Sensitivity and specificity of eight CT signs in the preoperative diagnosis of internal mesenteric hernia following Roux-en-Y gastric bypass surgery

Abstract

To evaluate the sensitivity and specificity of eight previously reported computed tomography (CT) signs in diagnosing internal mesenteric hernia following Roux-en-Y gastric bypass surgery. Preoperative CT images of nine patients with surgically proven internal mesenteric hernia as a complication of gastric bypass surgery and 10 matched control patients were reviewed in a blinded fashion by three radiologists. The presence of eight previously reported signs of internal mesenteric hernia was assessed: mesenteric swirl sign, hurricane eye sign, mushroom sign, small bowel obstruction, clustered small bowel loops, small bowel other than duodenum located behind the superior mesenteric artery (SMA), presence of the jejunal anastomosis to the right of the midline, and engorged mesenteric lymph nodes. The sensitivity and specificity were calculated for each sign, as well as inter-observer reliability in recognizing these signs. Mesenteric swirl was the most predictive sign of internal hernia (sensitivity 78-100%, specificity 80-90%). Other CT signs showed good specificity (70-100%), but sensitivities were low (0-44%). The presence of a small-bowel obstruction and engorged mesenteric nodes was found to be 100% specific in predicting the presence of an underlying hernia. There was substantial inter-observer agreement in detecting mesenteric swirl sign (kappa=0.48-0.79), but agreement was relatively poor for all other signs. Mesenteric swirl is an easily recognized CT sign, and is the best indicator of internal hernia following Roux-en-Y gastric bypass surgery. Other reported CT signs are diagnostically insensitive. The presence of small-bowel obstruction with engorged mesenteric nodes is highly specific in diagnosing internal mesenteric hernia.