This 52 year old lady presented with sudden onset severe abdominal pain. CT abdomen shows a large amount of free fluid and free gas. There is thickening of the wall of the caecum and ascending colon.

Caecal perforation was found at laparotomy with faecal peritonitis. A right hemicolectomy was performed because of an abnormal appearance of the bowel. Pathological examination revealed a stenosing moderately differentiated adenocarcinoma of the right colon (Duke’s B), with proximal bowel dilatation and wall oedema.
Malignant bowel neoplasms are a recognized cause of bowel perforation. In this case perforation was probably due to obstruction and caecal dilatation. Other causes of pneumoperitoneum from bowel perforation are peptic ulcer, diverticulitis, appendicitis, toxic megacolon, necrotizing enterocolitis, bowel infarction and pneumatosis coli.

Chapman and Nakielny. Aids to radiological differential diagnosis. 4th edition. Saunders 2003.
Credit: Dr Bernard Ng