Clements O, et al. - Given that cholangiocarcinoma (CCA) is a cancer arising in the bile ducts inside (intrahepatic CCA, iCCA) and connected to the liver (extrahepatic, eCCA), researchers performed a comprehensive meta-analysis of risk factors for iCCA and eCCA, from Eastern and Western world studies. To identify potential risk factors for iCCA and eCCA, a literature search of case-control studies was performed. Biliary cysts and stones, cirrhosis, hepatitis B and hepatitis C were the strongest risk factors for both iCCA and eCCA. Choledochal cysts with pooled OR of 26.71 and 34.94, respectively, inferred the greatest risk of both iCCA and eCCA. No significant connections between hypertension and obesity for either iCCA or eCCA were observed. There was a difference in the association of hepatitis B with iCCA compared with the Eastern and Western populations.