The causes of dilated intrahepatic bile ducts are as follows: 1, congenital dilatation called common bile duct cyst; 2, dilated intrahepatic bile ducts caused by biliary obstruction, stones causing biliary obstruction and dilated intrahepatic bile ducts; if there are tumors in the lower segment, such as hilar cholangiocarcinoma, tumors of the middle and lower bile ducts, or even tumors of the head of the pancreas, which compress the common bile ducts causing biliary obstruction and dilated intrahepatic bile ducts; 3, previous bile-intestinal anastomosis surgery, intestinal gas entering the bile duct, causing gas accumulation in the bile duct of gallbladder and even dilated intrahepatic bile duct manifestations. According to the cause, combined with imaging examination or even enhanced examination to exclude stones, tumors, obstruction, whether there is congenital dilatation of the common bile duct, detailed medical history, reference imaging, and clarify whether the patient has previously undergone the corresponding surgery.