gallstone

n.

a hard mass composed of bile pigments, cholesterol, and calcium salts, in varying proportions, that can form in the gall bladder. The formation of gallstones (cholelithiasis) occurs when the physical characteristics of bile alter so that cholesterol is less soluble, though chronic inflammation of the gall bladder (see cholecystitis) or diminished contractility may also be a contributory factor. Gallstones may exist for many years without causing symptoms. However, they may cause severe pain (see biliary colic) or they may pass into the common bile duct and cause obstructive jaundice or cholangitis. Gallstones are usually diagnosed by ultrasonography, but those containing calcium may be seen on a plain X-ray (opaque stones). Cholelithiasis is usually treated by surgical removal of the gall bladder (see cholecystectomy) or by removing the stones themselves, which can be either dissolved using bile salts given by mouth or shattered by ultrasound waves. There is no need for treatment if the stones are causing no symptoms.