Background: Roux-en-Y gastric bypass (RYGB) is one of the most common bariatric procedures. Internal herniation may lead to small bowel ischemia requiring small bowel resection, resulting in short bowel syndrome.

Objective: To determine the incidence of extensive small bowel resection in patients operated with RYGB. We also aimed to look for early clinical warning signs among patients requiring extensive small bowel resection.

Setting: Cohort from national quality registers.

Methods: All patients having undergone RYGB between January 2007 to June 2019 were analyzed in the Scandinavian Obesity Surgery Registry (SOReg). We identified patients with small bowel obstruction (SBO) for whom small bowel resection was necessary. Additionally, we assessed clinical signs in these patients.

Results: The study included 57,255 patients having undergone RYGB. Closure of the mesenteric openings was performed in 78%. Surgery for SBO was required in 3659 (6%) of patients, and small bowel resection in 188 (.3%). Extensive small bowel resection, resulting in less than 1.5 meters of remaining small bowel, was required in 7 patients (.01%). All patients with extensive small bowel resection presented with abdominal pain and had confirmed internal herniation as the cause of the small bowel resection, and 2 of 7 patients died. Closure of mesenteric defects was not associated with a reduction in overall small bowel resection rates (P = .89) CONCLUSION: Surgery for SBO after RYGB was common (6%). The risk of extensive small bowel resection leading to short bowel was low (.01%). Patients with abdominal pain after RYGB should be assessed for internal hernia, as it can be devastating.