Abstract
Emphysematous cystitis is a rare form of infection. Well known symptoms are: dysuria, urinary frequency and lower abdominal pain. We experienced a case of emphysematous cystitis presented with atypical peritoneal sign and computed tomography findings of massive intra-peritoneal fluid collection and abnormal gas appearance in pelvic space. Due to its presentation as acute abdomen, patient underwent exploratory laparotomy and the diagnosis of emphysematous cystitis was established. As far as we know, our case is the first report of emphysematous cystitis with intra-peritoneal fluid collection.