Biliary colic is a steady or intermittent ache in the upper abdomen, usually under the right side of the rib cage. It happens when something blocks the normal flow of bile from the gallbladder. Bile is a liquid that helps to digest fats. Under normal circumstances, bile is made in the liver and stored in the gallbladder. When you eat a meal, bile passes from the gallbladder through the cystic duct and the common bile duct into the small intestine, where it mixes with partially digested food.
Gallstones are the most common reason for biliary colic. If a gallstone blocks either of these ducts, the normal flow of bile into the intestine is disrupted. The muscle cells in the bile duct contract vigorously to try to move the stone, causing the pain of biliary colic. A stricture of the bile duct or a tumor also can block bile flow and cause biliary colic.