Emphysematous cystitis with extraperitoneal gas: new insights into pathogenesis via novel CT findings.

Emphysematous cystitis is a relatively rare disease entity characterized by intramural and/or intraluminal bladder gas best depicted by cross-sectional imaging. Its disease mechanism is not well understood. A case of a diabetic patient with emphysematous cystitis is presented and is notable for the rare finding of extraperitoneal gas in the pelvis based on a review of 114 case reports. Herein we propose a distension-based mechanism with intramural bacterial seeding as the pathogenesis of emphysematous cystitis based on the patient's imaging and the disease's established associations with diabetes and E. coli. The ability to recognize extraperitoneal pelvic gas as a feature of emphysematous cystitis allowed prompt diagnosis. This facilitated early commencement of successful treatment in a diabetic patient in whom the diagnosis was not suspected clinically.