ABOUT THE PROCEDURE

One anastomosis gastric bypass (OAGB), previously known as mini gastric bypass (MGB), or omega loop gastric bypass, or single anastomosis gastric bypass (SAGB), is increasing in popularity as an option for bariatric (weight loss) surgery in Australia. It has been available in Australia since the mid-2000s.

In this procedure, a small section of the blood vessels attached to the right side of the stomach (lesser curvature) is divided and then a calibrated sizing tube is passed through the mouth to the stomach by the anaesthetist.

A surgical stapler is positioned externally on the stomach against the internal tube. The stapler is fired in such a way that a small gastric pouch, with a volume of approximately 60mL is formed using the upper right corner of the stomach (see diagram).

The gastric staples are permanent and do not need to be removed. They are safe with MRI scanners and are too small to be detected by airport security systems.

The remaining stomach is not removed, but now is unable to receive food. This unused portion of stomach, called the bypassed stomach or remnant stomach, still makes gastric acid and this acid passes to the first part of the intestine in the normal fashion.

To finish, surgery is performed with a combination of staples and sutures to connect a continuous (undivided) loop of small bowel to the upper gastric pouch. This connection point is called an anastomosis. The length of small intestine that is bypassed is usually between 150 and 200cm (shown in white on the diagram). In this operation, there is only 1 anastomosis.

RECOVERY

The surgery is performed laparoscopically (keyhole) in almost all cases with 5 small incisions in the upper abdomen. The average time in hospital after surgery is 2 nights. Office work can usually recommence after 2 weeks. Heavy work can recommence after 4 weeks.

RESULTS

This surgery results in a sensation of feeling full with much smaller quantities of food. Typically, an entree-size plate will provide the same feeling that a full dinner plate did before surgery. The surgery also leads to a reduction in certain hunger-promoting hormones, meaning that patients notice either the absence of or a decrease in the intensity of hunger between meals.

On average, patients who have a one-anastomosis gastric bypass will lose around 35% of their total body weight, or between 70-80% of their excess body weight. Maximum weight loss is usually achieved between 12-18 months.

ADVANTAGES

Much lower risk of developing gastro-oesophageal reflux than a sleeve gastrectomy
More weight loss than a sleeve gastrectomy (average 35% v 30% of total body weight)
No organ tissue removed so potentially reversible
More sustained weight loss compared to a sleeve gastrectomy (30% v 25% total body weight loss at 7 years)
Identical weight loss to a Roux-en-Y gastric bypass
Higher diabetes remission rate than a sleeve gastrectomy
Lower risk of internal hernia than a Roux-en-Y gastric bypass
Less operative time than a Roux-en-Y gastric bypass, and therefore lower cost
Less surgical risk than Roux-en-Y gastric bypass due to having one anastomosis

DISADVANTAGES

Bile reflux into the oesophagus requiring future conversion to Roux-en-Y gastric bypass occurs in 5%
Operation is not suitable for certain patient groups such as smokers, Crohn’s disease, those on certain long-term medications, future organ transplant recipients, those with very significant bowel adhesions, or any condition requiring surveillance of the stomach or duodenum for cancer
Internal hernia possible but uncommon
Anastomotic ulcer formation - highest risk in smokers
Anastomotic stricture (excessive narrowing)
Dumping syndrome more likely than sleeve gastrectomy
Nutrient deficiencies, especially if non-compliant with supplements
Remnant stomach and duodenum extremely difficult to access by endoscopy
If gallstones were to be present in the bile duct, management will be more complex