A hepatic vein is any of the veins that carry oxygen depleted blood out of the liver and into the inferior vena cava. The term vein refers to a blood vessel that transports blood back to the heart, in contrast to an artery, which carries blood away from the heart. The term hepatic relates to the liver.
The group of hepatic veins meets with the inferior vena cava at the posterior, or back, side of the liver. The vena cava is a major blood vessel that, in turn, transports the blood to the right atrium of the heart, where the blood may begin the process of becoming re-oxygenated.
Blood transported through a hepatic vein includes the blood that was used to feed the liver as well as blood from most other abdominal organs. This is because the liver functions as a cleaning station on the blood’s route back to the heart to get re-oxygenated. A phagocytic, or cell killing, system is set up in the liver to kill bacteria that may have entered the blood, especially through the intestines, and to get rid of dead or damaged blood cells. The liver can also store and release large amounts of blood in order to control the volume of blood being circulated through the body at any given time. Because it receives so much blood, the liver is a very vascular organ, or an organ in high possession of blood vessels.
The liver receives deoxygenated blood from other organs through hepatic portal veins and oxygenated blood to feed itself through the hepatic artery. At the terminal, or end, branches of the hepatic portal veins and the hepatic artery, the arterial and venous blood dumps together into the sinusoids which, in turn, empty into central veins located in each lobule. Sinusoids are specialized blood vessels with fenestrations, or small gaps between cells, to increase permeability for plasma and damaged cells to leave the blood stream. Each lobule has its own central vein that collects the blood from the sinusoids and passes it on to the hepatic vein groups.
Hepatic veins are divided into two groups, upper and lower, based on where the veins emerge out of the liver. The lower group emerges from the right lobe and the caudate lobe of the liver and may vary in number from person to person. The upper group emerges from the quadrate lobe and left lobe at the posterior side of the liver. There are usually three hepatic veins in the upper group, and they tend to be larger than veins of the upper group.
Budd-Chiari syndrome occurs when a hepatic vein outflow is blocked by an obstruction in a hepatic vein, the inferior vena cava, or the right atrium. This is commonly caused by a clot in the hepatic vein, especially in the global west, but it can also be caused by congenital or developmental defects, or unknown causes. Symptoms vary depending on whether the obstruction appears suddenly, wherein patients exhibit pain and signs of liver failure, or whether it occurs gradually, wherein patients may experience no pain but begin to show signs of liver failure as time passes. Common symptoms may be enlarged liver, raised liver enzymes, ascites, abdominal pain, jaundice, and, in advanced cases, cirrhosis. Treatment options include anticoagulants, sodium restriction, diuretics, surgical shunts, angioplasty, and liver transplant in an emergency or last resort situation.