One Anastomosis Gastric Bypass

Kamal Mahawar

Consultant General Surgeon, Sunderland Royal Hospital, Sunderland, UK Visiting Professor, University of Hospital, Sunderland, UK

The One Anastomosis Gastric Bypass(OAGB) was first reported in 2001 and is now the third commonest primary, bariatric procedure worldwide. An OAGB involves the creation of a long, narrow gastric pouch which is then connected to the small intestine bypassing approximately 150 cm of the upper part of the small intestine (Figure 1). It takes approximately 90-100 minutes to perform and is usually performed laparoscopically (through keyhole surgery). Most patients are admitted on the day of surgery and can expect to go home in a day or two after surgery.

It is a remarkably effective bariatric procedure with weight loss and co-morbidity (such as type 2 diabetes and high blood pressure) improvement outcomes that are similar, if not better, to the Roux-en-Y Gastric Bypass (RYGB) and slightly better than Sleeve Gastrectomy (SG). Most patients can expect a weight loss of 30-40% from baseline. Usually, patients reach their nadir weight at around 6-12 months after bariatric surgery. The weight-regain that some patients experience after the first year is lower with an OAGB than with SG or RYGB.

We do not clearly understand the mechanism of action of most bariatric procedures including OAGB. However, it is increasingly being recognised that the effects are probably mediated through yet incompletely understood neuro-hormonal signals.

The procedure can be performed with remarkable safety. The risk of death from early complications of surgery (such as bleeding, leak, pulmonary embolism, etc.) is approximately 0.1 -0.2%. Risk of major complications that may require further intervention is approximately 2.0-3.0% in the early period after surgery. In the long-term, the three commonest complications associated with this procedure are ulcer at the joint between the stomach, malnutrition, and acid/bile reflux.

The risk of ulcers can be reduced by prophylaxis with acid-reducing medications and patients need to adopt a healthy diet and take life-long iron, vitamin D, Calcium, Vitamin B12, Folate, and multivitamin-mineral supplements. There is a risk of severe malnutrition and acid/bile reflux that can require further surgery. Overall approximately 5.0% of patients need further surgery in the long-term for malnutrition or severe symptoms of acid/bile reflux. Like any other bariatric procedure, patients should undergo lifelong, annual follow-up and monitoring for early diagnosis and treatment of any vitamin/mineral deficiency.

Abbreviations:

OAGB: One Anastomosis Gastric Bypass

RYGB: Roux-en-Y Gastric Bypass