Mass of crystallized substances that forms in the gallbladder .
The most common type occurs when the liver secretes bile with too much cholesterol to stay in solution. Liver damage, chronic gallbladder disease, or biliary-tract cancer may predispose one to stone formation. In the gallbladder, stones may cause inflammation or produce no symptoms. A stone obstructing the bile duct causes severe pain (biliary colic). Gallstones usually must be removed with the gallbladder or broken up with ultrasound . In some cases a stone can be treated by giving the patient bile salts, which help redissolve cholesterol. If the gallbladder must be removed, laparoscopy is the method of choice.