Portal vein internal diameter of 12mm belongs to widening. Mild fatty liver does not usually cause portal vein internal diameter to increase, only when fatty liver induces cirrhosis, portal vein widening can occur. The inner diameter of portal vein is usually 0.6 to 1 centimeter, so the inner diameter of portal vein 12mm belongs to enlargement. Mild fatty liver is usually caused by excessive accumulation of fat in liver cells, which may have no obvious symptoms or some patients may have symptoms such as abdominal distension and right upper abdominal pain, and generally does not cause portal vein widening, which can only occur when fatty liver induces cirrhosis. If the internal diameter of portal vein is slightly increased when the patient is in the state of inspiration during the measurement, the internal diameter of portal vein of 12mm in such cases is normal, but generally will not exceed 15mm, if it exceeds 15mm, it needs to be suspected that it is caused by splenic hyperfunction, cirrhosis and other disease factors. If the internal diameter of the portal vein is 12mm, it is recommended to go to the hospital and ask the doctor to make a judgment.