Ans. A: USG In Europe and USA 80% of the stones are cholesterol or mixed type. In Asia, 80% of the stones are pigment stones On the basis of their contents, gallstones can be subdivided into the two following types: Cholesterol stones are usually green, but are sometimes white or yellow in color. They are made primarily of cholesterol. Pigment stones are small, dark stones made of bilirubin and calcium salts that are found in bile. Risk factors for pigment stones include hemolytic anemia, cirrhosis, biliary tract infections, and hereditary blood cell disorders, such as sickle cell anemia and spherocytosis. Mixed stones-most of these are a mixture of cholesterol and calcium salts. Because of their calcium content, they can often be visualized radiographically. Cholesterol gallstones develop when bile contains too much cholesterol and not enough bile salts. Besides a high concentration of cholesterol, two other factors seem to be impoant in causing gallstones: The first factor is how often and how well the gallbladder contracts; incomplete and infrequent emptying of the gallbladder may cause the bile to become overconcentrated and contribute to gallstone formation. The second factor is the presence of proteins in the liver and bile that either promote or inhibit cholesterol crystallization into gallstones. Increased levels of the hormone estrogen as a result of pregnancy, hormone therapy, or the use of combined (estrogen-containing) forms of hormonal contraception, may increase cholesterol levels in bile and also decrease gallbladder movement, resulting in gallstone formation. It is most common for a person to have gall stones if (s)he falls under the four F's: Fat, Female, (nearing) Foy, Feile. A diagnosis of gallstone is based on the history and physical examination with confirmatory radiological studies like USG Cholesterol gallstones can sometimes be dissolved by oral ursodeoxycholic acid. Obstruction of the common bile duct with gallstones can sometimes be relieved by endoscopic retrograde sphincterotomy (ERS) following endoscopic retrograde cholangiopancreatography (ERCP).