Risk factors for cholangiocarcinoma.

Cholangiocarcinoma occurs with a varying frequency in different areas of the world. Some of the variations in incidence rates can be explained by the distribution of risk factors in different geographic regions and ethnic groups. Several accepted risk factors for cholangiocarcinoma include infestation with liver flukes, primary sclerosing cholangitis, hepatolithiasis, choledochal cysts, cirrhosis, and infusion of certain chemical agents. Approximately, 90% of patients diagnosed with cholangiocarcinoma do not have a recognized risk factor for the malignancy. The study by Ahrens et al. [16] finds that obesity and gallstones are risk factors for developing extrahepatic cholangiocarcinoma in men patients. Obesity was found to have a 'dose-effect' relationship with the strength of statistical association. No significant association was reported for tobacco or alcohol use, hepatitis, cirrhosis, diabetes, or inflammatory bowel disease. Although the author's definition of extrahepatic cholangiocarcinoma was unusual, the association of obesity with the risk of developing cholangiocarcinoma persisted for all anatomic subsites.