During digestion, bile flows from the liver through the hepatic duct into the common bile duct and empties into the duodenum, which is the first section of the small intestine. Between meals, the bile is not needed but it continues to flow from the liver into the common bile duct. It is kept out of the duodenum by a small, ringlike muscle called the sphincter of Oddi, which tightens around the opening. The fluid then is forced to flow into the gallbladder, where it is concentrated and stored until it is needed for digestion. This hormone is formed in the upper part of the small intestine.
Gallstones sometimes form within the concentrated bile.
These small, hard masses may become stuck in the common bile duct, causing severe pain. Doctors commonly treat gallstones by surgically removing the gallbladder. This operation once required a hospital stay of a week or more. Some gallstones can be dissolved by taking a medication. Others can be treated by using a device called a lithotripter.