Illustration of gallstone disease, showing a group of stones (grey) forming in the gall bladder (green), with one solitary stone in the common bile duct (lower centre). Gallstone are classified by their composition into two main groups: cholesterol stones & bile pigment stones. The majority of gallstones remain in the gall bladder & produce no symptoms (silent" gallstones). Obstruction of the bile duct causes jaundice, bacterial infection (cholangitis) & formation of a liver abscess. Treatment is mainly by removal of the gall bladder (cholecystectomy), although dissolution is possible in some patient with cholesterol gallstones."