Non-widening of the internal diameter of the portal vein and common bile duct is generally a description of their status as normal on imaging. Normally, the portal vein and common bile duct internal diameters are not widened, and widening is an abnormality. The normal range of portal vein internal diameter is 6-10 mm, and normal physiologic factors may cause it to widen slightly; more than 13 mm is usually diagnosed as an abnormality, which is common in cirrhosis and portal hypertension. The normal range of internal diameter of common bile duct is 6~8mm; when the common bile duct is obstructed, the pressure inside the duct increases, which may lead to thickening or dilatation of the common bile duct, and the diameter can be more than 2cm, which is commonly seen in the stone of common bile duct and the tumor in the lower part of common bile duct, the tumor in the head of pancreas compresses the bile duct, and the tumor in the duodenal papilla blocks the opening of the common bile duct; and there is also a special case of congenital choledochal cyst, which is the birth of widening of common bile duct. Abnormalities of the portal vein and common bile duct are often indicative of more serious diseases, so it is advisable to have regular medical checkups for early detection and intervention, and to consult a doctor in case of uncomfortable symptoms.