Radiological Features of the Spread and Localization of Extraperitoneal Gas and Their Relationship to Its Source

Extraperitoneal gas may be produced by (a) perforation of the descending duodenum, sigmoid diverticula, or rectum, (b) pancreatic or perirenal infection, or (c) extraperitoneal gas of subdiaphragmatic origin and displays a characteristic spread and localization depending upon its source. The author describes the anatomy of the extraperitoneal fascial planes and compartments and discusses the basic roentgen features of extraperitoneal gas and its distinction from intraperitoneal collections.