Gastric Bypass

Gastric bypass

Roux-en-Y Gastric Bypass.
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The Roux-en-Y gastric bypass is the most commonly performed operation worldwide to achieve weight loss. In a gastric bypass, the stomach is partitioned in to a small pouch where food goes, that is approximately two tablespoons in size. The small intestine is then divided and joined directly to the ‘stomach pouch’. Finally the small intestine is reconnected downstream in a Y shaped configuration to allow stomach acid and digestive enzymes to mix with the food.

How it Works

Roux-en-Y gastric bypass has been performed since 1967, so it has the most amount of information about the long term outcomes after this surgery. It was initially performed as an open operation, but currently is usually performed as a laparoscopic or ‘keyhole’ operation. It works by interfering with the normal signals between the stomach, intestine and the brain that tell people that they are hungry or satisfied. In this way, people usually no longer feel ‘ravenous’ hunger, and also feel satisfied after eating very small meals. Early after a gastric bypass there is also a physical restriction of how much food can be eaten, and some calories are not absorbed because of the bypass. The effect of this decreases with time. Gastric bypass also has the side effect of ‘dumping’. This is when refined carbohydrates (sugar) are absorbed rapidly from the small intestine, and may result in feeling lightheaded, nauseated and dizzy. People who experience dumping tend to avoid food containing sugar, which also helps with weight loss.

Weight Loss

The average amount of weight people lose after a gastric bypass is determined in part by their starting body weight. In general, people who start off heavier, will lose more weight, although the proportion of body weight lost is more consistent. Average weight loss after a gastric bypass is 30 to 40% of starting body weight. For example, someone weighing 150kg, would lose an average of 45-60kg after surgery. This is an average figure, and it is impossible to predict the exact amount of weight any individual person will lose. Weight loss tends to occur over 12 to 18 months, and then people commonly regain a small amount of weight and reach a new plateau, or steady weight. A small number of people will lose a lot of weight, and a small number will regain a significant amount of weight, again this is difficult to predict.

Details and Risks

Laparoscopic Roux-en-Y gastric bypass is performed under a general anaesthetic (you are completely asleep). Usually people are in hospital for two nights after surgery, and go home tolerating a liquid diet and able to move about and care for themselves. After gastric bypass, certain vitamins and minerals are not absorbed as well because of the bypassed intestine. It is necessary therefore to take vitamin supplementation for life (multivitamin, calcium, iron). Gastric bypass is a major operation, and as with any operation, carries risks of potentially serious complications. However, in experienced hands, the modern laparoscopic Roux-en-Y gastric bypass is very safe, and the risks are comparable with having a major joint replacement operation. The risks of serious complications, requiring return to the operating room or intensive care admission are approximately 2 or 3 in 100. The risks of dying as a result of complications are 1 to 3 in 1000.

Gastric bypass is a permanent change to the digestive tract, and as such there are risks of late complications that may occur months or years after surgery. The most common is a stricture or narrowing at the join between the stomach pouch and small intestine. This usually occurs in the first six months after surgery, and can usually be treated with a single endoscopy (telescopic examination of the stomach). In people who smoke cigarettes, or take aspirin or anti-inflammatory drugs, this complication can be more severe, and very difficult to treat. Therefore, gastric bypass is not recommended in these circumstances. Blockages to the intestine may also occur because of the way the intestines have been rearranged. This may occur in approximately one in twenty people who have a gastric bypass. Surgery is usually required to treat this, however this surgery is usually relatively straightforward, and is not usually an emergency.

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