The hepatic veins carry oxygen-depleted blood from the liver to the inferior vena cava. They also transport blood that has been drained from the colon, pancreas, small intestine, and the stomach, and cleaned by the liver.
These veins originate from the core vein of the liver lobule, but they do not have any valves. They can be segregated into the lower group and the upper group veins.
The lower group veins originate from the lower parts of the right or caudate lobe. They are smaller in size than the upper group veins and vary in number from person to person. The upper group usually consists of three large veins that originate from the backside of the liver and drain the right, middle, and left lobes of the liver.
The oxygen-depleted blood from these veins empty into the inferior vena cava. From here, the blood is delivered back to the heart, where the re-oxygenation process of the blood takes place. In that respect, the liver performs the role of a filtering organ for blood that is on its way back to the heart.
Any impediment in the outflow of blood from the hepatic veins may result in a serious condition known as Budd-Chiari syndrome, which can cause liver damage.