GALLSTONE

concretion composed of crystalline substances (usually cholesterol, bile pigments, and calcium salts) imbedded in a small amount of protein material formed most often in the gallbladder. The most common type of gallstone consists principally of cholesterol. Its occurrence has been linked to secretion by the liver of bile that is saturated or supersaturated with cholesterol and contains abnormally low levels of bile salts and lecithin, which in normal bile are present in sufficient quantities to keep cholesterol in solution. Predisposing factors to the development of gallstones (cholelithiasis) are inflammation and stagnation resulting from liver damage, chronic gallbladder disease, or cancer of the biliary tract. Stones located in the gallbladder may produce no clinical symptoms, or they may set up an inflammatory process, producing acute inflammation of the gallbladder (cholecystitis, q.v.). When a stone becomes lodged in the bile ducts, obstruction leads to increased pressure above the site of blockage, resulting in the severe pain known as biliary colic. Gallstones sometimes pass into the intestines spontaneously, but in most instances they must be removed by surgery or dissolved by ultrasonic therapy. The gallbladder itself is sometimes removed during surgery to prevent further stone production. In some cases, cholelithiasis can be treated medically by feeding the patient bile salts to dissolve gallstones and reduce the concentration of cholesterol in the bile.