Gas-forming bacterial peritonitis mimics hollow organ perforation.

Acute abdomen is an emergent condition in the emergency department, and it is mandatory to evaluate it immediately and treat it without delay. Pneumoperitoneum is usually attributed to perforation of the gastrointestinal tract. However, intra-abdominal, gynecologic, urologic, and miscellaneous pathogenesis not related to a perforated gastrointestinal tract had never been described in the past. Approximately 10% of pneumoperitoneum is not associated with hollow organ perforation. There are many imitators of pneumoperitoneum including subphrenic abscess, colon volvulus, Chilaiditi syndrome, and so on. In our case, the gas-forming bacterial peritonitis accounted for the pneumoperitoneum. We presented an 85-year-old man who received laparotomy due to peritonitis, and radiographic subphrenic free air was seen. However, a large amount of ascites was found rather than perforated bowels during the surgical exploration, and the culture of ascites was positive for Pseudomonas aeruginosa.