The Basics of Bariatric Surgery (Continued)
Combined Restrictive/Malabsorptive Operations
Combined operations are the most common bariatric procedures. They restrict both food intake and the amount of calories and nutrients the body absorbs.
1. Roux-en-Y gastric bypass (RGB). This operation, illustrated in color figure 4 at top, is the most common and successful combined procedure in the United States. First, the surgeon creates a small stomach pouch to restrict food intake. Next, a Y-shaped section of the small intestine is attached to the pouch to allow food to bypass the lower stomach, the duodenum (the first segment of the small intestine), and the first portion of the jejunum (the second segment of the small intestine). This reduces the amount of calories and nutrients the body absorbs. Rarely, a cholecystectomy (gall bladder removal) is performed to avoid the gallstones that may result from rapid weight loss. More commonly, patients take medication after the operation to dissolve gallstones.
2. Biliopancreatic diversion (BPD). In this more complicated combined operation, the lower portion of the stomach is removed (see color figure 5 at bottom). The small pouch that remains is connected directly to the final segment of the small intestine, completely bypassing the duodenum and the jejunum. Although this procedure leads to weight loss, it is used less often than other types of operations because of the high risk for nutritional deficiencies. A variation of BPD includes a duodenal switch (see figure 6), which leaves a larger portion of the stomach intact, including the pyloric valve that regulates the release of stomach contents into the small intestine. It also keeps a small part of the duodenum in the digestive pathway. The larger stomach allows patients to eat more after the weight loss surgery than patients who have other types of procedures.
Advantages: Most patients lose weight quickly and continue to lose for 18 to 24 months after the procedure. With the Roux-en-Y gastric bypass, many patients maintain a weight loss of 60 to 70 percent of their excess weight for 10 years or more. With BPD, most studies report an average weight loss of 75 to 80 percent of excess weight. Because combined operations result in greater weight loss than restrictive operations, they may also be more effective in improving the health problems associated with severe obesity, such as hypertension (high blood pressure), sleep apnea, type 2 diabetes, and osteoarthritis.
Disadvantages: Combined procedures are more difficult to perform than the restrictive procedures. They are also more likely to result in long-term nutritional deficiencies. This is because the operation causes food to bypass the duodenum and jejunum, where most iron and calcium are absorbed. Menstruating women may develop anemia because not enough vitamin B12 and iron are absorbed. Decreased absorption of calcium may also bring on osteoporosis and related bone diseases. Patients must take nutritional supplements that usually prevent these deficiencies. Patients who have the biliopancreatic diversion procedure must also take fat-soluble (dissolved by fat) vitamins A, D, E, and K supplements, and require life-long use of special foods and medications.
RGB and BPD operations may also cause dumping syndrome, an unpleasant reaction that can occur after a meal high in simple carbohydrates, which contain sugars that are rapidly absorbed by the body. Stomach contents move too quickly through the small intestine, causing symptoms such as nausea, bloating, abdominal pain, weakness, sweating, faintness, and sometimes diarrhea after eating. Because the duodenal switch operation keeps the pyloric valve intact, it may reduce the likelihood of dumping syndrome.
Risks: In addition to risks associated with restrictive procedures such as infection, combined operations are more likely to lead to complications. The risk of death associated with these types of procedures is lower for the gastric bypass (less than 1 percent of patients) than for the biliopancreatic diversion with duodenal switch (2.5 to 5 percent). Combined operations carry a greater risk than restrictive operations for abdominal hernias (up to 28 percent), which require a follow-up operation to correct. The risk of hernia, however, is lower (about 3 percent) when laparoscopic techniques are used.
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