Visit casereports. bmj. com for more articles like this and to become a Fellow one large air-filled outpouching (11× 6 cm) anterior to the sigmoid colon (figure 2), which was initially (prior to a formal radiology report) thought to be a contained bowel perforation, although there was no evidence of any other pockets of free air in the abdominal cavity. After review of the images by a consultant radiologist, the CT was reported as a giant sigmoid diverticulum (figures 3 and 4) originating from the sigmoid colon, with inflammatory changes suggestive of acute diverticulitis. The patient was managed conservatively with intravenous fluids and antibiotics. contributors Initial idea by AM. AM and SL contributed to the first draft and acquisition of data. Consent was obtained by SL. AM and SL wrote and agreed on the final draft. competing interests None declared. patient consent Obtained. provenance and peer review Not commissioned; externally peer reviewed.