The digestive process begins in the mouth, where chewing and saliva breakdown food. Digestion continues in the stomach, where food is turned into a liquid called chyme.
Chyme next passes into the small intestine. Here, enzymes from the pancreas and liver further digest food. It is also in the small intestine where all nutrients and vitamins are absorbed. Small fingerlike projections lining the small intestine, called villi, enable digested food to enter the bloodstream.
Biliopancreatic diversion (BPD) with switch is a combination restrictive and malabsorptive procedure. The goal of this surgery is to induce weight loss by altering the digestive tract so that nutrients and fats are not absorbed by the body.
During the first part of the procedure, the size of the stomach is surgically reduced in a procedure called a gastrectomy. The pyloric valve, which regulates the release of stomach contents into the small intestine, and a short segment of the duodenum, the first section of the small intestine, are left in place. By preserving this part of the digestive tract, the frequent complication of gastric "dumping" is reduced.
The next component of BPD with switch procedure is the division of the small intestine. This step separates the flow of food through the digestive tract from the flow of bile and pancreatic juices. While this reduces absorption of nutrients and fats from the small intestine into the bloodstream, it still allows the body to utilize the digestive enzymes. The two sections of small intestine are rejoined further along the intestinal tract, near the large intestine. This allows food and digestive enzymes to mix and digest normally.
The BPD with duodenal switch is a complicated weight-loss procedure that has demonstrated successful long term weight loss.