Gastric Bypass

Gastric Bypass has been with us for a long time and therefore we know a lot about its strengths and weaknesses. It was first described about 50 years ago and we have been doing the procedure for at least 35 years. It has been a very good procedure which has stood the test of time. It leads to good weight loss, many health benefits and better quality of life. But it is a complex procedure which carries significant short term risks and long-term side-effects. It is irreversible and not adjustable. As a result, it has never been enthusiastically embraced by more than a tiny fraction of the millions of people with obesity.

There are two versions of the Gastric Bypass that are used in Australia, the Roux en Y Gastric Bypass (RYGB) which is the original procedure from the 1970s and the Single Anastomosis Gastric Bypass (SAGB) which has been used for about 25 years. This is sometimes also called the Omega Loop Gastric Bypass and the Mini Gastric Bypass. They are all the same procedure.

The RYGB and the SAGB are shown in the two figures below. Both achieve almost identical results across many measures of effects but, because the SAGB is a simpler and therefore safer procedure and has slightly better weight loss and better effect with diabetes, it tends to be preferred.

Roux-en-Y Gastric Bypass (RYGB)
For the RYGB we totally separate a very small pouch of stomach from the rest of the stomach using a stapling device. The pouch has a volume of about 30-50 ml, equal to two to three tablespoons. The rest of the stomach (typically one to two litre volume) is sealed off and no longer accessible or used. The upper small intestine, the jejunum, is divided and the distal end of this division is brought up to the small pouch and joined to it. All food and fluids from then on pass down the oesophagus, into the small pouch of stomach and then straight into the jejunum. The proximal end of the divided jejunum is re-joined to jejunum much further down so that the secretions from the excluded stomach, the liver, pancreas, duodenum and upper jejunum can then join in helping with digestion.

Single Anastomosis Gastric Bypass (SAGB)
For the SAGB we still separate a small stomach from the remainder, using a stapling device but the pouch is structured to be more like a tube. The jejunum is not divided but is simply brought up and joined to the tube of stomach. All the digestive fluids from the excluded stomach plus the liver, pancreas, duodenum and upper jejunum meet the food at this join and pass down the remainder of the gut.


The first strength of the gastric bypass is its longevity. We have been using it for a long time and understand its strengths and weaknesses.

Effective in achieving substantial weight loss
It is effective in achieving substantial weight loss although there is some weight regain over the years as it is a non-adjustable procedure. The weight regain will probably prove to be less than we expect to find with sleeve gastrectomy when we get some long-term follow-up data for the sleeve.

Better aftercare than Lap-Band procedure
At the Centre for Obesity Research and Education (CORE), our research centre at Monash University, we have compared the world published literature for weight loss for gastric bypass and Lap-Band at 10 or more years of aftercare and found they are equal. But the gastric bypass is better than the Lap-Band in the first 2 years. We show this comparison in Figure 1 above. 
Along with the strong effect on weight, the gastric bypass has been well shown to be effective in controlling many of the co-morbidities also,


Complex procedure
Gastric bypass is a complex procedure that involves considerable stapling. It therefore carries much more risk than the Lap-Band. The risks of complications or death around the time of operation for the gastric bypass and the sleeve are probably about equal.

Potential nutritional problems
The gastric bypass changes the pathways for food and digestive juices. These can lead to nutritional problems due to malabsorption of micro-nutrients including deficiencies of iron, vitamin B12 and folic acid.

Dumping syndrome
Dumping syndrome can be a significant problem for some patients after gastric bypass. Dumping occurs because of the rapid transfer of swallowed foods straight into the small intestine and leads to feelings of faintness, weakness, abdominal cramps and the need to lie down after eating.

The gastric bypass, in theory, can be reversed but it is quite complex and almost never done. Also, it is non-adjustable.

Revisional surgery may be required
Revisional surgery or other procedures can be required if the pouch becomes too big or the opening into the jejunum becomes too wide. Blockage of the bowel can occur due to internal hernias that result from the reorganization of the jejunum.

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