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Dr. Bruno Dillemans

General & obesity surgeon

Omega Loop Gastric Bypass

The Omega Loop Gastric Bypass, also known as a Mini-Gastric Bypass or Single Anastomose Gastric Bypass is a combination of restriction and malabsorption and therefore has a two-way weight reducing effect. This variation of a classic gastric bypass (Roux-en-y) has a different site of connection between the small bowel and the stomach with a single anastomosis, and features a longer gastric pouch.

The Omega Loop Gastric Bypass works by decreasing food intake, limiting the amount of food the stomach can hold by closing off a significant portion of the stomach and delaying the emptying of the stomach (gastric pouch). This results in a longer fullness feeling. Contrasting the classic gastric bypass there is also a more pronounced malabsorption, mainly from fats.

The procedure is fully reversible.

The Omega Loop Gastric Bypass achieves its effects by creating a small elongated stomach pouch from which the rest of the stomach is permanently divided and separated. Below the staple line the stomach keeps obtained but no food will enter here. The stomach will still produce gastric juices and enzymes essential for digestion and absorption of nutrients. The small intestine with these enzymes is connected with a single anastomosis after about 6,5 foot as an outlet to the stomach pouch.

Difference with the classic Gastric Bypass:

The main advantage of the Omega Loop or Mini Gastric Bypass is that there is only one anastomosis (stomach>bowel) instead of two with the classic gastric bypass (stomach>bowel and bowel>bowel). The weight loss in very obese patients seems better due to the more pronounced malabsorption.

The main disadvantage is that bile can directly enter the stomach, possibly even into the esophagus. This chronic bile reflux could be associated with an elevated risk of malignancy in periods longer than 30 years and is the reason Mini Gastric Bypass is not officially approved in the United States of America. The malabsorption can also give iron deficiency, anemia and diarrhea.

The procedure

The Omega Loop or Mini Gastric Bypass is always performed under general anesthesia and laparoscopically. Postoperatively you stay for 2 to 3 nights in the hospital. As noted before: this procedure is reversible!


Currently we only propose the Omega Loop or Mini Gastric Bypass to patients older than 50 years with a BMI higher than 45.

Possible complications

Cfr. the classic Gastric Bypass and the disadvantages discussed earlier

The effect on nutrition is the same as the classic Gastric Bypass.