Risk factors for cholangiocarcinoma

Cholangiocarcinoma is a rare malignancy with wide variation in incidence rates throughout the world. Approximately 10% of patients with cholangiocarcinoma are found to have an established risk factor such as infestation with liver flukes, primary sclerosing cholangitis, choledochal cysts, hepatolithiasis or cirrhosis. Obesity has recently been reported to increase the risk for extrahepatic cholangiocarcinoma. Standardized classification of anatomic tumor distribution and of risk factor definitions are necessary for accurate interpretation of conflicting study reports. 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 cholangiocarcinorna 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 cholangiocarcinorna was unusual, the association of obesity with the risk of developing cholangiocarcinoma persisted for all anatomic subsites.