The liver receives the oxygen and nutrients it needs in blood that comes from two large blood vessels:
The portal vein provides about two thirds of the blood. This blood contains oxygen and many nutrients brought to the liver from the intestines for processing. The hepatic artery provides the remaining one third of blood. This oxygen-rich blood comes from the heart and provides the liver with about half of its oxygen supply. Receiving blood from two blood vessels helps protect the liver: If one of these blood vessels is damaged, the liver can often continue to function because it receives oxygen and nutrients from the other blood supply.
Blood leaves the liver through the hepatic veins. This blood is a mixture of blood from the hepatic artery and from the portal vein. The hepatic veins carry blood to the inferior vena cava—the largest vein in the body—which then carries blood from the abdomen and lower parts of the body to the right side of the heart.
Blood vessel (vascular) disorders of the liver usually result from inadequate blood flow—whether into or out of the liver. If the problem is blood flow out of the liver, blood backs up in the liver, causing congestion which can result in an enlarged liver. In either case, liver cells do not receive enough blood (called ischemia) and thus are deprived of oxygen and nutrients. In ischemic cholangiopathy, it is the bile ducts that do not receive enough blood.
Inadequate blood flow—into or out of the liver—may result from heart failure or disorders that make blood more likely to clot (clotting disorders). In clotting disorders, a clot may block the portal vein or a hepatic vein, slowing or blocking blood flow. Disorders with blockages in blood flow include
Budd-Chiari syndrome, which results when blood clots block blood flow from the liver
Portal vein thrombosis, which is a blockage or narrowing of the portal vein (the blood vessel that brings blood to the liver from the intestines) by a blood clot
Sinusoidal obstruction syndrome (previously called veno-occlusive disease), which arises when very small blood vessels within the liver are blocked