One Anastomosis Gastric Bypass

The One anastomosis gastric bypass (i.e. OAGB) is also known as either the “mini” bypass or Single anastomosis bypass. It is similar to the Roux-en Y gastric bypass, but has a different benefit/ risk profile. Like the Roux-en Y gastric bypass, this procedure combined with diet and lifestyle changes, enables significant weight loss as well as improvement in obesity related metabolic diseases e.g. diabetes.

The gastric bypass procedure takes between 1-2 hours and is performed using key hole technique. This involves making several small incisions (between 5 and 12mm in length) into the abdomen where the surgical instruments, including a camera, are inserted. The top of the stomach is then stapled to form a small pouch (that is able to hold 30-50ml), which becomes the new, smaller, stomach and is completely separate to the rest of the stomach. A single join is then formed linking the new stomach pouch to the small intestine (the jejunum) so that the first part of the small intestine (the duodenum) is bypassed.

The procedure helps patients through several means:

• Reducing the size of the stomach. This limits the amount of food that can be eaten at any one time to less than a 1/4 of what you can eat now.
• Decreasing the amount of calories you absorb from your food as a result of bypassing the duodenum (the first part of the small intestine)
• Metabolic changes in the bypassed gut that aid in reversing the progression of metabolic diseases like diabetes.

Coupled with healthy lifestyle changes, the one anastomosis gastric bypass can provide powerful results. More detailed information about healthy eating behaviours will be provided during your visit with the dietitian.

Weight loss benefits and metabolic advantages:

• Proven method of long-term weight loss – averaging 70% of excess body weight loss (25-35% of their total body weight) in the first 12-24 months.
• Significantly reduces the burden of obesity related metabolic and physical disease like diabetes, hypertension, obstructive sleep apnoea, musculoskeletal disease etc. (there is growing evidence that its metabolic benefits exceed the Roux-en Y gastric bypass and sleeve gastrectomy)
• Effective for people who tend to prefer high sugar or high fat foods although this can precipitate a condition called dumping syndrome.

Who is suitable for the one anastomosis gastric bypass?

• Patients with BMI >30 with obesity related conditions
• Patients with BMI >35 with or without any obesity related conditions

How is the recovery and diet post procedure?

Patients routinely stay in hospital for 2-3 days after the surgery before discharge. The main aim in the immediate post operative period is to get used to having a smaller stomach size, while working towards a daily fluid volume of 700-1000mls. You will also be prescribed anti-nausea and pain medications to keep you comfortable.

On discharge, most patients will remain on a high-energy protein liquid diet (pre-determined by the dieticians) for a duration of 2-3 weeks before progressing to a solid diet compressing of soft foods. You will also be on an anti-reflux medication along with commencement of a multi-vitamin tablet. It is important to maintain an adequate level of hydration throughout this period.

Typically, patients will feel that they can tolerate one quarter to one third of their previous meal quantity in the first 1-2 months post-surgery. Progressively over the first 12 months, the quantity of oral intake that patients can tolerate will increase, although there will always be a level of food restriction following the Roux operation.

Is the operation safe and what are some of the side effects?

The one anastomosis bypass is a safe operation especially in expert hands. This procedure has a different complications profile to the sleeve gastrectomy and Roux en Y gastric bypass. Even though complications from the operation is considerably rare, they can still occur. It is important to understand these risks before proceeding with the operation. Some of the post operative risks include blood loss, infections, problems associated with anaesthesia, deep vein thrombosis (blood clot in the leg), staple line leaks and ulcers around the surgically created bowel joins.

In the medium to long term, 10-15% of patients may develop bile reflux symptoms. Weight re-gain can be an issue for a small proportion of one anastomosis bypass patients, highlighting the importance of regular specialist follow up and optimum dietary/ lifestyle modifications. Dumping syndrome can occur more commonly with this procedure when compared to sleeve gastrectomy. Patients can also experience cramping, diarrhoea, nausea, fatigue, light-headiness and sweating following large carbohydrate meals. Similar to the Roux bypass, patients undergoing this procedure are at risk of nutritional deficiencies. Regular follow-up is as such, very important with our practice regularly monitoring you for this

The listed complications are not intended to worry you, but simply inform you about the range of possible complications, regardless of how rare some of them may be. Our team takes measures directly aimed at reducing these risks, but if complications occur, additional treatment may be necessary.