Gastric bypass surgery combines the creation of a small stomach pouch to restrict food intake and construction of bypasses of the duodenum and other segments of the small intestine to cause malabsorption (decreased ability to absorb calories and nutrients from food).
Types of Gastric Bypass Surgery
- Roux-en-Y gastric bypass (RGB): This operation is the most common gastric bypass surgery performed in the U.S. First, a small stomach pouch is created by stapling part of the stomach together or by vertical banding. This limits how much food you can eat. Next, a Y-shaped section of the small intestine is attached to the pouch to allow food to bypass the duodenum as well as the first portion of the jejunum. This causes reduced calorie and nutrient absorption. This procedure can now be done with a laparoscope (a thin telescope-like instrument for viewing inside the abdomen) in some people. This involves using small incisions and generally has a more rapid recovery time.
- Extensive gastric bypass (biliopancreatic diversion): In this more complicated gastric bypass operation, the lower portion of the stomach is removed. The small pouch that remains is connected directly to the final segment of the small intestine, thus completely bypassing both the duodenum and jejunum. Although this procedure successfully promotes weight loss, it is not as widely used because of the high risk for nutritional deficiencies.
Gastric bypass surgery that causes malabsorption and restricts food intake produces more weight loss than restriction operations like gastric banding, which only decrease food intake. People who have bypass surgery generally lose two-thirds of their excess weight within two years.
Risks of Gastric Bypass Surgery
People who undergo gastric bypass surgery are at risk for:
- Pouch stretching (stomach gets bigger overtime, stretching back to its original size).
- Band erosion (the band closing off part of the stomach disintegrates).
- Breakdown of staple lines (band and staples fall apart, reversing the procedure).
- Leakage of stomach contents into the abdomen (this is dangerous because the acid can eat away other organs).
- Nutritional deficiencies causing health problems.
Gastric bypass surgery also may cause "dumping syndrome," whereby stomach contents move too rapidly through the small intestine. Symptoms include nausea, weakness, sweating, faintness, and, occasionally, diarrhea after eating, as well as the inability to eat sweets without becoming extremely weak. Gallstones can occur in response to rapid weight loss. They can be dissolved with medication taken after the surgery.
Complications From Nutritional Deficiencies
The limited absorption of vitamin B-12 and iron can cause anemia. The lack of calcium absorption can cause osteoporosis and metabolic bone disease. People who undergo this procedure are required to take nutritional supplements that usually prevent these deficiencies.
The more extensive the gastric bypass surgery, the greater the risk for complications and nutritional deficiencies. People who undergo extensive bypasses of the normal digestive process require not only close monitoring, but also lifelong use of special foods and medications.
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National Institute of Diabetes and Digestive and Kidney Diseases.
Reviewed by Kimball Johnson, MD on May 26, 2012
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