Sigmoid volvulus showing a "whirl sign" on computed tomography

Background Sigmoid volvulus is a rare condition. A high incidence has been reported in debilitated, or chronically constipated patients. It is important to recognize this condition early and then initiate prompt treatment. Endoscopic treatment has a high perforation risk. The "whirl sign", was first described by Fisher, as suggesting volvulus of the small bowel, and it was considered that this sign represents the superior mesenteric artery at the centre surrounded by bowel loops. In a patient with sigmoid volvulus, the whirl sign is caused by tightly twisted bowel and mesentery.