Colonic volvulus is a relatively uncommon cause of large bowel obstruction usually involving mobile, intra-peritoneal, colonic segments. Congenital or acquired anatomic variation may be associated with an increased risk of colonic volvulus which can occasionally involve retro-peritoneal segments. We report a case of 54-year-old female who presented to our Institution to perform a plain abdominal film series for acute onset of cramping abdominal pain. Both the upright and supine films showed signs of acute colonic obstruction which was thought to be due to an internal hernia of the transverse colon into the lesser sac. The patient was therefore submitted to a multi-detector contrast-enhanced computed tomography (CT). CT findings were initially thought to be consistent with the presumed diagnosis of internal hernia but further evaluation and coronal reformatting clearly depicted the presence of a colonic volvulus possibly resulting from a retro-gastric colon. At surgery, a volvulus of the ascending colon was found and a right hemi-colectomy had to be performed. However, a non rotated midgut with a right-sided duodeno-jejunal flexure and a left sided colon was also found at laparotomy and overlooked in the pre-operative CT. Retrospective evaluation of CT images was therefore performed and a number of CT signs of intestinal malrotation could be identified.