The northern exposure sign: a newly described finding in sigmoid volvulus

OBJECTIVE. Previous studies of sigmoid volvulus have focused on the migrati on and dilatation of the sigmoid with respect to both fixed and mobile land marks in the abdomen. None has specifically referred to the relationship of this colonic segment to the more proximal large intestine. We analyzed fin dings on abdominal radiographs, all of which had been obtained with the pat ient supine, of sigmoid volvulus, with particular attention to the juxtapos ition of the sigmoid colon with the transverse colon. MATERIALS AND METHODS. The abdominal radiographs of 30 patients with clinic ally confirmed sigmoid volvulus were obtained from the teaching files of fo ur hospitals and were retrospectively reviewed. These radiographs were comp ared with abdominal radiographs of 28 individuals, each of whom had a dilat ed colon but not sigmoid volvulus. All radiographs bad been obtained with t he patient in the supine position. RESULTS. The transverse colon was identified in 26 of the 30 patients with sigmoid volvulus. In each of these 26 patients, the sigmoid colon was cepha lad to the transverse colon. Of the patients in the control group, the tran sverse colon was identified in 24 of the 28 patients. In none of these cont rol group patients did the sigmoid colon extend rostral to the transverse c olon. Thus, this sign had a sensitivity of 86% and a specificity of 100%. CONCLUSION. A dilated sigmoid colon that ascends cephalad to the transverse colon is a newly described and accurate finding of sigmoid volvulus on abd ominal radiographs obtained with the patient supine.