Gastric Bypass Surgery

There are two common types of ‘Bypass’ procedures

THE CLASSIC

Roux-en-Y gastric bypass (RYGB)

The Roux-en-Y Gastric Bypass (RYGB) is the original and as such is commonly referred to as simply a “Gastric Bypass.” Since its inception in 1967, it has become one of the most popularly performed bariatric procedures worldwide and has long been considered the “gold standard” of bariatric surgery. 

Bypass surgery was performed as open surgery for several decades, but today it is almost entirely performed by the laparoscopic (keyhole) approach.

The operative procedure involves staple dividing the stomach into two chambers.

The upper chamber (pouch) receives food and has Avery small volume capacity. The lower chamber (remaining stomach) is “bypassed” and does not receive food. 

The small intestine is divided and one end is connected (“anastomosed”) to the pouch. A second connection (“anastomosis”) is made to connect the disconnected stomach and duodenum to the small bowel. This connection enables the digestive fluids to meet the ingested food to enable nutrient breakdown and absorption. 

After the procedure is completed, food advances directly from the small gastric pouch to the small intestine without passing through the lower portion of the stomach, duodenum and upper small bowel (jejunum) 

This gastric bypass can help facilitate weight loss in several different ways. Firstly, the small pouch restricts the amount of food that can be eaten. The connection between the small bowel and the gastric pouch re-routes the transit of food directly in to the small bowel. Since the food does not go through the bypassed portion of the stomach and duodenum there are metabolic and hormonal changes that lead to reduced appetite and an increased feeling of fullness.

RYGB typically results in 65 to 75% excess body weight loss.

The maximum effect on weight loss is normally observed during the first 18 months. There is typically some weight regain but most studies suggest that most patients will maintain satisfactory weight loss even after 10 years.

In addition to weight loss, several obesity related diseases will typically improve after surgery. These include type 2 diabetes, hypertension, dyslipidemia, metabolic syndrome, fatty liver disease, and obstructed sleep apnea. In fact, more than 50% of patients with type 2 diabetes will experience normalisation of their blood sugar levels and will either be off all of their anti-diabetic medications or require markedly less medications.

At centres that do a large number of bariatric procedures each year, the risk of postoperative complications is low. The risk of dying from the surgery is less than 0.2% and the risk of severe complications such as bleeding, infections and thromboembolism is less than 5%. Gastric bypass surgery is currently as safe as gallbladder surgery.

However, the gastric bypass procedure can result in significant vitamin and mineral deficiencies including Iron, vitamin B12, vitamin B1, calcium, zinc, vitamin D and folate. Therefore, as with all bariatric procedures, the patients who undergo gastric bypass require life-long surveillance and vitamin and mineral supplementation.

Common risks:

• ‘Dumping syndrome’ with certain foods 

• Internal hernia (approx. 3% life time risk)

• Narrowing of the joins (anastomosis)

• Ulcer at the join (low risk in non smokers)

ONE ANASTOMOSIS GASTRIC BYPASS (OAGB)

‘Mini’ Gastric Bypass

The One Anastomosis Gastric Bypass (OAGB), also known as the “mini” was first reported in 2001. 

The OAGB is a minimally invasive procedure performed with laparoscopic technique. During a OAGB procedure, the surgeon first reduces the size of the “working” stomach by separating a tube-like pouch of stomach from the rest of the stomach. This tubular gastric pouch is then connected (anastomosed) to the intestine, bypassing 150–200cm of the upper part of the intestine. This technique differs from the traditional Roux-en-Y Bypass (RYGB) which requires two connections (anastomoses).

OAGB advantages:

• One connection

• Longer pouch

A OAGB typically results in 60-80% excess weight loss. The most rapid weight loss occurs in the first 6 months after surgery and then continues at a slower pace for up to another 18 months.

This weight loss is achieved through both restriction (the new gastric pouch can hold only a small quantity of food) and malabsorption. Bypassing a sizable segment of the intestine, the remaining intestine is not long enough for normal nutrient absorption leading to malabsorption. The substantial weight loss may lead dramatic improvement, and even complete remission of many of the obesity-related co-morbidities. 

Long-term data shows that the OAGB may result in a slightly higher weight loss and better resolution of diabetes than the RYGB. The superior diabetes remission rate in OAGB might be attributed to both the greater weight loss and the longer by-passed limb.

The advantage of the OAGB is it’s a safe procedure with low rate of complications such as leaks and bleeding.

Long term, the OAGB, results in fewer intestinal obstruction problems and less risk for internal herniation.

As stated above, over the long-term, a OAGB usually brings about better weight loss and a higher diabetes resolution rate than a RYGB. 

The OAGB has few long term complications. Less than 5% of the patients may require revision surgery, with half of the revisional surgeries due to severe malnutrition and the other half due to bile reflux, ulcer and/or weight regain.

Disadvantages of the OAGB include a greater likelihood that patients with OAGB will experience greater bile reflux than after a RY gastric bypass, which can adversely affect their quality of life. Another disadvantage of OAGB a greater likelihood to develop significant vitamin and micronutrient deficiencies over time. Patients receiving OAGB must take regular vitamin and mineral supplements as instructed, and undergo lifelong, yearly monitoring. Finally, with the OAGB procedure, similar to RYGB it is difficult if not impossible access the excluded gastric remnant for endoscopy.