Computed tomography findings of internal hernia after gastric bypass that may precede small bowel obstruction

This study evaluates computed tomography signs of internal hernia in gastric bypass patients, including several previously unreported signs suggestive of internal hernia. Eighteen patients with surgically proven internal hernia were included in the study cohort. The signs analyzed included the mesenteric swirl, hurricane eye, mushroom sign, and dilated small bowel loops, as well as previously non-investigated signs such as bowel wall edema, engorged mesenteric vessels, engorged mesenteric lymph nodes, and hazy mesenteric fat. We also separately examined internal hernia patients without overt small bowel obstruction (SBO), since these are the patients most likely to get overlooked by radiologists. The most prevalent sign in all internal hernia patients was mesenteric vessel engorgement, seen in approximately 79-84 % of patients overall and 73-75 % of patients without overt SBO. The level of agreement between our two readers for the eight total signs reviewed was all moderate to substantial (using Cohen kappa values), reflecting their reliability as markers of internal hernia. The highest level of agreement was seen in vessel engorgement at 0.91, followed by three other signs [hurricane eye, SBO, bowel edema] with levels of agreement at 0.86. We conclude that more subtle signs of internal hernia should be included in radiologist search patterns for patients with internal hernia, especially those presenting multiple times for abdominal pain, as these may reflect surgically correctable intermittent herniations.