Epidemiology, pathogenesis, and classification of biliary stones (common bile duct and intrahepatic)

Gallstones are common in Western countries and Japan. Most gallstones are found in the gallbladder, but they sometimes pass through the cystic duct into extrahepatic and/or intrahepatic bile ducts to become bile-duct stones, causing conditions known as choledocholithiasis and hepatolithiasis. Some 10–15% of gallstone patients concomitantly suffer from bile-duct stones. Bile-duct stones can also be formed in the absence of gallbladder stones, and such primary bile-duct stones are more common in East Asian countries than in the Western world. Thus pathogenesis of primary and secondary bile-duct stones is unlikely to be similar. Furthermore, the gallbladder stones are primarily cholesterol or black-pigment stones, whereas most bile-duct stones are brown-pigment stones (calcium bilirubin stones). Thus, epidemiology, pathogenesis and classification of biliary stones are very likely to differ according to stone location (intrahepatic and/or extrahepatic bile duct).