Risk factors

Although most patients present without any known risk factors evident, a number of risk factors for the development of cholangiocarcinoma have been described; in the Western world, the most common of these is primary sclerosing cholangitis (PSC), an inflammatory disease of the bile ducts which is in turn closely associated with ulcerative colitis (UC).^[10] Epidemiologic studies have suggested that the lifetime risk of developing cholangiocarcinoma for a person with PSC is 10%–15%,^[11] although autopsy series have found rates as high as 30% in this population.^[12] The mechanism by which PSC increases the risk of cholangiocarcinoma is not well understood.

Certain parasitic liver diseases may be risk factors as well. Colonization with the liver flukes Opisthorchis viverrini (found in Thailand, Laos, and Malaysia) or Clonorchis sinensis (found in Japan, Korea, and Vietnam) has been associated with the development of cholangiocarcinoma.^[13][14][15] Patients with chronic liver disease, whether in the form of viral hepatitis (e.g. hepatitis B or C),^[16][17][18] alcoholic liver disease, or cirrhosis from other causes, are at increased risk of cholangiocarcinoma.^[19][20] HIV infection was also identified in one study as a potential risk factor for cholangiocarcinoma, although it was unclear whether HIV itself or correlated factors (e.g. hepatitis C infection) were responsible for the association.^[19]

Congenital liver abnormalities, such as Caroli's syndrome or choledochal cysts, have been associated with an approximately 15% lifetime risk of developing cholangiocarcinoma.^[21][22] The rare inherited disorders Lynch syndrome II and biliary papillomatosis are associated with cholangiocarcinoma.^[23][24] The presence of gallstones (cholelithiasis) is not clearly associated with cholangiocarcinoma. However, intrahepatic stones (so-called hepatolithiasis), which are rare in the West but common in parts of Asia, have been strongly associated with cholangiocarcinoma.^[25][26][27] Exposure to Thorotrast, a form of thorium dioxide which was used as a radiologic contrast medium, has been linked to the development of cholangiocarcinoma as late as 30–40 years after exposure; Thorotrast was banned in the United States in the 1950s due to its carcinogenicity.^[28][29]