An unusual anomalous intrahepatic connection between the left portal vein and internal mammary veins

Persistent embryonic portal vessels such as the umbilical vein or ductus venosus are occasionally encountered in the adult on ultrasound examination of the liver. These vessels must be identified and distinguished from the normal intrahepatic portal and hepatic veins. Recently, we have found another vein that, like the ductus venosus and persistent umbilical vein, is also a large intrahepatic portal vessel that is not a normal component of the hepatic vasculature. This anomalous vein originated from the left portal vein and traversed the liver parenchyma without branching to reach the anterior‐superior liver margin, serving as an intrahepatic portal‐systemic shunt by directly connecting the left portal vein and the internal mammary veins.