Overview

This surgery is a simplified version of Roux-en-Y Gastric Bypass, developed to reduce operative time and complications. A long, narrow gastric pouch is created and connected to the small intestine with a single anastomosis (surgical connection) — hence “one anastomosis.”

Mechanism of Action

• Restrictive: Reduces stomach volume.

• Malabsorptive: Bypasses part of the small intestine, limiting nutrient absorption.

• Hormonal changes: Similar to RYGB.

Benefits

• Simpler procedure than Roux-en-Y — faster surgery time.

• Significant weight loss — similar or better than traditional bypass.

• Can be used as a revisional surgery after failed gastric sleeve or band.

Risks/Complications

• Bile reflux: A major concern; since the food and bile share the same pathway, bile can back up into the stomach or esophagus.

• Risk of nutrient malabsorption.

• May not be accepted or reimbursed in all countries (regulatory differences).

Ideal Candidates

• Patients wanting a bypass but with fewer surgical risks.

• Individuals who failed previous restrictive surgeries.

• Patients in need of significant metabolic improvement (e.g., uncontrolled diabetes).