The patient whose images are illustrated below presented with a 4-day history of fluctuating lower abdominal pain. He had not had a bowel motion. A plain abdominal radiograph showed a hugely dilated loop of sigmoid colon assuming the shape of an inverted U. Haustra were not identified in the sigmoid loop and the two limbs of the loop converged inferiorly at the lower lumbar level. The proximal large bowel was dilated. A computed tomography scan of the abdomen was performed with 3D-multiplanar reformation (Figs 1 and 2). The images show a dilated loop of sigmoid colon, dilatation of the proximal large bowel and a prominent ‘whirl sign’ caused by torsion of the sigmoid mesentery. At flexible sigmoidoscopy, the twisting began at 30 cm from the anal margin. There were no endoscopic features of colonic ischemia and advancement of the endoscope resulted in decompression of the volvulus.

Patients with sigmoid volvulus are usually elderly (>70 years) and have a higher than expected frequency of institutional care because of psychiatric illness. Whether this is associated with chronic constipation remains unclear. Typical clinical features include fluctuating abdominal pain for 4–5 days, abdominal distension and only mild abdominal tenderness. Rare patients have perforation of the sigmoid colon and present with peritonitis. The optimal management of sigmoid volvulus is debated. In the absence of features of peritonitis, decompression of the volvulus can usually be achieved with a rigid sigmoidoscope and a soft rectal tube. Other options for decompression include air insufflation at colonoscopy and an enema X-ray using water-soluble contrast. Decompression rates for the latter procedures remain unclear and there is some risk of colonic perforation. The definitive treatment of sigmoid volvulus is resection of the sigmoid colon because patients treated by decompression procedures have a risk of recurrence of at least 40%.

  1. Contributions to the Images of Interest Section are welcomed and should be submitted to Professor IC Roberts-Thomson, Department of Gastroenterology, The Queen Elizabeth Hospital, Woodville South, South Australia 5011, Australia.