What is the main finding and what is the underlying cause?
Extensive pneumoperitoneum arising from a region of acute sigmoid diverticulitis.
What are some other causes of pneumoperitoneum?
Most cases of pneumoperitoneum are due to a perforated hollow viscus (e.g. peptic ulcer disease; ischaemic bowel; bowel obstruction; malignancy; mechanical perforation (e.g. trauma; colonoscopy; foreign bodies)). Gas may also be directly introduced into the abdominal cavity: iatrogenic (e.g. abdominal operations; peritoneal dialysis). High pressure mechanical ventilation can also result in extension of pneumomediastinum or pneumothorax into the peritoneal cavity.
What two incidental prior medical procedures are evident on this scan?
Intrauterine contraceptive device is present (IUCD) and the gallbladder is absent with clips indicative of prior cholecystectomy.
Diverticula throughout the colon. Focal fat stranding adjacent to a sigmoid diverticulum with a small amount of extraluminal fluid and gas locules. Significant amount of pneumoperitoneum. Appendix is normal in appearance. Previous cholecystectomy with associated intra- and extra-hepatic biliary duct dilatation. IUCD and IDC noted.