The top of the stomach is stapled to form a thin tube (30ml to 50ml in size). The thin tube becomes the new, smaller stomach and is completely separate to the rest of the stomach. This stomach is then anastomosed to a loop of the small intestine, bypassing the first part of the intestine called the duodenum and approximately 150–200cm of the bowel. The rest of the stomach and upper part of the small intestine remains in the body but is no longer used for food digestion.