Caroli disease, also known as congenital intrahepatic biliary duct dilatation, is a relatively rare congenital biliary tract disorder. 1, Caroli is divided into two types according to its tissue structure: simple type and periportal fibrosis type. (1) Simple type of intrahepatic bile duct dilatation: there is intrahepatic bile duct dilatation but normal color and texture of liver parenchyma, and there is only fibrous tissue hyperplasia in the dilated bile duct wall. It is not associated with cirrhosis and portal hypertension. About half of the cases are combined with renal cystic lesions or medullary spongy kidney. (2) Perivenous fibrosis type: In addition to segmental dilatation of bile ducts in the liver, it is often accompanied by congenital fibrosis of the liver, with extensive fibrous hyperplasia from the interstitial portal vein to the periportal lobules, which may even lead to cirrhosis and portal hypertension. 2.Typing according to the extent of lesions According to the extent of lesions, the disease is divided into two types: unilateral type, which is limited to one lobe or half of the liver, and bilateral type, which involves the left and right liver lobes. 3.Typing according to the number of lesions According to the number of lesions, it is divided into two types: single and multiple intrahepatic bile duct dilatation. The intrahepatic bile ducts at all levels can have round or shuttle-shaped cystic dilatation, with a diameter of 0.5-5 cm, and appear as beads or grapes, scattered in the liver lobe. Regarding the relationship between Caroli’s disease and bile duct carcinoma, a literature search revealed that there have been reports of Caroli’s disease combined with carcinoma of the biliary system in the past 20 years at home and abroad. However, a careful statistical analysis of this literature reveals that most of the reports are of biliary tract carcinoma in congenital biliary dilatation combined with intrahepatic bile duct dilatation. Although carcinoma of the biliary tract in Caroli’s disease has also been reported, there is no evidence to confirm that this disease has a high rate of carcinoma like congenital choledocholithiasis, with an incidence of 4% to 7% in adults. Treatment of this disease is difficult and the best treatment option for Caroli disease is still debated, and the prognosis for severe cases is often poor. Patients without biliary obstruction or cholangitis may be left untreated for observation and follow-up. Those with mild symptoms can be treated first by conservative methods. The basic treatment principle should be early diagnosis, prevention and treatment of cholangitis as the basic requirement.