Gastric Bypass (Malabsorptive) Surgery Procedure

Gastric bypass surgery, a type of bariatric surgery (weight loss surgery), is a procedure that alters the process of digestion. Bariatric surgery is the only option today that effectively treats morbid obesity in people for whom more conservative measures such as diet, exercise, and medication have not been effective.

Bariatric surgery works in one of three ways:

  • Restriction, or limiting the amount of food intake by reducing the size of the stomach
  • Malabsorption, or limiting the absorption of foods in the intestinal tract by "bypassing" a portion of the small intestine to varying degrees
  • Combination of both restriction and malabsorption

Currently, in the U.S., five types of bariatric surgical procedures are generally used to obtain continued weight loss. The purely restrictive bariatric surgeries are called gastric banding or gastric stapling. The biliopancreatic diversion with or without duodenal switch (BPD-DS) is mainly a malabsorptive bariatric surgery. Gastric bypass surgery is a combination of both restriction and malabsorption.

Types of bariatric surgical procedures that involve gastric bypass to some degree include:

Roux-en-Y gastric bypass (RYGBP)

Roux-en-Y gastric bypass is the most commonly performed bariatric procedure. It works by combining both restrictive and malabsorptive elements. The restrictive element can be achieved by stapling the stomach into two sections. The top section becomes a small pouch that serves as the "new" stomach. The small size of this newly formed stomach is so reduced that it "restricts" or limits the amount of food intake. It also provides a feeling of fullness and satisfaction with smaller portions of food. The lower section of the stomach no longer receives, stores, and mixes food but remains functional by continuing to secrete digestive juices.

The malabsorptive element in gastric bypass is achieved by surgically dividing the small intestine in a certain area. Once divided, the lower part of the intestine (jejunum) is pulled up to directly connect to the small pouch or "new" stomach. The other end of this divided intestine is surgically sewn back at a specific point further down the small intestine. The shape of the intestine now somewhat resembles a "Y." As a result, when food is eaten, it enters the "new" stomach, then travels into the jejunum, first "bypassing" the upper part of the intestine. The effect of bypassing the upper portion of the intestine decreases the amount of calories and nutrients that are absorbed into the body. This surgery can result in two-thirds of excess weight loss within two years. Because of the malabsorption, this increases the risk of nutritional deficiencies. Therefore, after surgery, it will be important to follow the physician's guidelines for nutritional supplementation.

The Roux-en-Y gastric bypass may be performed with a laparoscope rather than through an open incision in some patients. This procedure uses several small incisions and three or more laparoscopes, small thin tubes with video cameras attached, to visualize the inside of the abdomen during the operation. The surgeon performs the surgery while looking at a TV monitor. People with a Body Mass Index (BMI) of 60 or more or those who have already had some type of abdominal surgery are usually not considered for this technique. A laparoscopic method allows the physician to make a series of much smaller incisions. Laparoscopic gastric bypass usually reduces the length of hospital stay, the amount of scarring, and results in quicker recovery than an open procedure.

Biliopancreatic diversion (BPD)

A biliopancreatic diversion is primarily malabsorptive, and is a more complicated procedure than the Roux-en-Y gastric bypass. In this procedure a part of the lower stomach is removed. The part of stomach that is left is connected directly to the last part of the small intestine (jejunum). As food is digested, it completely bypasses a larger section of the small intestine than in the Roux-en-Y gastric bypass. This surgery may result in a greater degree of malabsorption than the Roux-en-Y, resulting in greater nutritional deficiencies. It is not as commonly performed.

A variation of the biliopancreatic diversion is a procedure called the duodenal switch (BPD-DS). This adaptation retains the part of the stomach that includes the valve that controls the release of food into the small intestine. This helps to prevent the "dumping syndrome" which can result in vomiting or diarrhea. A small part of the upper intestine (duodenum) is also retained.

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