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Gastrointestinal Imaging

E2718. CT Signs of Internal Hernia Following Roux-en-Y Gastric Bypass With Surgical Correlation

Ngo S1,  Coakley K1,  McGettigan M2,  Harter E.1 1. Southern Illinois University School of Medicine, Springfield, IL; 2. University of South Florida College of Medicine/Moffitt Cancer Center, Tampa, FL

Address correspondence to S. Ngo (sngo@siumed.edu)

Objective: Internal hernia can lead to bowel ischemia and necrosis, so it is important for radiologists to recognize findings of internal hernia on CT studies. A variety of CT findings have been described, but sensitivity and specificity for many of these signs are relatively low. Thus, the diagnosis can be overlooked, even by experienced radiologists. We want to evaluate CT signs of internal hernia in our own cohort of patients.

Materials and Methods: We performed a retrospective study by reviewing 50 CT scans of individuals who had Roux-en-Y gastric bypass (RYGB) surgery from 2004–2013 and returned to surgery at Memorial Medical Center Bariatric Services from 2009–2014 for suspected internal hernia. All individuals were confirmed to have internal hernias at surgery. The CT scans were first reviewed individually and subsequently by consensus. Ten CT findings of internal hernia following RYGB were evaluated: mesenteric swirl, tubular mesentery, mushroom-shaped mesentery, clustered bowel loops, small bowel obstruction, small bowel displaced too high in the left upper quadrant, small bowel peripheral to colon or colon located centrally, distal jejunojejunal anastomosis located right of midline, change in location of the distal jejunojejunal anastomosis (if applicable), and interrupted superior mesenteric vein (SMV). Mesenteric swirl and interrupted SMV were also correlated to mesenteric edema. We examined the presence of each sign and agreement before and after consensus regarding the presence of each sign.

Results: The three most common CT signs were mesenteric swirl, small bowel peripheral to colon or colon located centrally, and interrupted SMV, which were present in 72% of cases of surgically proven internal hernias. The least common sign was small bowel obstruction, which was present in 12% of cases. Mesenteric edema was detected in 89% of cases in which mesenteric swirl was present. Mesenteric edema was also detected in 89% of cases in which interrupted SMV was present. The level of agreement among the three reviewers before consensus was greatest for the presence of interrupted SMV, change in location of the distal anastomosis, and distal anastomosis located right of midline, at 70%, 74%, and 84%, respectively. After consensus, the level of agreement was greatest for interrupted SMV and distal anastomosis located right of midline at 100%, and for mesenteric swirl and change in location of the distal anastomosis at 98%. Agreement before consensus was lowest for mushroom-shaped mesentery, clustered bowel loops, and tubular mesentery, at 24%, 28%, and 30%, respectively. The level of agreement after consensus remained lowest for those three signs as well, at 86%, 88%, and 86%, respectively.

Conclusion: Interrupted SMV is a frequent CT finding of internal hernia following RYGB with superior interobserver agreement. Internal hernia should not be excluded in the absence of small bowel obstruction.