Pelvic Arterial Hemorrhage in Patients with Pelvic Fractures: Detection with Contrast-enhanced CT

LEARNING OBJECTIVES

After reading this article and taking the test, the reader will be able to:

Introduction

Pelvic fractures have been known to occur in 4%–9.3% of patients with blunt trauma (^,1,^,2). These fractures should be considered a marker of severe injury and are often associated with significant injuries to the abdominal and pelvic organs. The reported prevalence of associated organ injuries ranges from 11% to 20.3% (^,1).

Pelvic fractures have long been associated with significant mortality, which ranges from 5.6% to 15% (^,1–^,7). Recent studies, by well-organized trauma centers, have shown that the mortality rate is still high in patients who have hypotension attributable to pelvic fractures. The reported mortality rate for pelvic fracture patients with hemorrhagic shock ranges from 36.4% to 54% (^,7,^,8).

Life-threatening hemorrhage related to pelvic fractures may originate from fractured bone, the pelvic venous plexus, major pelvic veins, and/or iliac arterial branches. Pelvic fracture hemorrhage caused by venous injury and the fracture site can be effectively treated with external fixation by reducing the pelvic volume and stabilizing the fracture (^,9). Arterial hemorrhage is the most serious problem associated with pelvic fractures (^,5), and it remains the leading cause of death. Several authors have suggested that the external fixation is not likely to be sufficient to stop arterial bleeding. Urgent angiography and subsequent transcatheter embolization are currently accepted as the most effective methods for controlling ongoing arterial bleeding in pelvic fractures (^,3,^,5,^,10).

Patient death caused by the hemorrhage of a pelvic fracture frequently occurs within the first 24 hours of injury. The early identification of patients who might benefit from angiographic embolization could reduce blood loss, prevent late complications related to transfusion, and improve outcome (^,2). Several investigators have tried to define clinical or radiologic predictors to determine which patients with pelvic fractures are at high risk of arterial hemorrhage and thus might benefit from angiography and embolization. These predictors include the response to initial resuscitation (^,7), pelvic fracture pattern according to radiography results (^,8,^,11), the volume and location of pelvic hematoma according to the results of computed tomography (CT) (^,6,^,12), and the extravasation of injected contrast material according to the results of a contrast-enhanced CT examination (^,5,^,13–^,16). In patients with both hypotension and pelvic fracture, a lack of response to initial resuscitation and contrast material extravasation seen on a CT scan are the most reliable indicator of significant arterial bleeding regardless of the fracture pattern (^,7).

Several studies have shown that the presence of contrast material extravasation on contrast-enhanced CT scans is a strong predictor of arterial bleeding later seen during angiography (^,13–^,16). Moreover, the presence of contrast material extravasation can be an indicator of injury to a specific artery passing through the region of the pelvis where the extravasation is noted on CT scans. Interventional radiologists can use the location of contrast material extravasation on CT scans to direct the performance of more specific selective and superselective investigations of arteries at high risk for injury.

In this article, we describe the role of contrast-enhanced CT in predicting arterial hemorrhage in patients with pelvic fractures. The specific topics discussed are the relevant pelvic anatomy, the axial CT anatomy of the internal iliac artery and its branches, the correlation between findings of contrast-enhanced CT and those of angiography (relationship between a CT-determined extravasation site and an angiographically determined bleeding site), and transcatheter arterial embolization (TAE) in patients with arterial hemorrhage and pelvic fractures.

Essential Pelvic Anatomy

The internal iliac artery, which is also known as the hypogastric artery, begins at the bifurcation of the common iliac artery, anterior to the sacroiliac joint at the level of the lumbosacral disk. It supplies the walls of the pelvis, the pelvic viscera, the buttock, the genital organ, and part of the medial thigh. The internal iliac artery divides into an anterior and posterior trunk. The branches of the internal iliac artery may be grouped as follows: (a) Visceral branches: umbilical, superior vesical, inferior vesical, middle rectal, uterine, and vaginal. (b) Branches to the limb and perineum: superior gluteal, inferior gluteal, obturator, and internal pudendal. (c) Somatic segmental branches: iliolumbar and lateral sacral. Usually, the superior gluteal and the two somatic segmental branches stem from the posterior division and the others from the anterior division (^,Figs 1, ^,2).

The internal iliac artery and its branches have a close relationship with the pelvic ligaments and foramina throughout their course in the pelvis. Knowledge of the precise anatomy of pelvic bony and ligamentous structures is required to understand the mechanism of arterial injury in patients with acute pelvic trauma. The door through which all vessels and nerves pass on leaving the pelvis to enter the gluteal region is the greater sciatic foramen (^,Fig 3). It is bounded by the sacrum posteriorly, by the sacrospinous ligament inferiorly, by the ischium anteriorly, and by the ilium superiorly. The sacrospinous ligament attaches the lateral and inferior aspects of the sacrum to the ipsilateral ischial spine, and it forms the inferior border of the greater sciatic foramen below the greater sciatic notch of the hip bone. The piriformis muscle arises from the anterior sacrum and passes out of the pelvis through the greater sciatic foramen. Coursing laterally, this muscle inserts on the greater trochanter of the femur (^,Fig 4). The piriformis muscle separates the greater sciatic foramen into superior and inferior portions.

Superior gluteal vessels and nerves are located at the upper border of the piriformis muscle. Inferior gluteal vessels and nerves, internal pudendal vessels and nerves, and the sciatic nerve are located at the lower border of the piriformis muscle. Internal pudendal vessels and nerves leave the pelvis through the inferior part of the greater sciatic foramen and at once reenter through the lesser sciatic foramen (^,Figs 2, ^,4).

The lesser sciatic foramen is bounded by the ischial tuberosity anteriorly, by the ischial spine and sacrospinous ligament superiorly, and by the sacrotuberous ligament posteriorly (^,Fig 3). The sacrotuberous ligament attaches the lateral sacrum to the ipsilateral ischial tuberosity. The vertical band of this ligament extends up to the posterior superior spine of the ilium, where it blends with the vertical bands of the posterior sacroiliac ligament.

The obturator foramen is a large, rounded aperture that separates the pubis anterosuperiorly from the ischium posteroinferiorly. The fibrous obturator membrane completely covers the obturator foramen except superiorly, where a deep groove allows communication between the pelvis and the anterior thigh. Through this obturator canal, the obturator vessels and nerves exit the pelvis (^,Figs 2, ^,3).

It is essential to subsequently apply the described anatomy to axial CT images for the interpretation and prediction of arterial injury in patients with pelvic fracture hemorrhage. On arterial CT images from a multidetector CT scanner, the fine branches of the internal iliac artery can be easily traced from its origin through their courses in the pelvis.

Vascular Anatomy at Axial CT

The increasing use of contrast-enhanced CT in the evaluation and management of patients with pelvic fractures necessitates a greater knowledge of the relevant pelvic anatomy, including the bony, ligamentous, and especially axial vascular anatomy. Knowledge of axial CT vascular anatomy of the pelvis is essential for understanding the relationship between a contrast material extravasation site seen on a CT scan and the specific injured arteries seen during angiography. Contrast-enhanced CT studies performed with a multidetector scanner can provide a clear image of the branches of the internal iliac artery and their course in relation to the pelvic bony and ligamentous structures.

The iliolumbar artery is usually the first branch of the internal iliac artery, and it arises from the posterior division. It courses upward and laterally anterior to the sacroiliac joint and divides into a lumbar and an iliac branch just above the pelvic inlet and behind the psoas major muscle (^,Figs 5^,–^,7). The iliac branch of the iliolumbar artery runs laterally anterior to the iliacus muscle. It supplies the iliacus muscle, the gluteal and abdominal muscles, and the ilium. The iliolumbar artery is known to be the largest nutrient artery to the ilium. The lumbar branch of the iliolumbar artery ascends anterior to the sacral ala and lateral to the L5 body.

The lateral sacral arteries arise from the posterior trunk of the internal iliac artery; there are usually two arteries, a superior and an inferior. They supply branches to the anterior surface of the sacrum, the sacral foramina and sacral canal, and the skin and muscles of the dorsal surface of the sacrum (^,Figs 8^,–^,10). On CT scans, the lateral sacral arteries are seen to descend along the sacrum and divide into branches that enter the sacral foramina.

The superior gluteal artery is the largest branch of the internal iliac artery. It exits from the pelvis through the greater sciatic foramen, above the superior border of the piriformis muscle. On CT images, it is located posterior to the ilium and superior to the piriformis muscle at the greater sciatic foramen. After leaving the pelvis, it divides into superficial and deep branches, which are noted in the fat planes between gluteus muscles on CT scans (^,Figs 11^,–^,13).

The inferior gluteal artery leaves the pelvis together with the internal pudendal artery through the lower part of the greater sciatic foramen, between the piriformis muscle and the coccygeus muscle. It is distributed to the buttocks and back of the thigh and continues down the posterior thigh. On CT scans, the inferior gluteal artery is seen anterior to the piriformis muscle, posterior to the ischial spine, and above the sacrospinous ligament at the greater sciatic foramen. It travels down the posterior buttock and is covered by the gluteus maximus muscle after leaving the pelvis (^,Figs 14^,–^,16).

The internal pudendal artery emerges from the pelvis through the lower part of the greater sciatic foramen. It crosses behind the ischial spine and reenters the pelvis through the lesser sciatic foramen (^,Figs 17^,,,–^,21). On CT scans, the internal pudendal artery is easily identified posterior to the ischial spine and sacrospinous ligament after leaving the pelvis; it runs along the medial surface of the obturator internus muscle, which forms the lateral border of the ischiorectal fossa, after reentering the pelvis.

The obturator artery runs ventrally along the lateral wall of the pelvis to the obturator canal. It exits the pelvis through the obturator canal and divides into anterior and posterior branches at that point. The obturator artery supplies the muscles around the hip (^,Figs 22^,–^,24). On CT images, the artery runs along the anterior pelvic sidewall, medial to the upper portion of the obturator internus muscle, and it has a close relationship to the acetabulum. It is easily seen in the obturator canal as it divides into anterior and posterior branches.

It is not easy to identify the visceral branches of the internal iliac artery on CT images, except for the uterine artery. The uterine artery extends to the uterine cervix within the broad ligament and runs cephalad along the uterine body, anastomosing with the ovarian artery. On CT images, the uterine artery and its branches have a typical corkscrew appearance within the broad ligament. The superior vesical artery can be seen lateral to the bladder on CT images. The inferior vesical artery is rarely visualized on CT images (^,Figs 25, ^,26).

CT-Angiographic Correlation of Arterial Hemorrhage Related to Pelvic Fractures

Contrast-enhanced CT has been reported to be an accurate, noninvasive technique for identifying ongoing arterial hemorrhage in patients with pelvic fractures (^,13–^,16). The presence of the extravasation of contrast materials on contrast-enhanced CT scans is highly predictive of arterial injury that will require angiographic embolization (^,15) and has been found to be a reliable indicator of arterial hemorrhage, with a sensitivity of 66%–90%, a specificity of 85%–98%, and an accuracy of 87%–98% being reported (^,5,^,14–^,16). It is well known that extravasated contrast material can be distinguished from clotted blood by measuring CT attenuation. Shanmuganathan et al (^,13) reported that the CT attenuation of active contrast material extravasation ranged from 85 to 370 HU (mean, 132 HU), whereas clotted blood revealed a CT attenuation range of 40–70 HU (mean, 51 HU).

The detection of contrast material extravasation on CT scans facilitates timely, life-saving angiographic embolization. Furthermore, the site of contrast material extravasation seen on CT scans corresponds well to the site of bleeding seen during angiography in patients with pelvic fracture hemorrhage. Thus, it enables the interventional radiologist to selectively study the arteries that are most likely to be bleeding. This can lead to more rapid transcatheter embolization, which has the potential to reduce a patient’s morbidity and mortality.

Recently, the introduction of multidetector helical CT has markedly decreased the time required for scanning, and it has now become a diagnostic modality of choice in the evaluation of patients with pelvic fractures in many trauma centers, even in patients with some degree of hemodynamic instability.

Any posterior fracture line involving the ilium or anterior sacroiliac joint disruption, which occurs in anterior-posterior compression and shearing injuries, is liable to lead to serious hemorrhage from the iliolumbar artery for two reasons: The branch in the largest nutrient foramen of the ilium is invariably a branch of the iliolumbar artery (^,17), and the presence of the iliolumbar artery is in immediate proximity to the anterior sacroiliac joint. On CT images, contrast material extravasation located anterior to the sacroiliac joint that is associated with sacroiliac joint disruption or within the iliacus muscle hematoma with associated fractures of the ilium is highly suggestive of injury to the iliolumbar artery (^,,,Fig 27).

Posterior transsacral fractures or a fracture line involving the sacral foramina, through which the lateral sacral arteries exit the pelvis, is prone to cause injury of the lateral sacral arteries. The injury of the lateral sacral arteries is commonly associated with lateral compression pelvic fractures or vertical shear injury. On CT images, contrast material extravasation noted within the presacral hematoma associated with a fracture line that involves the sacral foramina is highly indicative of injury to the lateral sacral arteries (^,,,Fig 28).

The superior gluteal artery can be injured by the sharp fascia of the piriformis muscle as it exits the pelvis through the greater sciatic foramen above the piriformis muscle (^,,,Fig 29). Outside the pelvis, the superficial and deep branches of the superior gluteal artery can be traumatized when the gluteal muscles are severely contused, as in cases of anterior-posterior compression injury (^,9). The main branch of the inferior gluteal artery can be injured as it exits the pelvis just posterior and superior to the midportion of the sacrospinous ligament. Fracture lines involving the greater sciatic foramen, the superior part of the ischial tuberosity, and the ischial spine are prone to cause injury of both the superior and inferior gluteal arteries. On CT images, contrast material extravasation within the gluteal hematoma is indicative of an injury to the superior gluteal artery.

The internal pudendal artery can be traumatized in anterior-posterior compression, the so-called “open-book” fracture, type II and III injury. Fractures of the inferior ramus of the pubic bone may be responsible for injury to the internal pudendal artery because of its close proximity to the ischiopubic ramus. Fractures that involve the lesser sciatic foramen can also lead to an injury of the internal pudendal artery. On CT images, contrast material extravasation seen in the region of the ischiorectal fossa or urogenital diaphragm fat plane that is associated with diastasis of the symphysis pubis or vertical fractures through the ischiopubic ramus is highly indicative of injury to the internal pudendal artery (^,,,Fig 30).

The branches of the anterior and posterior divisions of the obturator artery supply the superior part of the surroundings of the obturator foramen and the anteroinferior and posteroinferior parts of the acetabulum. Thus, fracture lines involving the superior part of the obturator foramen, the superior pubic ramus, or the pubic acetabulum are prone to cause injury to the obturator artery. On CT images, contrast material extravasation seen in the region of the pelvic sidewall or within an obturator internus muscle hematoma that is associated with fractures involving the superior pubic ramus or pubic acetabulum is highly suggestive of injury to the obturator artery (^,,,,,,Fig 31). Pelvic arterial bleeding due to injury of visceral branches in patients with pelvic fracture is quite rare. Extravasation of contrast material in the bladder wall can be seen on contrast-enhanced CT scans when the vesical arteries are injured (^,,,Fig 32).

Arterial extravasation of contrast materials must be distinguished from contrast material that may have leaked from the urinary tract (^,15). Retrograde urethrography or cystography should not be performed before contrast-enhanced CT and angiography in patients with pelvic fractures and hemorrhagic shock because leaked contrast material obscures the view of the arterial extravasation sites and therefore makes difficult the early diagnosis and treatment of such critically ill patients (^,18).

Transcatheter Arterial Embolization

Transcatheter arterial embolization (TAE) is now considered to be the treatment of choice in patients with arterial hemorrhage related to pelvic fractures (^,3,^,5,^,10,^,19). If a patient is hemodynamically unstable despite initial resuscitation, urgent arteriography and embolization are recommended. In patients who undergo contrast-enhanced CT, angiographic embolization should be performed to control potentially life-threatening arterial hemorrhage when contrast material extravasation is seen on CT scans.

The efficacy of TAE in the management of arterial hemorrhage caused by pelvic fractures has been demonstrated. The success rate, expressed in terms of hemorrhage control and reduction in transfusion requirement, ranges from 85% to 100% (^,3,^,10,^,19). TAE should be performed as early as possible, because effective embolization must be achieved before severe systemic coagulopathy and multiple organ failure develop (^,20). Agolini et al (^,3) reported that the mortality rate was 14% (1 of 7) in embolized patients who arrived in the angiography suite within 3 hours of their injury but was 75% (6 of 8) for patients who arrived after 3 hours. Eastridge et al (^,8) reported that the mortality rate was 25% (1 of 4) in patients with unstable pelvic fracture patterns who underwent TAE before celiotomy but was 60% (6 of 10) for patients who underwent celiotomy before TAE. They concluded that angiography should be considered an initial intervention in patients with unstable pelvic fractures, even in the presence of hemoperitoneum.

In addition, there are several issues that should be taken into account when performing TAE in patients with pelvic fracture hemorrhage. Even if no significant bleeding is seen on the aortogram, selective injection of the internal iliac arteries is necessary, because the bleeding may be intermittent and the characteristics of the arteries that may be injured are more evident (^,,,,,Fig 33). It is also important to selectively study the contralateral internal iliac artery to search for other potential bleeding sites and collateral flow that may contribute to the original bleeding site (^,19) (^,,,,,,Fig 31).

A capillary and venous phase blush in the region of the distal branches of the internal pudendal artery that simulates bleeding can sometimes be seen on arteriograms of male patients who are not bleeding (^,,,Fig 30b). This normal variation, which is called the “cavernosal blush,” is characterized by a bilaterally symmetric, homogeneous stain at the base of the penis that washes out, and it should not be confused with active hemorrhage (^,21).

In general, patients who need angiography tend to be older, require more transfusion before angiography, and have worse injury severity scores than those who do not (^,4,^,10). Thus, it is not surprising that the mortality rate is still high in patients who undergo angiographic embolization. The mortality rates among patients who undergo successful TAE have been reported to be 17.6%–47% (^,3,^,5,^,10).

Conclusions

Evidence of active extravasation of contrast materials on contrast-enhanced CT scans is highly suggestive of arterial bleeding in patients with pelvic fractures. Contrast-enhanced CT allows identification of contrast material extravasations in locations that are predictive of injuries to specific arterial branches of the internal iliac artery. Thus, CT can guide interventional radiologists in the selective angiographic investigation and embolization of specific injured arteries. This can lead to more rapid transcatheter embolization of bleeding arteries, which has the potential to reduce patient morbidity and mortality.

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Download as PowerPointOpen in Image Viewer

Abbreviation: TAE = transcatheter arterial embolization