**4.2 One anastomosis gastric bypass (OAGB)**

The OAGB was created to compensate for the technical complexity of the RYGB. The procedure has two main components: a long and narrow gastric pouch and a 150–200 cm jejunal bypass (biliopancreatic limb) with a single anastomosis, the gastrojejunostomy. The stomach is divided parallel to the lesser curvature creating a narrow and longitudinal gastric pouch after passing a bougie for sizing, preserving the pylorus. The anastomosis between the jejunum and the gastric pouch is done 150–200 cm distal to Treitz's ligament.

The percentage of weight loss and the improvement and resolution of associated comorbidities especially diabetes is similar in both, RYGB and OAGB. As with all the procedures involving duodenal exclusion, nutritional supplementation is needed although a higher risk for iron and fat-soluble vitamins deficiency has been observed with OAGB due to the length of the biliopancreatic limb which is believed to aggravate malabsorption. This has led to some surgeons reducing the length of the limb from the 200 cm size to 150 cm in patients, especially with a body mass index (BMI) < 50 kg/m2.

Despite sharing some complications with RYGB such as the risk of hemorrhage, anastomotic ulcer, anastomotic leak, dumping syndrome, and hypoglycemia, fewer side effects can be expected [21]. The fact that there is only one anastomosis, and the

**Figure 2.** *One anastomosis gastric bypass.*
