The stomach leads to the first part of the small intestine, also called the duodenum. The common bile duct carries bile from the liver to the duodenum, and enters the duodenum a few centimeters beyond the stomach.
Gallstones usually form in the gallbladder. Gallstones sometimes pass from the gallbladder into the common bile duct, and block the flow of bile into the duodenum. This can result in serious illness. Additionally, tumors of the pancreas and duodenum can block the bile duct, also preventing the flow of bile into the duodenum.
If gallstones are present in the common bile duct, the surgeon can perform a sphincterotomy. A small incision is made through the endoscope, which enlarges the opening of the common bile duct into the duodenum. The stones can then pass through.
If a tumor is present and constricting the bile duct, a plastic or metal stent can be placed into the bile duct, thus holding it open, and allowing bile to pass through.