                         impaired renal function. Axial contrast-enhanced corticomedullary phase (a)                         and excretory phase (b) CT images show bilateral and symmetric soft-tissue                         infiltration in the perirenal spaces (open arrows) and along the renal                         pelvis or sinus (solid arrows), causing mild hydronephrosis. Note the                         diffuse thickening of the right anterior renal fascia (arrowhead). US-guided                         biopsy results confirmed Erdheim-Chester disease.

Figure 16a. Erdheim-Chester disease in a 45-year-old man who presented with impaired renal function. Axial contrast-enhanced corticomedullary phase (a) and excretory phase (b) CT images show bilateral and symmetric soft-tissue infiltration in the perirenal spaces (open arrows) and along the renal pelvis or sinus (solid arrows), causing mild hydronephrosis. Note the diffuse thickening of the right anterior renal fascia (arrowhead). US-guided biopsy results confirmed Erdheim-Chester disease.

Erdheim-Chester disease in a 45-year-old man who presented with                         impaired renal function. Axial contrast-enhanced corticomedullary phase (a)                         and excretory phase (b) CT images show bilateral and symmetric soft-tissue                         infiltration in the perirenal spaces (open arrows) and along the renal                         pelvis or sinus (solid arrows), causing mild hydronephrosis. Note the                         diffuse thickening of the right anterior renal fascia (arrowhead). US-guided                         biopsy results confirmed Erdheim-Chester disease.

Figure 16b. Erdheim-Chester disease in a 45-year-old man who presented with impaired renal function. Axial contrast-enhanced corticomedullary phase (a) and excretory phase (b) CT images show bilateral and symmetric soft-tissue infiltration in the perirenal spaces (open arrows) and along the renal pelvis or sinus (solid arrows), causing mild hydronephrosis. Note the diffuse thickening of the right anterior renal fascia (arrowhead). US-guided biopsy results confirmed Erdheim-Chester disease.

Imaging Findings during Treatment and Follow-up.—IgG4-RD of the kidney usually shows a rapid and favorable response to steroid treatment, regardless of the lesion location (Fig 8). During the treatment, the lesion size and number dramatically decrease. Renal parenchymal enhancement recovered after treatment in almost all patients in one longitudinal imaging study (42). However, some areas of the kidney can undergo atrophic scarring (Fig 4), even when the patient has responded well to therapy (42). Without steroid treatment, the renal lesions can increase in size and number or progress to diffuse patchy infiltrative involvement (22). IgG4-RD of the kidney can relapse in up to 20% of patients, mainly during maintenance therapy or after cessation of steroid therapy (22,23). In some cases of IgG4-RD without renal involvement, renal parenchymal lesions can newly develop as a recurrence of the disease during maintenance steroid therapy. Since the kidneys are among the organs most frequently affected by this disease, Kawano et al (43) proposed annual imaging follow-up, even if the kidney is not involved at the first diagnosis. However, to the best of our knowledge, there is no international consensus or guideline for the surveillance imaging of IgG4-RD of the kidney.

IgG4-RD of the Ureter

IgG4-RD involving the ureter is rare and only 16 cases were found in one literature survey published at 2018 (44). Ureteral IgG4-RDs had been reported as “inflammatory pseudotumors” or “idiopathic segmental ureteritis” before the introduction of the term IgG4-RD (45). The mean age of patients with ureteral IgG4-RD was 60 years and the age range was wide (13–84 years). Men were affected more frequently than were women (male-to-female ratio, 4:1) (45,46). The size of ureteral lesions was 1–4 cm in greatest dimension (average size, 2.6 cm). Clinical manifestations of ureteral IgG4-RD vary from incidental radiologic findings to ureteral obstructive symptoms including flank pain, hematuria, proteinuria, and renal dysfunction and overlap with those of IgG4-RD of the kidney (46,47). Ureteral IgG4-RD reported so far has been typically diagnosed after surgical resection because it cannot be easily differentiated from urothelial carcinoma at radiologic evaluation (47).

Teaching Point Ureteral IgG4-RD can be classified into three types on the basis of gross morphologic features: polypoid mass-forming lesions, segmental ureteral wall thickening, and periureteral fibrosis.
Obstructive hydroureteronephrosis is usually associated because of mass effect, regardless of the lesion location along the ureter (46).

Ureteral IgG4-RD can manifest as a solitary well-defined polypoid enhancing mass (inflammatory pseudotumor) that obstructs the ureter lumen (Fig 17). Although renal lesions in IgG4-RD were reported to show diffusion restriction at diffusion-weighted MRI, the polypoid mass of ureteral IgG4-RD in the patient in Figure 17 did not show substantial diffusion restriction at diffusion-weighted MRI (not shown). The usefulness of diffusion-weighted imaging in the diagnosis of ureteral IgG4-RD should be further evaluated in the future. The differential diagnosis of polypoid ureteral IgG4-RD includes ureteral urothelial cell carcinoma (Fig 18), papilloma, and fibroepithelial polyp (46,48).

IgG4-RD of the ureter manifesting as a polypoid mass-forming lesion in                         a 22-year-old man who presented with impaired renal function. His creatinine                         level was 1.67 mg/dL (147.63 μmol/L) and his serum IgG4 level was 118                         mg/dL (1.18 g/L), with a reference range of 3.9–86.4 mg/dL                         (0.04–0.86 g/L). Coronal T2-weighted (a) and contrast-enhanced                         T1-weighted (b) MR images show a well-defined polypoid intraluminal mass                         (arrow) in the left distal ureter, which appears as a hypointensity in a and                         as a homogeneously enhancing lesion in b. Laparoscopic excision of the                         ureteral mass and end-to-end anastomosis of the ureter were performed. The                         diagnosis was confirmed at pathologic evaluation as IgG4-RD, manifesting as                         an inflammatory pseudotumor. B = urinary bladder.

Figure 17a. IgG4-RD of the ureter manifesting as a polypoid mass-forming lesion in a 22-year-old man who presented with impaired renal function. His creatinine level was 1.67 mg/dL (147.63 μmol/L) and his serum IgG4 level was 118 mg/dL (1.18 g/L), with a reference range of 3.9–86.4 mg/dL (0.04–0.86 g/L). Coronal T2-weighted (a) and contrast-enhanced T1-weighted (b) MR images show a well-defined polypoid intraluminal mass (arrow) in the left distal ureter, which appears as a hypointensity in a and as a homogeneously enhancing lesion in b. Laparoscopic excision of the ureteral mass and end-to-end anastomosis of the ureter were performed. The diagnosis was confirmed at pathologic evaluation as IgG4-RD, manifesting as an inflammatory pseudotumor. B = urinary bladder.

IgG4-RD of the ureter manifesting as a polypoid mass-forming lesion in                         a 22-year-old man who presented with impaired renal function. His creatinine                         level was 1.67 mg/dL (147.63 μmol/L) and his serum IgG4 level was 118                         mg/dL (1.18 g/L), with a reference range of 3.9–86.4 mg/dL                         (0.04–0.86 g/L). Coronal T2-weighted (a) and contrast-enhanced                         T1-weighted (b) MR images show a well-defined polypoid intraluminal mass                         (arrow) in the left distal ureter, which appears as a hypointensity in a and                         as a homogeneously enhancing lesion in b. Laparoscopic excision of the                         ureteral mass and end-to-end anastomosis of the ureter were performed. The                         diagnosis was confirmed at pathologic evaluation as IgG4-RD, manifesting as                         an inflammatory pseudotumor. B = urinary bladder.

Figure 17b. IgG4-RD of the ureter manifesting as a polypoid mass-forming lesion in a 22-year-old man who presented with impaired renal function. His creatinine level was 1.67 mg/dL (147.63 μmol/L) and his serum IgG4 level was 118 mg/dL (1.18 g/L), with a reference range of 3.9–86.4 mg/dL (0.04–0.86 g/L). Coronal T2-weighted (a) and contrast-enhanced T1-weighted (b) MR images show a well-defined polypoid intraluminal mass (arrow) in the left distal ureter, which appears as a hypointensity in a and as a homogeneously enhancing lesion in b. Laparoscopic excision of the ureteral mass and end-to-end anastomosis of the ureter were performed. The diagnosis was confirmed at pathologic evaluation as IgG4-RD, manifesting as an inflammatory pseudotumor. B = urinary bladder.

Urothelial cell carcinoma of the left distal ureter in a 79-year-old                         man with gross hematuria. Sagittal contrast-enhanced CT image shows a                         homogeneously enhancing polypoid mass (arrows) and hydroureter (arrowheads).                         Left nephroureterectomy allowed confirmation of the diagnosis of urothelial                         cell carcinoma of the ureter.

Figure 18. Urothelial cell carcinoma of the left distal ureter in a 79-year-old man with gross hematuria. Sagittal contrast-enhanced CT image shows a homogeneously enhancing polypoid mass (arrows) and hydroureter (arrowheads). Left nephroureterectomy allowed confirmation of the diagnosis of urothelial cell carcinoma of the ureter.

Segmental ureteral wall thickening (idiopathic segmental ureteritis) is another manifestation of ureteral IgG4-RD. Ureteral wall thickening often arises by the extension from the renal pelvic wall thickening of IgG4-RD of the kidney. However, segmental ureteral wall thickening without a renal pelvic lesion was also reported (49). Segmental concentric ureteral wall thickening causes ureteral narrowing and hydronephrosis at CT (Fig 19).

IgG4-RD of the ureter manifesting as segmental ureteral wall                         thickening in a 24-year-old man with right flank discomfort. (a, b) Coronal                         contrast-enhanced CT images show segmental ureteral wall thickening, with                         ureteral luminal narrowing (arrows in a) and obstructive hydronephrosis                         (arrowhead in b). Right nephroureterectomy with bladder cuff excision was                         performed because of suspicion for urothelial cell carcinoma. (c) Photograph                         of the gross specimen shows encircling ureteral wall thickening with                         stenosis (arrows). Microscopic examination (not shown) confirmed IgG4-RD                         involving the ureter, manifesting as sclerosing ureteritis. The serum IgG4                         level obtained after surgery was 1360 mg/dL (13.6 g/L), with a reference                         range of 3.9–86.4 mg/dL (0.04–0.86 g/L).

Figure 19a. IgG4-RD of the ureter manifesting as segmental ureteral wall thickening in a 24-year-old man with right flank discomfort. (a, b) Coronal contrast-enhanced CT images show segmental ureteral wall thickening, with ureteral luminal narrowing (arrows in a) and obstructive hydronephrosis (arrowhead in b). Right nephroureterectomy with bladder cuff excision was performed because of suspicion for urothelial cell carcinoma. (c) Photograph of the gross specimen shows encircling ureteral wall thickening with stenosis (arrows). Microscopic examination (not shown) confirmed IgG4-RD involving the ureter, manifesting as sclerosing ureteritis. The serum IgG4 level obtained after surgery was 1360 mg/dL (13.6 g/L), with a reference range of 3.9–86.4 mg/dL (0.04–0.86 g/L).

IgG4-RD of the ureter manifesting as segmental ureteral wall                         thickening in a 24-year-old man with right flank discomfort. (a, b) Coronal                         contrast-enhanced CT images show segmental ureteral wall thickening, with                         ureteral luminal narrowing (arrows in a) and obstructive hydronephrosis                         (arrowhead in b). Right nephroureterectomy with bladder cuff excision was                         performed because of suspicion for urothelial cell carcinoma. (c) Photograph                         of the gross specimen shows encircling ureteral wall thickening with                         stenosis (arrows). Microscopic examination (not shown) confirmed IgG4-RD                         involving the ureter, manifesting as sclerosing ureteritis. The serum IgG4                         level obtained after surgery was 1360 mg/dL (13.6 g/L), with a reference                         range of 3.9–86.4 mg/dL (0.04–0.86 g/L).

Figure 19b. IgG4-RD of the ureter manifesting as segmental ureteral wall thickening in a 24-year-old man with right flank discomfort. (a, b) Coronal contrast-enhanced CT images show segmental ureteral wall thickening, with ureteral luminal narrowing (arrows in a) and obstructive hydronephrosis (arrowhead in b). Right nephroureterectomy with bladder cuff excision was performed because of suspicion for urothelial cell carcinoma. (c) Photograph of the gross specimen shows encircling ureteral wall thickening with stenosis (arrows). Microscopic examination (not shown) confirmed IgG4-RD involving the ureter, manifesting as sclerosing ureteritis. The serum IgG4 level obtained after surgery was 1360 mg/dL (13.6 g/L), with a reference range of 3.9–86.4 mg/dL (0.04–0.86 g/L).

IgG4-RD of the ureter manifesting as segmental ureteral wall                         thickening in a 24-year-old man with right flank discomfort. (a, b) Coronal                         contrast-enhanced CT images show segmental ureteral wall thickening, with                         ureteral luminal narrowing (arrows in a) and obstructive hydronephrosis                         (arrowhead in b). Right nephroureterectomy with bladder cuff excision was                         performed because of suspicion for urothelial cell carcinoma. (c) Photograph                         of the gross specimen shows encircling ureteral wall thickening with                         stenosis (arrows). Microscopic examination (not shown) confirmed IgG4-RD                         involving the ureter, manifesting as sclerosing ureteritis. The serum IgG4                         level obtained after surgery was 1360 mg/dL (13.6 g/L), with a reference                         range of 3.9–86.4 mg/dL (0.04–0.86 g/L).

Figure 19c. IgG4-RD of the ureter manifesting as segmental ureteral wall thickening in a 24-year-old man with right flank discomfort. (a, b) Coronal contrast-enhanced CT images show segmental ureteral wall thickening, with ureteral luminal narrowing (arrows in a) and obstructive hydronephrosis (arrowhead in b). Right nephroureterectomy with bladder cuff excision was performed because of suspicion for urothelial cell carcinoma. (c) Photograph of the gross specimen shows encircling ureteral wall thickening with stenosis (arrows). Microscopic examination (not shown) confirmed IgG4-RD involving the ureter, manifesting as sclerosing ureteritis. The serum IgG4 level obtained after surgery was 1360 mg/dL (13.6 g/L), with a reference range of 3.9–86.4 mg/dL (0.04–0.86 g/L).

The third manifestation of ureteral IgG4-RD is periureteral fibrosis with disease epicenters in the periureteral adipose tissue. At pathologic evaluation, a periureteral fibroinflammatory mass may be seen without ureter wall involvement (46), but the ureter wall can be secondarily involved as an inward extension of periureteral fibrosis (Fig 20). Periureteral fibrosis can result from IgG4-RD retroperitoneal fibrosis. Discrimination between the segmental ureteral wall thickening and periureteral fibrosis at imaging is difficult and may be possible only at histopathologic analysis. The differential diagnosis of ureteral wall thickening and periureteral fibrosis includes urothelial cell carcinoma and other causes of benign ureteral stricture. All three cases of ureteral IgG4-RD in our institution had no other organ involvement, which made it difficult to diagnose IgG4-RD preoperatively. Diagnostic ureteropyeloscopy and tissue biopsy can help to diagnose upper urinary tract cancer or to rule out malignancy for patients with negative voiding cytology findings (50).

IgG4-RD of the ureter manifesting as periureteral fibrosis in a                         56-year-old man with left flank pain. (a) Coronal excretory phase                         contrast-enhanced CT image shows tapering of the left ureter by the                         2.8-cm-long bulging mass-forming lesion (arrows) with soft-tissue                         attenuation and upstream ureteral dilatation. LK = left kidney. Left                         nephroureterectomy with bladder cuff excision was performed. (b) Photograph                         of the gross specimen shows the periureteral fibrotic mass (arrows) and                         intact smooth ureteral wall (arrowheads). Microscopic examination (not                         shown) revealed periureteric follicular lymphoid hyperplasia with increased                         IgG4 cells, which is suggestive of IgG4-RD.

Figure 20a. IgG4-RD of the ureter manifesting as periureteral fibrosis in a 56-year-old man with left flank pain. (a) Coronal excretory phase contrast-enhanced CT image shows tapering of the left ureter by the 2.8-cm-long bulging mass-forming lesion (arrows) with soft-tissue attenuation and upstream ureteral dilatation. LK = left kidney. Left nephroureterectomy with bladder cuff excision was performed. (b) Photograph of the gross specimen shows the periureteral fibrotic mass (arrows) and intact smooth ureteral wall (arrowheads). Microscopic examination (not shown) revealed periureteric follicular lymphoid hyperplasia with increased IgG4 cells, which is suggestive of IgG4-RD.

IgG4-RD of the ureter manifesting as periureteral fibrosis in a                         56-year-old man with left flank pain. (a) Coronal excretory phase                         contrast-enhanced CT image shows tapering of the left ureter by the                         2.8-cm-long bulging mass-forming lesion (arrows) with soft-tissue                         attenuation and upstream ureteral dilatation. LK = left kidney. Left                         nephroureterectomy with bladder cuff excision was performed. (b) Photograph                         of the gross specimen shows the periureteral fibrotic mass (arrows) and                         intact smooth ureteral wall (arrowheads). Microscopic examination (not                         shown) revealed periureteric follicular lymphoid hyperplasia with increased                         IgG4 cells, which is suggestive of IgG4-RD.

Figure 20b. IgG4-RD of the ureter manifesting as periureteral fibrosis in a 56-year-old man with left flank pain. (a) Coronal excretory phase contrast-enhanced CT image shows tapering of the left ureter by the 2.8-cm-long bulging mass-forming lesion (arrows) with soft-tissue attenuation and upstream ureteral dilatation. LK = left kidney. Left nephroureterectomy with bladder cuff excision was performed. (b) Photograph of the gross specimen shows the periureteral fibrotic mass (arrows) and intact smooth ureteral wall (arrowheads). Microscopic examination (not shown) revealed periureteric follicular lymphoid hyperplasia with increased IgG4 cells, which is suggestive of IgG4-RD.

IgG4-RD Retroperitoneal Fibrosis

Retroperitoneal fibrosis is a fibroinflammatory disease that develops around the abdominal aorta and the iliac arteries and spreads into the adjacent retroperitoneum. It can be either idiopathic (>75% of cases) or secondary to infections, malignancies, drugs, or other conditions (51,52). IgG4-RD is the cause of up to two-thirds of cases of idiopathic retroperitoneal fibrosis (15,53). Ureteral involvement is the most common complication of retroperitoneal fibrosis, which usually causes medial deviation of the ureter and/or obstruction by extrinsic compression (51). Ureteral encasement can be unilateral or bilateral. At imaging, it is difficult to differentiate IgG4-RD retroperitoneal fibrosis from other causes (15). Typical imaging findings of idiopathic retroperitoneal fibrosis are a well-demarcated but irregular soft-tissue mass or plaque surrounding the anterolateral sides of the abdominal aorta and its major branches (Fig 21). The involved aortic segment tends to be the infrarenal aorta, often extending to the iliac vessels (17). CT shows homogeneous soft-tissue attenuation similar to that of the muscle. T1-weighted MRI shows low signal intensity, and T2-weighted MRI shows variable signal intensity. The signal intensity at T2-weighted MRI and the degree of contrast material enhancement may be variable depending on the degree of active inflammation and the maturity of fibrous tissue (4,54). FDG PET/CT is a useful tool for assessment of retroperitoneal fibrosis activity and metabolic activity of posttreatment residual disease (51).

IgG4-RD retroperitoneal fibrosis in a 73-year-old woman with pain in                         the left lower quadrant of the abdomen. (a, b) Axial contrast-enhanced CT                         images at the level of the inferior mesenteric artery (a) and the common                         iliac artery (b) show a circumferential homogeneously enhancing lesion                         (arrowheads) with soft-tissue attenuation surrounding the abdominal aorta                         and bilateral common iliac arteries. (c) Axial contrast-enhanced CT image at                         the level of the kidney shows mild hydronephrosis of the left kidney                         (arrow). Surgical biopsy results of the retroperitoneal lesion confirmed                         IgG4-RD retroperitoneal fibrosis.

Figure 21a. IgG4-RD retroperitoneal fibrosis in a 73-year-old woman with pain in the left lower quadrant of the abdomen. (a, b) Axial contrast-enhanced CT images at the level of the inferior mesenteric artery (a) and the common iliac artery (b) show a circumferential homogeneously enhancing lesion (arrowheads) with soft-tissue attenuation surrounding the abdominal aorta and bilateral common iliac arteries. (c) Axial contrast-enhanced CT image at the level of the kidney shows mild hydronephrosis of the left kidney (arrow). Surgical biopsy results of the retroperitoneal lesion confirmed IgG4-RD retroperitoneal fibrosis.

IgG4-RD retroperitoneal fibrosis in a 73-year-old woman with pain in                         the left lower quadrant of the abdomen. (a, b) Axial contrast-enhanced CT                         images at the level of the inferior mesenteric artery (a) and the common                         iliac artery (b) show a circumferential homogeneously enhancing lesion                         (arrowheads) with soft-tissue attenuation surrounding the abdominal aorta                         and bilateral common iliac arteries. (c) Axial contrast-enhanced CT image at                         the level of the kidney shows mild hydronephrosis of the left kidney                         (arrow). Surgical biopsy results of the retroperitoneal lesion confirmed                         IgG4-RD retroperitoneal fibrosis.

Figure 21b. IgG4-RD retroperitoneal fibrosis in a 73-year-old woman with pain in the left lower quadrant of the abdomen. (a, b) Axial contrast-enhanced CT images at the level of the inferior mesenteric artery (a) and the common iliac artery (b) show a circumferential homogeneously enhancing lesion (arrowheads) with soft-tissue attenuation surrounding the abdominal aorta and bilateral common iliac arteries. (c) Axial contrast-enhanced CT image at the level of the kidney shows mild hydronephrosis of the left kidney (arrow). Surgical biopsy results of the retroperitoneal lesion confirmed IgG4-RD retroperitoneal fibrosis.

IgG4-RD retroperitoneal fibrosis in a 73-year-old woman with pain in                         the left lower quadrant of the abdomen. (a, b) Axial contrast-enhanced CT                         images at the level of the inferior mesenteric artery (a) and the common                         iliac artery (b) show a circumferential homogeneously enhancing lesion                         (arrowheads) with soft-tissue attenuation surrounding the abdominal aorta                         and bilateral common iliac arteries. (c) Axial contrast-enhanced CT image at                         the level of the kidney shows mild hydronephrosis of the left kidney                         (arrow). Surgical biopsy results of the retroperitoneal lesion confirmed                         IgG4-RD retroperitoneal fibrosis.

Figure 21c. IgG4-RD retroperitoneal fibrosis in a 73-year-old woman with pain in the left lower quadrant of the abdomen. (a, b) Axial contrast-enhanced CT images at the level of the inferior mesenteric artery (a) and the common iliac artery (b) show a circumferential homogeneously enhancing lesion (arrowheads) with soft-tissue attenuation surrounding the abdominal aorta and bilateral common iliac arteries. (c) Axial contrast-enhanced CT image at the level of the kidney shows mild hydronephrosis of the left kidney (arrow). Surgical biopsy results of the retroperitoneal lesion confirmed IgG4-RD retroperitoneal fibrosis.

IgG4-RD of the Bladder

Urinary bladder involvement of IgG4-RD is rare compared with kidney involvement. There are a few case reports (9,5559) of isolated IgG4-RD of the bladder. Although scarcely reported, there are various manifestations of IgG4-RD involving the bladder, including transmural bladder wall thickening, intravesical polypoid bladder masses, and extraluminal perivesical or periurethral masses. No patients in our institution had bladder involvement of IgG4-RD between January 2010 and December 2018.

Park et al (55) reported that the first known case of IgG4-RD involving the bladder manifested as transmural bladder wall thickening. A 72-year-old woman presented with painless hematuria. At CT, an enhancing mass that appeared to be centered in the bladder wall was adherent to the sigmoid colon. Urinalysis results showed evidence of fecal material, supporting the clinical diagnosis of invasive bladder cancer or sigmoid colon cancer with a vesicosigmoid fistula. A partial cystectomy with segmental resection of the adherent sigmoid colon was performed, and pathologic examination confirmed IgG4-RD involving the bladder.

Bladder IgG4-RD can manifest as an intravesical polypoid mass, which may mimic bladder cancer, or a subepithelial tumor such as a leiomyoma. A case report (57) of IgG4-RD involving the bladder showed a well-defined polypoid mass arising from the bladder wall and showing low signal intensity at T2-weighted MRI. Transurethral resection of the mass allowed confirmation of bladder IgG4-RD, which was confined to the subepithelial layer of the bladder (57).

Sangsoad et al reported (59) on a case of bladder and urethral IgG4-RD that manifested as an extravesical and periurethral lesion. The patient had a huge inflammatory pseudotumor in the bladder neck and the periurethral region, which resembled, at first glance, a prostate gland in a female patient. The mass was seen as a large well-defined round lesion with homogeneous intermediate signal intensity at T2-weighted MRI. IgG4-RD was not included in the preoperative differential diagnosis in most of the reported cases of bladder IgG4-RD. It is not easy to diagnose IgG4-RD involving the bladder preoperatively, especially without other organ involvement.

IgG4-RD of the Prostate Gland

IgG4-RD involving the prostate gland has also been reported (60). Most patients reported in the literature were diagnosed retrospectively with IgG4-RD prostatitis on the basis of histopathologic findings after transurethral resection for the symptoms of benign prostatic hyperplasia (60). Also, the presumptive diagnosis of IgG4-RD prostatitis is commonly made on the basis of the presence of IgG4-RD involving other organs and abrupt symptomatic relief of benign prostatic hyperplasia after glucocorticoid treatment (5). Biopsy-proven mass-forming IgG4-RD of the prostate gland has also been reported (61). Serum prostate-specific antigen levels in IgG4-RD involving the prostate tend to be low because the prostate ducts often convert to fibrosis (10). IgG4-RD prostatitis can occur simultaneously with prostatic adenocarcinoma (62).

To date, data on imaging manifestations of IgG4-RD of the prostate gland are limited. Only a few case reports (61,63) briefly mentioned CT findings as diffuse enlargement of the prostate gland with homogeneous low attenuation. We experienced two types of radiologic manifestations of IgG4-RD involving the prostate gland, which are diffuse infiltrative prostatitis and periprostatic mass-forming lesions. A 54-year-old man with voiding difficulty showed diffuse enlargement of the prostate gland, with loss of zonal anatomy at US and MRI (Fig 22). CT showed a soft-tissue infiltrative lesion encasing the left renal pelvis and sinus. After administration of corticosteroid treatment, CT revealed improved prostatic enlargement and an infiltrative lesion in the left renal pelvis and sinus. In another case, a 61-year-old man with flank pain showed bilateral symmetric periprostatic mass-forming lesions at US and MRI that were proven to be IgG4-RD by transrectal US-guided biopsy (Fig 23). This patient had bilateral renal pelvis and sinus involvement of IgG4-RD. Because IgG4-RD typically responds well to corticosteroid treatment, it is important to differentiate prostate IgG4-RD from prostate cancer and other prostatitis. Imaging and clinical findings of prostate IgG4-RD are nonspecific, so the diagnosis is reliant on biopsy results and response to steroid treatment. If there are simultaneous findings of IgG4-RD in other organs, IgG4-RD should be considered in the differential diagnosis (Figs 22, 23).

Diffuse infiltrative IgG4-RD of the prostate in a 54-year-old man with                         voiding difficulty. His serum IgG4 level was 352 mg/dL (3.52 g/L) with a                         reference range of 3.9–86.4 mg/dL (0.04–0.86 g/L). (a)                         Transrectal US image shows diffuse enlargement of the prostate gland,                         without a focal lesion. (b) Axial T2-weighted MR image also shows diffuse                         enlargement and loss of normal zonal anatomy of the prostate gland. Mild                         diffusion restriction was present in the prostate gland on                         diffusion-weighted MR images (not shown). (c) Axial contrast-enhanced                         excretory phase CT image shows a mildly enhancing soft-tissue infiltrative                         lesion (arrows) encasing the left renal pelvis and sinus. IgG4-RD                         prostatitis was pathologically confirmed after transrectal US-guided core                         biopsy of the prostate. Both prostatic enlargement and renal pelvic or sinus                         lesions were improved after steroid treatment.

Figure 22a. Diffuse infiltrative IgG4-RD of the prostate in a 54-year-old man with voiding difficulty. His serum IgG4 level was 352 mg/dL (3.52 g/L) with a reference range of 3.9–86.4 mg/dL (0.04–0.86 g/L). (a) Transrectal US image shows diffuse enlargement of the prostate gland, without a focal lesion. (b) Axial T2-weighted MR image also shows diffuse enlargement and loss of normal zonal anatomy of the prostate gland. Mild diffusion restriction was present in the prostate gland on diffusion-weighted MR images (not shown). (c) Axial contrast-enhanced excretory phase CT image shows a mildly enhancing soft-tissue infiltrative lesion (arrows) encasing the left renal pelvis and sinus. IgG4-RD prostatitis was pathologically confirmed after transrectal US-guided core biopsy of the prostate. Both prostatic enlargement and renal pelvic or sinus lesions were improved after steroid treatment.

Diffuse infiltrative IgG4-RD of the prostate in a 54-year-old man with                         voiding difficulty. His serum IgG4 level was 352 mg/dL (3.52 g/L) with a                         reference range of 3.9–86.4 mg/dL (0.04–0.86 g/L). (a)                         Transrectal US image shows diffuse enlargement of the prostate gland,                         without a focal lesion. (b) Axial T2-weighted MR image also shows diffuse                         enlargement and loss of normal zonal anatomy of the prostate gland. Mild                         diffusion restriction was present in the prostate gland on                         diffusion-weighted MR images (not shown). (c) Axial contrast-enhanced                         excretory phase CT image shows a mildly enhancing soft-tissue infiltrative                         lesion (arrows) encasing the left renal pelvis and sinus. IgG4-RD                         prostatitis was pathologically confirmed after transrectal US-guided core                         biopsy of the prostate. Both prostatic enlargement and renal pelvic or sinus                         lesions were improved after steroid treatment.

Figure 22b. Diffuse infiltrative IgG4-RD of the prostate in a 54-year-old man with voiding difficulty. His serum IgG4 level was 352 mg/dL (3.52 g/L) with a reference range of 3.9–86.4 mg/dL (0.04–0.86 g/L). (a) Transrectal US image shows diffuse enlargement of the prostate gland, without a focal lesion. (b) Axial T2-weighted MR image also shows diffuse enlargement and loss of normal zonal anatomy of the prostate gland. Mild diffusion restriction was present in the prostate gland on diffusion-weighted MR images (not shown). (c) Axial contrast-enhanced excretory phase CT image shows a mildly enhancing soft-tissue infiltrative lesion (arrows) encasing the left renal pelvis and sinus. IgG4-RD prostatitis was pathologically confirmed after transrectal US-guided core biopsy of the prostate. Both prostatic enlargement and renal pelvic or sinus lesions were improved after steroid treatment.

Diffuse infiltrative IgG4-RD of the prostate in a 54-year-old man with                         voiding difficulty. His serum IgG4 level was 352 mg/dL (3.52 g/L) with a                         reference range of 3.9–86.4 mg/dL (0.04–0.86 g/L). (a)                         Transrectal US image shows diffuse enlargement of the prostate gland,                         without a focal lesion. (b) Axial T2-weighted MR image also shows diffuse                         enlargement and loss of normal zonal anatomy of the prostate gland. Mild                         diffusion restriction was present in the prostate gland on                         diffusion-weighted MR images (not shown). (c) Axial contrast-enhanced                         excretory phase CT image shows a mildly enhancing soft-tissue infiltrative                         lesion (arrows) encasing the left renal pelvis and sinus. IgG4-RD                         prostatitis was pathologically confirmed after transrectal US-guided core                         biopsy of the prostate. Both prostatic enlargement and renal pelvic or sinus                         lesions were improved after steroid treatment.

Figure 22c. Diffuse infiltrative IgG4-RD of the prostate in a 54-year-old man with voiding difficulty. His serum IgG4 level was 352 mg/dL (3.52 g/L) with a reference range of 3.9–86.4 mg/dL (0.04–0.86 g/L). (a) Transrectal US image shows diffuse enlargement of the prostate gland, without a focal lesion. (b) Axial T2-weighted MR image also shows diffuse enlargement and loss of normal zonal anatomy of the prostate gland. Mild diffusion restriction was present in the prostate gland on diffusion-weighted MR images (not shown). (c) Axial contrast-enhanced excretory phase CT image shows a mildly enhancing soft-tissue infiltrative lesion (arrows) encasing the left renal pelvis and sinus. IgG4-RD prostatitis was pathologically confirmed after transrectal US-guided core biopsy of the prostate. Both prostatic enlargement and renal pelvic or sinus lesions were improved after steroid treatment.

IgG4-RD of the prostate gland, manifesting as a periprostatic                         mass-forming lesion in a 61-year-old man with flank pain. (a) Axial                         contrast-enhanced CT image at the midgland level shows bilateral enhancing                         lesions (solid arrows) surrounding the prostate gland (open arrows).                         (b–d) Consecutive transrectal US images of the prostate gland from                         the prostate base level (b) to the midgland level (c, d) show bilateral                         symmetric hypoechoic masslike lesions (solid arrows) surrounding the                         prostate gland (open arrows). Transrectal US image at the midgland level (d)                         shows the normal zonal anatomy of the central gland (CG) and peripheral zone                         (PZ). (e) Transrectal US-guided biopsy was performed through both                         periprostatic mass-forming lesions and the prostate tissue. (f)                         Photomicrograph shows a clear distinction (arrows) between the tissue from                         the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and                         the tissue from the prostate gland (p), with the normally preserved prostate                         gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g)                         Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid                         soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT                         image shows ill-defined mildly enhancing soft-tissue infiltrative lesions                         (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both                         periprostatic lesions and peripelvic lesions regressed after steroid                         treatment (not shown).

Figure 23a. IgG4-RD of the prostate gland, manifesting as a periprostatic mass-forming lesion in a 61-year-old man with flank pain. (a) Axial contrast-enhanced CT image at the midgland level shows bilateral enhancing lesions (solid arrows) surrounding the prostate gland (open arrows). (b–d) Consecutive transrectal US images of the prostate gland from the prostate base level (b) to the midgland level (c, d) show bilateral symmetric hypoechoic masslike lesions (solid arrows) surrounding the prostate gland (open arrows). Transrectal US image at the midgland level (d) shows the normal zonal anatomy of the central gland (CG) and peripheral zone (PZ). (e) Transrectal US-guided biopsy was performed through both periprostatic mass-forming lesions and the prostate tissue. (f) Photomicrograph shows a clear distinction (arrows) between the tissue from the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and the tissue from the prostate gland (p), with the normally preserved prostate gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g) Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT image shows ill-defined mildly enhancing soft-tissue infiltrative lesions (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both periprostatic lesions and peripelvic lesions regressed after steroid treatment (not shown).

IgG4-RD of the prostate gland, manifesting as a periprostatic                         mass-forming lesion in a 61-year-old man with flank pain. (a) Axial                         contrast-enhanced CT image at the midgland level shows bilateral enhancing                         lesions (solid arrows) surrounding the prostate gland (open arrows).                         (b–d) Consecutive transrectal US images of the prostate gland from                         the prostate base level (b) to the midgland level (c, d) show bilateral                         symmetric hypoechoic masslike lesions (solid arrows) surrounding the                         prostate gland (open arrows). Transrectal US image at the midgland level (d)                         shows the normal zonal anatomy of the central gland (CG) and peripheral zone                         (PZ). (e) Transrectal US-guided biopsy was performed through both                         periprostatic mass-forming lesions and the prostate tissue. (f)                         Photomicrograph shows a clear distinction (arrows) between the tissue from                         the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and                         the tissue from the prostate gland (p), with the normally preserved prostate                         gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g)                         Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid                         soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT                         image shows ill-defined mildly enhancing soft-tissue infiltrative lesions                         (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both                         periprostatic lesions and peripelvic lesions regressed after steroid                         treatment (not shown).

Figure 23b. IgG4-RD of the prostate gland, manifesting as a periprostatic mass-forming lesion in a 61-year-old man with flank pain. (a) Axial contrast-enhanced CT image at the midgland level shows bilateral enhancing lesions (solid arrows) surrounding the prostate gland (open arrows). (b–d) Consecutive transrectal US images of the prostate gland from the prostate base level (b) to the midgland level (c, d) show bilateral symmetric hypoechoic masslike lesions (solid arrows) surrounding the prostate gland (open arrows). Transrectal US image at the midgland level (d) shows the normal zonal anatomy of the central gland (CG) and peripheral zone (PZ). (e) Transrectal US-guided biopsy was performed through both periprostatic mass-forming lesions and the prostate tissue. (f) Photomicrograph shows a clear distinction (arrows) between the tissue from the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and the tissue from the prostate gland (p), with the normally preserved prostate gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g) Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT image shows ill-defined mildly enhancing soft-tissue infiltrative lesions (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both periprostatic lesions and peripelvic lesions regressed after steroid treatment (not shown).

IgG4-RD of the prostate gland, manifesting as a periprostatic                         mass-forming lesion in a 61-year-old man with flank pain. (a) Axial                         contrast-enhanced CT image at the midgland level shows bilateral enhancing                         lesions (solid arrows) surrounding the prostate gland (open arrows).                         (b–d) Consecutive transrectal US images of the prostate gland from                         the prostate base level (b) to the midgland level (c, d) show bilateral                         symmetric hypoechoic masslike lesions (solid arrows) surrounding the                         prostate gland (open arrows). Transrectal US image at the midgland level (d)                         shows the normal zonal anatomy of the central gland (CG) and peripheral zone                         (PZ). (e) Transrectal US-guided biopsy was performed through both                         periprostatic mass-forming lesions and the prostate tissue. (f)                         Photomicrograph shows a clear distinction (arrows) between the tissue from                         the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and                         the tissue from the prostate gland (p), with the normally preserved prostate                         gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g)                         Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid                         soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT                         image shows ill-defined mildly enhancing soft-tissue infiltrative lesions                         (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both                         periprostatic lesions and peripelvic lesions regressed after steroid                         treatment (not shown).

Figure 23c. IgG4-RD of the prostate gland, manifesting as a periprostatic mass-forming lesion in a 61-year-old man with flank pain. (a) Axial contrast-enhanced CT image at the midgland level shows bilateral enhancing lesions (solid arrows) surrounding the prostate gland (open arrows). (b–d) Consecutive transrectal US images of the prostate gland from the prostate base level (b) to the midgland level (c, d) show bilateral symmetric hypoechoic masslike lesions (solid arrows) surrounding the prostate gland (open arrows). Transrectal US image at the midgland level (d) shows the normal zonal anatomy of the central gland (CG) and peripheral zone (PZ). (e) Transrectal US-guided biopsy was performed through both periprostatic mass-forming lesions and the prostate tissue. (f) Photomicrograph shows a clear distinction (arrows) between the tissue from the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and the tissue from the prostate gland (p), with the normally preserved prostate gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g) Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT image shows ill-defined mildly enhancing soft-tissue infiltrative lesions (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both periprostatic lesions and peripelvic lesions regressed after steroid treatment (not shown).

IgG4-RD of the prostate gland, manifesting as a periprostatic                         mass-forming lesion in a 61-year-old man with flank pain. (a) Axial                         contrast-enhanced CT image at the midgland level shows bilateral enhancing                         lesions (solid arrows) surrounding the prostate gland (open arrows).                         (b–d) Consecutive transrectal US images of the prostate gland from                         the prostate base level (b) to the midgland level (c, d) show bilateral                         symmetric hypoechoic masslike lesions (solid arrows) surrounding the                         prostate gland (open arrows). Transrectal US image at the midgland level (d)                         shows the normal zonal anatomy of the central gland (CG) and peripheral zone                         (PZ). (e) Transrectal US-guided biopsy was performed through both                         periprostatic mass-forming lesions and the prostate tissue. (f)                         Photomicrograph shows a clear distinction (arrows) between the tissue from                         the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and                         the tissue from the prostate gland (p), with the normally preserved prostate                         gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g)                         Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid                         soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT                         image shows ill-defined mildly enhancing soft-tissue infiltrative lesions                         (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both                         periprostatic lesions and peripelvic lesions regressed after steroid                         treatment (not shown).

Figure 23d. IgG4-RD of the prostate gland, manifesting as a periprostatic mass-forming lesion in a 61-year-old man with flank pain. (a) Axial contrast-enhanced CT image at the midgland level shows bilateral enhancing lesions (solid arrows) surrounding the prostate gland (open arrows). (b–d) Consecutive transrectal US images of the prostate gland from the prostate base level (b) to the midgland level (c, d) show bilateral symmetric hypoechoic masslike lesions (solid arrows) surrounding the prostate gland (open arrows). Transrectal US image at the midgland level (d) shows the normal zonal anatomy of the central gland (CG) and peripheral zone (PZ). (e) Transrectal US-guided biopsy was performed through both periprostatic mass-forming lesions and the prostate tissue. (f) Photomicrograph shows a clear distinction (arrows) between the tissue from the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and the tissue from the prostate gland (p), with the normally preserved prostate gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g) Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT image shows ill-defined mildly enhancing soft-tissue infiltrative lesions (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both periprostatic lesions and peripelvic lesions regressed after steroid treatment (not shown).

IgG4-RD of the prostate gland, manifesting as a periprostatic                         mass-forming lesion in a 61-year-old man with flank pain. (a) Axial                         contrast-enhanced CT image at the midgland level shows bilateral enhancing                         lesions (solid arrows) surrounding the prostate gland (open arrows).                         (b–d) Consecutive transrectal US images of the prostate gland from                         the prostate base level (b) to the midgland level (c, d) show bilateral                         symmetric hypoechoic masslike lesions (solid arrows) surrounding the                         prostate gland (open arrows). Transrectal US image at the midgland level (d)                         shows the normal zonal anatomy of the central gland (CG) and peripheral zone                         (PZ). (e) Transrectal US-guided biopsy was performed through both                         periprostatic mass-forming lesions and the prostate tissue. (f)                         Photomicrograph shows a clear distinction (arrows) between the tissue from                         the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and                         the tissue from the prostate gland (p), with the normally preserved prostate                         gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g)                         Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid                         soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT                         image shows ill-defined mildly enhancing soft-tissue infiltrative lesions                         (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both                         periprostatic lesions and peripelvic lesions regressed after steroid                         treatment (not shown).

Figure 23e. IgG4-RD of the prostate gland, manifesting as a periprostatic mass-forming lesion in a 61-year-old man with flank pain. (a) Axial contrast-enhanced CT image at the midgland level shows bilateral enhancing lesions (solid arrows) surrounding the prostate gland (open arrows). (b–d) Consecutive transrectal US images of the prostate gland from the prostate base level (b) to the midgland level (c, d) show bilateral symmetric hypoechoic masslike lesions (solid arrows) surrounding the prostate gland (open arrows). Transrectal US image at the midgland level (d) shows the normal zonal anatomy of the central gland (CG) and peripheral zone (PZ). (e) Transrectal US-guided biopsy was performed through both periprostatic mass-forming lesions and the prostate tissue. (f) Photomicrograph shows a clear distinction (arrows) between the tissue from the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and the tissue from the prostate gland (p), with the normally preserved prostate gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g) Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT image shows ill-defined mildly enhancing soft-tissue infiltrative lesions (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both periprostatic lesions and peripelvic lesions regressed after steroid treatment (not shown).

IgG4-RD of the prostate gland, manifesting as a periprostatic                         mass-forming lesion in a 61-year-old man with flank pain. (a) Axial                         contrast-enhanced CT image at the midgland level shows bilateral enhancing                         lesions (solid arrows) surrounding the prostate gland (open arrows).                         (b–d) Consecutive transrectal US images of the prostate gland from                         the prostate base level (b) to the midgland level (c, d) show bilateral                         symmetric hypoechoic masslike lesions (solid arrows) surrounding the                         prostate gland (open arrows). Transrectal US image at the midgland level (d)                         shows the normal zonal anatomy of the central gland (CG) and peripheral zone                         (PZ). (e) Transrectal US-guided biopsy was performed through both                         periprostatic mass-forming lesions and the prostate tissue. (f)                         Photomicrograph shows a clear distinction (arrows) between the tissue from                         the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and                         the tissue from the prostate gland (p), with the normally preserved prostate                         gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g)                         Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid                         soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT                         image shows ill-defined mildly enhancing soft-tissue infiltrative lesions                         (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both                         periprostatic lesions and peripelvic lesions regressed after steroid                         treatment (not shown).

Figure 23f. IgG4-RD of the prostate gland, manifesting as a periprostatic mass-forming lesion in a 61-year-old man with flank pain. (a) Axial contrast-enhanced CT image at the midgland level shows bilateral enhancing lesions (solid arrows) surrounding the prostate gland (open arrows). (b–d) Consecutive transrectal US images of the prostate gland from the prostate base level (b) to the midgland level (c, d) show bilateral symmetric hypoechoic masslike lesions (solid arrows) surrounding the prostate gland (open arrows). Transrectal US image at the midgland level (d) shows the normal zonal anatomy of the central gland (CG) and peripheral zone (PZ). (e) Transrectal US-guided biopsy was performed through both periprostatic mass-forming lesions and the prostate tissue. (f) Photomicrograph shows a clear distinction (arrows) between the tissue from the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and the tissue from the prostate gland (p), with the normally preserved prostate gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g) Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT image shows ill-defined mildly enhancing soft-tissue infiltrative lesions (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both periprostatic lesions and peripelvic lesions regressed after steroid treatment (not shown).

IgG4-RD of the prostate gland, manifesting as a periprostatic                         mass-forming lesion in a 61-year-old man with flank pain. (a) Axial                         contrast-enhanced CT image at the midgland level shows bilateral enhancing                         lesions (solid arrows) surrounding the prostate gland (open arrows).                         (b–d) Consecutive transrectal US images of the prostate gland from                         the prostate base level (b) to the midgland level (c, d) show bilateral                         symmetric hypoechoic masslike lesions (solid arrows) surrounding the                         prostate gland (open arrows). Transrectal US image at the midgland level (d)                         shows the normal zonal anatomy of the central gland (CG) and peripheral zone                         (PZ). (e) Transrectal US-guided biopsy was performed through both                         periprostatic mass-forming lesions and the prostate tissue. (f)                         Photomicrograph shows a clear distinction (arrows) between the tissue from                         the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and                         the tissue from the prostate gland (p), with the normally preserved prostate                         gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g)                         Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid                         soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT                         image shows ill-defined mildly enhancing soft-tissue infiltrative lesions                         (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both                         periprostatic lesions and peripelvic lesions regressed after steroid                         treatment (not shown).

Figure 23g. IgG4-RD of the prostate gland, manifesting as a periprostatic mass-forming lesion in a 61-year-old man with flank pain. (a) Axial contrast-enhanced CT image at the midgland level shows bilateral enhancing lesions (solid arrows) surrounding the prostate gland (open arrows). (b–d) Consecutive transrectal US images of the prostate gland from the prostate base level (b) to the midgland level (c, d) show bilateral symmetric hypoechoic masslike lesions (solid arrows) surrounding the prostate gland (open arrows). Transrectal US image at the midgland level (d) shows the normal zonal anatomy of the central gland (CG) and peripheral zone (PZ). (e) Transrectal US-guided biopsy was performed through both periprostatic mass-forming lesions and the prostate tissue. (f) Photomicrograph shows a clear distinction (arrows) between the tissue from the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and the tissue from the prostate gland (p), with the normally preserved prostate gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g) Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT image shows ill-defined mildly enhancing soft-tissue infiltrative lesions (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both periprostatic lesions and peripelvic lesions regressed after steroid treatment (not shown).

IgG4-RD of the prostate gland, manifesting as a periprostatic                         mass-forming lesion in a 61-year-old man with flank pain. (a) Axial                         contrast-enhanced CT image at the midgland level shows bilateral enhancing                         lesions (solid arrows) surrounding the prostate gland (open arrows).                         (b–d) Consecutive transrectal US images of the prostate gland from                         the prostate base level (b) to the midgland level (c, d) show bilateral                         symmetric hypoechoic masslike lesions (solid arrows) surrounding the                         prostate gland (open arrows). Transrectal US image at the midgland level (d)                         shows the normal zonal anatomy of the central gland (CG) and peripheral zone                         (PZ). (e) Transrectal US-guided biopsy was performed through both                         periprostatic mass-forming lesions and the prostate tissue. (f)                         Photomicrograph shows a clear distinction (arrows) between the tissue from                         the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and                         the tissue from the prostate gland (p), with the normally preserved prostate                         gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g)                         Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid                         soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT                         image shows ill-defined mildly enhancing soft-tissue infiltrative lesions                         (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both                         periprostatic lesions and peripelvic lesions regressed after steroid                         treatment (not shown).

Figure 23h. IgG4-RD of the prostate gland, manifesting as a periprostatic mass-forming lesion in a 61-year-old man with flank pain. (a) Axial contrast-enhanced CT image at the midgland level shows bilateral enhancing lesions (solid arrows) surrounding the prostate gland (open arrows). (b–d) Consecutive transrectal US images of the prostate gland from the prostate base level (b) to the midgland level (c, d) show bilateral symmetric hypoechoic masslike lesions (solid arrows) surrounding the prostate gland (open arrows). Transrectal US image at the midgland level (d) shows the normal zonal anatomy of the central gland (CG) and peripheral zone (PZ). (e) Transrectal US-guided biopsy was performed through both periprostatic mass-forming lesions and the prostate tissue. (f) Photomicrograph shows a clear distinction (arrows) between the tissue from the periprostatic mass (m), with dense lymphoplasmacytic infiltration, and the tissue from the prostate gland (p), with the normally preserved prostate gland. (Hematoxylin-eosin stain; original magnification, ×40.) (g) Axial FDG PET/CT image at the same level as a shows bilateral FDG-avid soft-tissue lesions (arrows). (h) Axial contrast-enhanced excretory phase CT image shows ill-defined mildly enhancing soft-tissue infiltrative lesions (arrows) encasing the bilateral renal pelvis, without hydronephrosis. Both periprostatic lesions and peripelvic lesions regressed after steroid treatment (not shown).

IgG4-RD of the Testes

Testicular involvement in IgG4-RD can occur as a paratesticular fibrous pseudotumor or an epididymo-orchitis (60). A paratesticular fibrous pseudotumor is a rare benign tumorlike lesion and usually involves the tunica vaginalis, tunica albuginea, and epididymis, which results in diffuse or nodular thickening of the affected sites (64). Studies (6466) have shown that a paratesticular fibrous pseudotumor belongs to the list of IgG4-RDs on the basis of histopathologic and immunohistochemical findings. At T2-weighted MRI, a paratesticular fibrous pseudotumor shows low signal intensity with variable contrast enhancement (64,66). de Buy Wenniger et al (67) reported a case of testicular involvement of IgG4-RD in a 57-year-old man with multiorgan IgG4-RD. This patient initially presented with IgG4-RD autoimmune pancreatitis and later developed orchitis. In this patient, US images showed inhomogeneous echogenicity of the testis that mimics testicular malignancy or abscess-forming inflammation. In another case, Lal et al (68) reported a 1-cm hypoechoic nodule in the testis at US that was confirmed to be an isolated testicular involvement of IgG4-RD. Both patients with testicular IgG4-RD underwent orchiectomy because of suspicion for malignancy.

IgG4-RD of the Female Reproductive Organs

There are only a few case reports regarding the imaging manifestations of IgG4-RD involving the female reproductive organs. A case report (69) of IgG4-RD involving the uterus showed diffuse uterine enlargement, with heterogeneous enhancement at CT and diffuse radiotracer activity in the uterus, pleura, and periaortic area at FDG PET/CT in a 68-year-old woman with dyspnea but no gynecologic symptoms. For ovarian involvement, a large multinodular solid ovarian mass with iliac lymph node enlargement mimicking ovarian cancer was reported (70) in a 59-year-old woman with urinary retention. For uterine cervical involvement, a case of IgG4-RD involving the cervix as well as multiple organs including the pancreas, parotid glands, bilateral kidneys, and retroperitoneal lymph nodes was reported (71) in a patient with pathologically confirmed invasive cervical carcinoma. Although rare, the female reproductive organs are not excepted from IgG4-RD involvement.

Conclusion

IgG4-RD can involve almost every organ in the genitourinary system. Of these, the kidneys are the most frequently involved organs.

Teaching Point IgG4-RD involving the kidneys, ureter, bladder, urethra, prostate, testes, and female reproductive organs can show a broad spectrum of imaging findings, such as a localized mass in or surrounding the involved organ or diffuse enlargement of the involved organ, which may mimic a variety of both benign and malignant diseases (Table 2).
The diagnosis of IgG4-RD is based on a combination of clinical history, imaging findings, serologic markers, and characteristic histopathologic features. Although imaging findings are nonspecific for genitourinary system involvement of IgG4-RD, imaging has a key role in the detection of disease and monitoring of treatment response. Therefore, radiologists should be aware of variable imaging manifestations, clinicopathologic features, and differential diagnosis from mimics of IgG4-RD for accurate diagnosis to avoid unnecessary surgery and provide timely effective treatment.

Table 2: Imaging Manifestations of IgG4-RDs of the Genitourinary Organs and Main Differential Considerations

Table 2:
Disclosures of Conflicts of Interest.—J.C. Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: grants/grants pending from Bracco Korea and payments for lectures and travel from Bayer Korea. Other activities: disclosed no relevant relationships.

Recipient of a Cum Laude award for an education exhibit at the 2019 RSNA Annual Meeting.

For this journal-based SA-CME activity, the author J.C. has provided disclosures; all other authors, the editor, and the reviewers have disclosed no relevant relationships.

References

  • 1. Stone JH, Zen Y, Deshpande V. IgG4-related disease. N Engl J Med 2012;366(6):539–551. Crossref, MedlineGoogle Scholar
  • 2. Yoshida K, Toki F, Takeuchi T, Watanabe S, Shiratori K, Hayashi N. Chronic pancreatitis caused by an autoimmune abnormality. Proposal of the concept of autoimmune pancreatitis. Dig Dis Sci 1995;40(7):1561–1568. Crossref, MedlineGoogle Scholar
  • 3. Kamisawa T, Funata N, Hayashi Y, et al. A new clinicopathological entity of IgG4-related autoimmune disease. J Gastroenterol 2003;38(10):982–984. Crossref, MedlineGoogle Scholar
  • 4. Vlachou PA, Khalili K, Jang HJ, Fischer S, Hirschfield GM, Kim TK. IgG4-related sclerosing disease: autoimmune pancreatitis and extrapancreatic manifestations. RadioGraphics 2011;31(5):1379–1402. LinkGoogle Scholar
  • 5. Kamisawa T, Zen Y, Pillai S, Stone JH. IgG4-related disease. Lancet 2015;385(9976):1460–1471. Crossref, MedlineGoogle Scholar
  • 6. Bianchi D. IgG4-related disease: what urologists should know. Int Urol Nephrol 2016;48(3):301–312. Crossref, MedlineGoogle Scholar
  • 7. Obiorah IE, Henao Velasquez A, Özdemirli M. The Clinicopathologic Spectrum of IgG4-Related Disease. Balkan Med J 2018;35(4):292–300. Crossref, MedlineGoogle Scholar
  • 8. Bledsoe JR, Della-Torre E, Rovati L, Deshpande V. IgG4-related disease: review of the histopathologic features, differential diagnosis, and therapeutic approach. APMIS 2018;126(6):459–476. Crossref, MedlineGoogle Scholar
  • 9. Montironi R, Scarpelli M, Cheng L, et al. Immunoglobulin G4-related disease in genitourinary organs: an emerging fibroinflammatory entity often misdiagnosed preoperatively as cancer. Eur Urol 2013;64(6):865–872 [Published correction appears in Eur Urol 2015;67(4):e85.]. Crossref, MedlineGoogle Scholar
  • 10. Yamamoto M, Takahashi H. IgG4-Related Disease in Organs Other than the Hepatobiliary-Pancreatic System. Semin Liver Dis 2016;36(3):274–282. Crossref, MedlineGoogle Scholar
  • 11. Weindorf SC, Frederiksen JK. IgG4-Related Disease: A Reminder for Practicing Pathologists. Arch Pathol Lab Med 2017;141(11):1476–1483. Crossref, MedlineGoogle Scholar
  • 12. Geoghegan T, Byrne AT, Benfayed W, McAuley G, Torreggiani WC. Imaging and intervention of retroperitoneal fibrosis. Australas Radiol 2007;51(1):26–34. Crossref, MedlineGoogle Scholar
  • 13. Okazaki K. Autoimmune Pancreatitis and IgG4-Related Disease: The Storiform Discovery to Treatment. Dig Dis Sci 2019;64(9):2385–2394. Crossref, MedlineGoogle Scholar
  • 14. Zaheer A, Singh VK, Akshintala VS, et al. Differentiating autoimmune pancreatitis from pancreatic adenocarcinoma using dual-phase computed tomography. J Comput Assist Tomogr 2014;38(1):146–152. MedlineGoogle Scholar
  • 15. Katabathina VS, Khalil S, Shin S, Lath N, Menias CO, Prasad SR. Immunoglobulin G4-Related Disease: Recent Advances in Pathogenesis and Imaging Findings. Radiol Clin North Am 2016;54(3):535–551. Crossref, MedlineGoogle Scholar
  • 16. Kawano M, Saeki T. IgG4-related kidney disease--an update. Curr Opin Nephrol Hypertens 2015;24(2):193–201. Crossref, MedlineGoogle Scholar
  • 17. Wallace ZS, Naden RP, Chari S, et al. The 2019 American College of Rheumatology/European League Against Rheumatism classification criteria for IgG4-related disease. Ann Rheum Dis 2020;79(1):77–87. Crossref, MedlineGoogle Scholar
  • 18. Deshpande V, Zen Y, Chan JK, et al. Consensus statement on the pathology of IgG4-related disease. Mod Pathol 2012;25(9):1181–1192. Crossref, MedlineGoogle Scholar
  • 19. Kamisawa T, Shimosegawa T, Okazaki K, et al. Standard steroid treatment for autoimmune pancreatitis. Gut 2009;58(11):1504–1507. Crossref, MedlineGoogle Scholar
  • 20. Shimosegawa T, Chari ST, Frulloni L, et al. International consensus diagnostic criteria for autoimmune pancreatitis: guidelines of the International Association of Pancreatology. Pancreas 2011;40(3):352–358. Crossref, MedlineGoogle Scholar
  • 21. Opriţă R, Opriţă B, Berceanu D, Diaconescu IB. Overview of IgG4 - Related Disease. J Med Life 2017;10(4): 203–207. MedlineGoogle Scholar
  • 22. Takahashi N, Kawashima A, Fletcher JG, Chari ST. Renal involvement in patients with autoimmune pancreatitis: CT and MR imaging findings. Radiology 2007;242(3):791–801. LinkGoogle Scholar
  • 23. Seo N, Kim JH, Byun JH, Lee SS, Kim HJ, Lee MG. Immunoglobulin G4-Related Kidney Disease: A Comprehensive Pictorial Review of the Imaging Spectrum, Mimickers, and Clinicopathological Characteristics. Korean J Radiol 2015;16(5):1056–1067. Crossref, MedlineGoogle Scholar
  • 24. Kawano M, Saeki T, Nakashima H, et al. Proposal for diagnostic criteria for IgG4-related kidney disease. Clin Exp Nephrol 2011;15(5):615–626. Crossref, MedlineGoogle Scholar
  • 25. Zheng K, Teng F, Li XM. Immunoglobulin G4-related kidney disease: Pathogenesis, diagnosis, and treatment. Chronic Dis Transl Med 2017;3(3):138–147. Crossref, MedlineGoogle Scholar
  • 26. Salvadori M, Tsalouchos A. Immunoglobulin G4-related kidney diseases: An updated review. World J Nephrol 2018;7(1):29–40. Crossref, MedlineGoogle Scholar
  • 27. Saeki T, Nishi S, Imai N, et al. Clinicopathological characteristics of patients with IgG4-related tubulointerstitial nephritis. Kidney Int 2010;78(10):1016–1023. Crossref, MedlineGoogle Scholar
  • 28. Triantopoulou C, Malachias G, Maniatis P, Anastopoulos J, Siafas I, Papailiou J. Renal lesions associated with autoimmune pancreatitis: CT findings. Acta Radiol 2010;51(6):702–707. Crossref, MedlineGoogle Scholar
  • 29. Kim B, Kim JH, Byun JH, et al. IgG4-related kidney disease: MRI findings with emphasis on the usefulness of diffusion-weighted imaging. Eur J Radiol 2014;83(7):1057–1062. Crossref, MedlineGoogle Scholar
  • 30. Cortazar FB, Stone JH. IgG4-related disease and the kidney. Nat Rev Nephrol 2015;11(10):599–609. Crossref, MedlineGoogle Scholar
  • 31. Sheth S, Ali S, Fishman E. Imaging of renal lymphoma: patterns of disease with pathologic correlation. RadioGraphics 2006;26(4):1151–1168. LinkGoogle Scholar
  • 32. Ballard DH, De Alba L, Migliaro M, Previgliano CH, Sangster GP. CT imaging spectrum of infiltrative renal diseases. Abdom Radiol (NY) 2017;42(11):2700–2709. Crossref, MedlineGoogle Scholar
  • 33. Wagle DG, Moore RH, Murphy GP. Secondary carcinomas of the kidney. J Urol 1975;114(1):30–32. Crossref, MedlineGoogle Scholar
  • 34. Palmucci S, Torrisi SE, Caltabiano DC, et al. Clinical and radiological features of extra-pulmonary sarcoidosis: a pictorial essay. Insights Imaging 2016;7(4):571–587. Crossref, MedlineGoogle Scholar
  • 35. Lee YJ, Cho S, Kim SR. Unilateral and bilateral acute pyelonephritis: differences in clinical presentation, progress and outcome. Postgrad Med J 2014;90(1060):80–85. Crossref, MedlineGoogle Scholar
  • 36. Suzer O, Shirkhoda A, Jafri SZ, Madrazo BL, Bis KG, Mastromatteo JF. CT features of renal infarction. Eur J Radiol 2002;44(1):59–64. Crossref, MedlineGoogle Scholar
  • 37. Pickhardt PJ, Lonergan GJ, Davis CJ Jr, Kashitani N, Wagner BJ. From the archives of the AFIP. Infiltrative renal lesions: radiologic-pathologic correlation. Armed Forces Institute of Pathology. RadioGraphics 2000;20(1):215–243. LinkGoogle Scholar
  • 38. Yoshino T, Moriyama H, Fukushima M, Sanda N. A case of IgG4-related retroperitoneal fibrosis mimicking renal pelvic cancer. Urol Int 2013;90(3):365–368. Crossref, MedlineGoogle Scholar
  • 39. Kamo M, Nozaki T, Muraishi N, et al. CT Findings of Upper Urinary Tract Lesions in IgG4-Related Disease: Comparison With Urothelial Carcinoma. AJR Am J Roentgenol 2020. 10.2214/AJR.19.22192. Published online May 6, 2020. Crossref, MedlineGoogle Scholar
  • 40. Surabhi VR, Menias C, Prasad SR, Patel AH, Nagar A, Dalrymple NC. Neoplastic and non-neoplastic proliferative disorders of the perirenal space: cross-sectional imaging findings. RadioGraphics 2008;28(4):1005–1017. LinkGoogle Scholar
  • 41. Bechtold RE, Dyer RB, Zagoria RJ, Chen MY. The perirenal space: relationship of pathologic processes to normal retroperitoneal anatomy. RadioGraphics 1996;16(4):841–854. LinkGoogle Scholar
  • 42. Saeki T, Kawano M, Mizushima I, et al. The clinical course of patients with IgG4-related kidney disease. Kidney Int 2013;84(4):826–833. Crossref, MedlineGoogle Scholar
  • 43. Kawano M, Saeki T, Nakashima H. IgG4-related kidney disease and retroperitoneal fibrosis: An update. Mod Rheumatol 2019;29(2):231–239. Crossref, MedlineGoogle Scholar
  • 44. Zhong W, Kam J, Beattie K, Yuminaga Y, Ferguson R, Ko R. A Rare Case of Ureteral IgG4 Disease Masquerading as Urothelial Carcinoma. Urology 2018;118:e1–e2. Crossref, MedlineGoogle Scholar
  • 45. Marando A, D’Ambrosio G, Catanzaro F, La Rosa S, Sessa F. IgG4-related disease of the ureter: report of two cases and review of the literature. Virchows Arch 2013;462(6):673–678. Crossref, MedlineGoogle Scholar
  • 46. Kim SA, Lee SR, Huh J, Shen SS, Ro JY. IgG4-associated inflammatory pseudotumor of ureter: clinicopathologic and immunohistochemical study of 3 cases. Hum Pathol 2011;42(8):1178–1184. Crossref, MedlineGoogle Scholar
  • 47. Moriarty MA, Dahmoush L, Nepple KG. IgG4 related disease of the ureter (inflammatory pseudotumor). J Urol 2014;191(4):1126–1127. Crossref, MedlineGoogle Scholar
  • 48. Abe H, Morikawa T, Araki A, et al. IgG4-related periureteral fibrosis presenting as a unilateral ureteral mass. Pathol Res Pract 2011;207(11):712–714. Crossref, MedlineGoogle Scholar
  • 49. Lei WH, Xin J, Shao CX, et al. IgG4-related Kidney Disease Mimicking Malignant Ureter Tumor: Case Report and Literature Review. Medicine (Baltimore) 2016;95(3):e2550. Crossref, MedlineGoogle Scholar
  • 50. Takao A, Saika T, Uehara S, et al. Indications for ureteropyeloscopy based on radiographic findings and urine cytology in detection of upper urinary tract carcinoma. Jpn J Clin Oncol 2010;40(11):1087–1091. Crossref, MedlineGoogle Scholar
  • 51. Vaglio A, Maritati F. Idiopathic Retroperitoneal Fibrosis. J Am Soc Nephrol 2016;27(7):1880–1889. Crossref, MedlineGoogle Scholar
  • 52. Rossi GM, Rocco R, Accorsi Buttini E, Marvisi C, Vaglio A. Idiopathic retroperitoneal fibrosis and its overlap with IgG4-related disease. Intern Emerg Med 2017;12(3):287–299. Crossref, MedlineGoogle Scholar
  • 53. Vaglio A, Salvarani C, Buzio C. Retroperitoneal fibrosis. Lancet 2006;367(9506):241–251. Crossref, MedlineGoogle Scholar
  • 54. Caiafa RO, Vinuesa AS, Izquierdo RS, Brufau BP, Ayuso Colella JR, Molina CN. Retroperitoneal fibrosis: role of imaging in diagnosis and follow-up. RadioGraphics 2013;33(2):535–552. LinkGoogle Scholar
  • 55. Park S, Ro JY, Lee DH, Choi SY, Koo H. Immunoglobulin G4-associated inflammatory pseudotumor of urinary bladder: a case report. Ann Diagn Pathol 2013;17(6): 540–543. Crossref, MedlineGoogle Scholar
  • 56. Dropkin BM, Ingimarsson JP, Jones JD, Pettus JR, Seigne JD. Immunoglobulin G4-related disease in the urinary bladder. Int J Urol 2015;22(6):605–607. Crossref, MedlineGoogle Scholar
  • 57. Kufukihara R, Niwa N, Mizuno R, et al. Immunoglobulin G4-Related Disease Arising from the Bladder Wall. Urol Int 2019;103(4):488–490. Crossref, MedlineGoogle Scholar
  • 58. Gehring C, Starkebaum GA, Voelzke BB, Liew JW. Immunoglobulin G4-related disease of the urinary bladder. Rheumatology (Oxford) 2020;59(4):907–908. Crossref, MedlineGoogle Scholar
  • 59. Sangsoad P, Ramart P, Korpraphong P, Rerkpichaisuth V, Pradniwat K, Treetipsatit J. Female urinary retention from a huge periurethral mass caused by immunoglobulin G4-related disease (IgG4-RD). Urol Case Rep 2019;24:100844. Crossref, MedlineGoogle Scholar
  • 60. Brito-Zerón P, Ramos-Casals M, Bosch X, Stone JH. The clinical spectrum of IgG4-related disease. Autoimmun Rev 2014;13(12):1203–1210. Crossref, MedlineGoogle Scholar
  • 61. Buijs J, Maillette de Buy Wenniger L, van Leenders G, et al. Immunoglobulin G4-related prostatitis: a case-control study focusing on clinical and pathologic characteristics. Urology 2014;83(3):521–526. Crossref, MedlineGoogle Scholar
  • 62. Medlicott SAC, Oryschak A, Trpkov K. IgG4 prostatitis associated with prostatic adenocarcinoma: A case report and literature review. Hum Pathol Case Rep 2018;14:8–11. CrossrefGoogle Scholar
  • 63. Bourlon MT, Sánchez-Ávila M, Chablé-Montero F, Arceo-Olaiz R. IgG4-Related Autoimmune Prostatitis: Is It an Unusual or Underdiagnosed Manifestation of IgG4-Related Disease? Case Rep Urol 2013;2013:295472. MedlineGoogle Scholar
  • 64. ChangChien YC, Kovács I, Hargitai Z, Magyar L. Paratesticular Fibrous Pseudotumor: A New Entity of IgG4-Related Disease? Ann Clin Lab Sci 2018;48(3):381–385. MedlineGoogle Scholar
  • 65. Bösmüller H, von Weyhern CH, Adam P, Alibegovic V, Mikuz G, Fend F. Paratesticular fibrous pseudotumor--an IgG4-related disorder? Virchows Arch 2011;458(1): 109–113. Crossref, MedlineGoogle Scholar
  • 66. Kim KH, Sung DJ, Han NY, et al. Immunoglobulin G4-related paratesticular fibrous pseudotumor and retroperitoneal fibrosis: a case report. Urol Int 2015;94(3):369–372. Crossref, MedlineGoogle Scholar
  • 67. de Buy Wenniger LM, Scheltema JM, Verheij J, Beuers U. Testicular inflammation as a new manifestation of IgG4-associated disease. Urology 2013;82(2):e15–e16. Crossref, MedlineGoogle Scholar
  • 68. Lal J, Bhat S, Doddamani S, Devi L. Isolated testicular immunoglobulin G4-related disease: A mimicker of malignancy. Indian J Urol 2016;32(4):326–328. Crossref, MedlineGoogle Scholar
  • 69. Ohkubo H, Miyazaki M, Oguri T, Arakawa A, Kobashi Y, Niimi A. A rare case of IgG4-related disease involving the uterus. Rheumatology (Oxford) 2015;54(6):1124–1125. Crossref, MedlineGoogle Scholar
  • 70. Maruyama S, Sato Y, Taga A, Emoto I, Shirase T, Haga H. Immunoglobulin G4-related disease presenting as bilateral ovarian masses and mimicking advanced ovarian cancer. J Obstet Gynaecol Res 2016;42(1):103–108. Crossref, MedlineGoogle Scholar
  • 71. Mizuno R, Yamanishi Y, Uda S, Terashima T, Higashi T, Higuchi T. Invasive cervical cancer accompanied by IgG4-related disease. J Obstet Gynaecol Res 2016;42(9):1198–1202. Crossref, MedlineGoogle Scholar

Article History

Received: Mar 18 2020
Revision requested: Apr 21 2020
Revision received: June 15 2020
Accepted: June 19 2020
Published online: Sept 01 2020
Published in print: Sept 2020