Biliary colic is usually caused by spasm of the smooth muscle of the wall of the gallbladder in an attempt to expel a gallstone. Afferent nerve fibers ascend through the celiac plexus and the greater splanchnic nerves to the thoracic segments of the spinal cord.
Referred pain is felt in the right upper quadrant or the epigastrium (T7, 8, and 9 dermatomes). Obstruction of the biliary ducts with a gallstone or by compression by a tumor of the pancreas results in backup of bile in the ducts and development of jaundice. The impaction of a stone in the ampulla of Vater may result in the passage of infected bile into the pancreatic duct, producing pancreatitis. The anatomic arrangement of the terminal part of the bile duct and the main pancreatic duct is subject to considerable variation.
The type of duct system present determines whether infected bile is likely to enter the pancreatic duct. Gallstones have been known to ulcerate through the gallbladder wall into the transverse colon or the duodenum. In the former case, they are passed naturally per the rectum, but in the latter case, they may be held up at the ileocecal junction, producing intestinal obstruction.