Extraperitoneal gas: compartmental localization and identification of source.

We evaluated the plain films of the abdomen and chest in 24 patients with documented extraperitoneal gas collections. Compartmental localization of the extraperitoneal ectopic gas in these patients was as follows: the anterior pararenal space in 10 patients, the perirenal space in five and the posterior pararenal space in 15. In six of these 24 patients, the extraperitoneal gas was present in two compartments. The extraperitoneal gas collection resulted from perforation of the retroperitoneally located alimentary tract in 11, necrotizing pancreatitis in five, gas-producing infection in four and from extension of extra-alveolar air in three patients. Air insufflation of the scrotum was the cause of the extraperitoneal gas in another patient.