When the “Y” Becomes an “O”: A Narrative Review of Roux-en-O Complication After Roux-en-Y Gastric Bypass—Incidence, Diagnosis, Management, and Prevention

Roux-en-O misconfiguration is a rare but serious technical error in Roux-en-Y gastric bypass (RYGB), resulting from the misidentification of small bowel limbs in which the biliopancreatic limb (BPL) is incorrectly anastomosed to the gastric pouch and the jejunojejunostomy (JJ) is misconfigured, leading to functional obstruction, bile reflux, and substantial morbidity. This narrative review synthesizes the available literature on its incidence, risk factors, clinical presentation, diagnostic challenges, differential diagnosis, treatment strategies, associated morbidity, and prevention methods. Drawing from case reports and small series, we highlight the diagnostic pitfalls and surgical corrections, including innovative approaches like jejunal interposition for complicated revisions. An illustrative case of a young woman with Roux-en-O following multiple bariatric conversions, complicated by a perigastric abscess, is integrated to demonstrate real-world application. Early recognition and meticulous intraoperative verification are essential to mitigate this preventable complication, preserving the efficacy of RYGB as a benchmark bariatric procedure.