Internal Hernias after Roux-en-Y Gastric Bypass: Clues to a Challenging Diagnosis.

Roux-en-Y gastric bypass (RYGB) is a common and effective treatment of obesity. The development of an internal hernia after RYGB is the result of herniation of the small bowel through mesenteric defects created at the time of surgery. This can lead to further complications including recurrent abdominal pain and small bowel obstruction. In the most dire cases, closed-loop obstruction and/or volvulus can occur and lead to bowel ischemia and necrosis. Given the potentially severe complications of internal hernias after RYGB, it is incumbent on the radiologist to assess for them in all patients undergoing abdominal CT who have undergone RYGB, especially those presenting with abdominal pain. Detection of an internal hernia after RYGB at CT can be challenging. The authors discuss the postoperative anatomy after RYGB and the manner in which it can lead to internal hernias, the incidence of and risk factors for internal hernias, and the various signs at CT that can signal the presence of an internal hernia after RYGB. ©RSNA, 2025 Supplemental material is available for this article.