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.