Malabsorptive gastric bypass - Roux-en-Y and Biliopancreatic diversion

Shrinking the Bowel to Cut Back Caloric Absorption

Malabsorptive procedures promote weight loss by bypassing a large portion of the small intestine to decrease absorption of nutrients and calories. With the intestinal bypass, these surgeries also create a small pouch to restrict the food intake. These surgeries, therefore, are more compelling and confer a greater weight loss than the restrictive surgeries. Patients may lose up to 66% of their surplus weight within two years of surgery. 

There are two primary types of malabsorptive surgeries

Roux-en-Y gastric bypass (RGB)

This procedure creates an upper stomach pouch of a capacity of 1-2 ounces, by stapling or by vertical banding method to restrict the intake of food. A roux limb connects this pouch midway along the intestine (bypassing the duodenum and some part of jejunum) for the flow of food into the intestine. The remaining, bigger portion of the stomach is connected to the small intestine beyond the point of connection of small pouch to bring the gastric juices. Thus, with the connection of small pouch and the other part of stomach to the small intestine, a Y-shaped structure forms and so the surgery derived its name. The purpose of RGB is two-fold:

• To limit the intake of food (by creating stomach pouch)

• To cut off the absorption of nutrients and calories (by bypassing the duodenum and a fraction of jejunum)

RGB is the most effective bariatric surgeries to promote weight loss and referred as the gold standard. All other bariatric surgeries must match it.

Biliopancreatic diversion (BPD)

This is a more complicated malabsorptive surgery and removes the distal part of the stomach. This procedure involves creation of a small pouch in the upper part of stomach. A roux limb connects the pouch to the small intestine, bypassing the duodenum and the jejunum. A bioliopancreatic limb gets digestive juices from the gall and pancreas into the intestine, where the food brought by roux limb is digested. BPD is an effective weight loss surgery but has a high risk for nutritional deficiencies because of which it is done less often.

The duodenal switch, a BPD, does not remove parts of stomach. It also leaves the first portion of duodenum intact so the incidence of stomal ulcers reduces with this surgery.

Malabsorptive procedures carry a higher risk

Although malabsorptive surgeries confer more weight loss than the restrictive surgeries, they carry a greater risk of nutritional deficiency. Since duodenum is a major site for the absorption of iron and calcium, its bypass poses a threat of problems like anemia and osteoporosis. A patient needs supplementation of minerals and vitamins throughout his life following these surgeries. ‘Dumping syndrome’ is also more frequent after malaborptive procedures since the food passes more quickly. It may lead to nausea, weakness, fainting, and diarrhea.