Title: One Anastomosis Gastric Bypass-Key Technical Features, and Prevention and Management of Procedure-Specific Complications Short Title: One Anastomosis Gastric Bypass Authors:

Introduction: One Anastomosis Gastric Bypass (OAGB) is now a recognised mainstream bariatric procedure being adopted by an increasing number of surgeons. The purpose of this review was to present an evidence-based summary of its key technical aspects and prevention and management of its specific complications. Evidence Acquisition: We examined PubMed for all published articles on OAGB, including the ones published under one of its various other names. Evidence Synthesis: An ideal OAGB procedure has a long, narrow pouch constructed carefully to avoid going too close to the greater curvature of the stomach especially at the bottom of the pouch, and maintains a safe distance from the angle of His. A Bilio-Pancreatic limb length of 150 cm appears to be safest and a limb length of > 200 cm is associated with a significantly increased incidence of protein-calorie malnutrition. We recommend routine closure of Petersen's space to prevent Petersen's hernia and suggest a protocol for micronutrient supplementation. This review also presents evidence-based algorithms for prevention and management of marginal ulcers, protein-calorie malnutrition, and Gastro-Oesophageal Reflux Disease after OAGB. We suggest lifelong supplementation with two multivitamin/mineral supplements (each containing at least 1.0 mg Copper and 15 mg Zinc) daily, 1.5 mg vitamin B12 orally daily or 3-monthly injection with 1 mg vitamin B12, 120 mg elemental iron daily, 1500 mg elemental Calcium daily, and 3000 international units of vitamin D daily. Conclusion: This review examines key technical steps of OAGB. We also discuss how to prevent and manage its specific complications.