Genitourinary tract gas: imaging evaluation.

Gas-forming infections of the genitourinary tract may manifest as life-threatening conditions, often requiring aggressive medical and surgical management. Accurate interpretation of the radiologic studies is essential for early and accurate diagnosis of gas within the renal parenchyma or collecting system, bladder, uterus, and scrotum. Three distinct entities are associated with renal or perirenal gas: emphysematous pyelonephritis, emphysematous pyelitis, and gas-forming perirenal abscess. Gas in the bladder may occur secondary to emphysematous cystitis or a vesicoenteric fistula and must be differentiated from air introduced by means of instrumentation. Uterine gas usually indicates an underlying infection or a neoplasm. Gas in the scrotum is most commonly due to an infectious process or bowel herniation into the scrotal sac. Before institution of a specific therapeutic regimen, an effort should be made to establish the exact location of gas in the genitourinary tract. Plain radiography, including tomography, and ultrasonography are useful screening modalities. Although in some cases urography, barium enema studies, and other contrast material-enhanced studies enable a diagnosis to be made, in many patients computed tomography is the definitive diagnostic technique.