DISCLOSURE DOCUMENTS: SECTION 3

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Normally, as food moves along the digestive tract (see figure 1), appropriate digestive juices and enzymes arrive at the right place at the right time to digest and absorb calories and nutrients. After we chew and swallow our food, it moves down the esophagus to the stomach, where a strong acid continues the digestive process. The stomach can hold about 3 pints of food at one time. When the stomach contents move to the duodenum, the first segment of the small intestine, bile and pancreatic juice speed up digestion. Most of the iron and calcium in the foods we eat is absorbed in the duodenum. The jejunum and ileum, the remaining two segments of the nearly 20 feet of small intestine, complete the absorption of almost all calories and nutrients. The food particles that cannot be digested in the small intestine are stored in the large intestine until eliminated.

The concept of gastric surgery to control obesity grew out of results of operations for cancer or severe ulcers that removed large portions of the stomach or small intestine.

Because patients undergoing these procedures tended to lose weight after surgery, some physicians began to use such operations to treat severe obesity. The first operation that was widely used for severe obesity was the intestinal bypass. This operation, first used 40 years ago, produces weight loss by causing malabsorption. The idea was that patients could eat large amounts of food, which would be poorly digested or passed along too fast for the body to absorb many calories.

The problem with this surgery was that it caused a loss of essential nutrients and its side effects were unpredictable and sometimes fatal. The original form of the intestinal bypass operation is no longer used.

Surgeons now use techniques that produce weight loss primarily by limiting how much the stomach can hold. These restrictive procedures are often combined with modified gastric bypass procedures that somewhat limit calorie and nutrient absorption and may lead to altered food choices.

Two ways that surgical procedures promote weight loss are:

1. By decreasing food intake (restriction). Gastric banding, gastric bypass, and vertical-banded gastroplasty are surgeries that limit the amount of food the stomach can hold by closing off or removing parts of the stomach. These operations also delay emptying of the stomach (gastric pouch).
2. By causing food to be poorly digested and absorbed (malabsorption). In the gastric bypass procedures, a surgeon makes a direct connection from the stomach to a lower segment of the small intestine, bypassing the duodenum, and some of the jejunum.

Although results of operations using these procedures are more predictable and manageable, side effects persist for some patients.

Restriction operations are the surgeries most often used for producing weight loss. Food intake is restricted by creating a small pouch at the top of the stomach where the food enters from the esophagus. The pouch initially holds about 1 ounce of food and expands to 2-3 ounces with time. The pouch's lower outlet usually has a diameter of about 1/4 inch. The small outlet delays the emptying of food from the pouch and causes a feeling of fullness.

After an operation, the person usually can eat only a half to a whole cup of food without discomfort or nausea. Also, food has to be well chewed. For most people, the ability to eat a large amount of food at one time is lost, but some patients do return to eating modest amounts of food without feeling hungry.

Restriction operations for obesity include gastric banding and vertical banded gastroplasty. Both operations serve only to restrict food intake. They do not interfere with the normal digestive process.

Restrictive operations lead to weight loss in almost all patients. However, weight regain does occur in some patients. About 30 percent of persons undergoing vertical banded gastroplasty achieve normal weight, and about 80 percent achieve some degree of weight loss. However, some patients are unable to adjust their eating habits and fail to lose the desired weight. In all weight-loss operations, successful results depend on your motivation and behaviors.

A common risk of restrictive operations is vomiting caused by the small stomach being overly stretched by food particles that have not been chewed well. Other risks of VBG include erosion of the band, breakdown of the staple line, and, in a small number of cases, leakage of stomach juices into the abdomen. The latter requires an emergency operation. In a very small number of cases (less than 1 percent) infection or death from complications can occur.

These operations combine creation of small stomach pouches to restrict food intake and construction of bypasses of the duodenum and other segments of the small intestine to cause malabsorption.

Gastric bypass operations (figures 4 and 5) that cause malabsorption and restrict food intake produce more weight loss than restriction operations (figures 2 and 3) that only decrease food intake. Patients who have bypass operations generally lose two-thirds of their excess weight within 2 years.

The risks for pouch stretching, band erosion, breakdown of staple lines, and leakage of stomach contents into the abdomen are about the same for gastric bypass as for vertical banded gastroplasty. However, because gastric bypass operations cause food to skip the duodenum, where most iron and calcium are absorbed, risks for nutritional deficiencies are higher in these procedures. Anemia may result from malabsorption of vitamin B12 and iron in menstruating women, and decreased absorption of calcium may bring on osteoporosis and metabolic bone disease. Patients are required to take nutritional supplements that usually prevent these deficiencies.

Gastric bypass operations 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 so weak and sweaty that the patient must lie down until the symptoms pass.

The more extensive the bypass operation, the greater is the risk for complications and nutritional deficiencies. Patients with extensive bypasses of the normal digestive process require not only close monitoring, but also life-long use of special foods and medications.