Congenital cystic dilatation of the intrahepatic bile ducts (BILE DUCTS, INTRAHEPATIC). It consists of 2 types: simple Caroli disease is characterized by bile duct dilatation (ectasia) alone; and complex Caroli disease is characterized by bile duct dilatation with extensive hepatic fibrosis and portal hypertension (HYPERTENSION, PORTAL). Benign renal tubular ectasia is associated with both types of Caroli disease.