Duodenal switch, one of the most complicated weight loss surgeries, is also known as vertical gastrectomy with duodenal switch, biliopancreatic diversion with duodenal switch.

Duodenal switch packs a one-two punch against obesity. It does so by combining two surgical techniques: restrictive and malabsorptive..

The restrictive component involves reducing the size of the stomach. Your bariatric surgeon would divide the stomach vertically and remove more than 85 percent of it. The stomach that remains is shaped like a banana and is about 100 to 150 milliliters or 6 ounces.

Duodenal switch surgery is a variation of another procedure, called biliopancreatic diversion. But the duodenal switch leaves a larger portion of the stomach intact, including the pyloric valve, which regulates the release of stomach contents into the small intestine

As the name suggests, the duodenal switch also keeps a small part of the duodenum in the digestive system. The duodenum is the first part of the small intestine. It is located between the stomach and the jejunum, or the middle part of the small intestine. Foods mix with stomach acid, then move down into the duodenum, where they mix with bile from the gall bladder and digestive juices from the pancreas.

Malabsorptive surgeries restrict the amount of calories and nutrients the body absorbs. The malabsorptive component of duodenal switch surgery involves rearranging the small intestine to separate the flow of food from the flow of bile and pancreatic juices. The food and digestive juices interact only in the last 18 to 24 inches of the intestine, allowing for malabsorption. Unlike the restrictive part of the surgery, the intestinal bypass part of the duodenal switch is partially reversible if you are one of the people who experience malabsorptive complications.

With the duodenal switch, you consume less food than normally, but it is still more than with other weight loss surgeries. Even this amount of food cannot be digested as normal, so a large amount of food passes through the shortened intestines undigested.

The duodenal switch can also be performed laparoscopically, meaning that your surgeon makes small incisions as opposed to one large incision. He or she inserts a viewing tube with a small camera (laparoscope) and other tiny insert instruments into these small incisions to perform the duodenal switch procedure.