(See also Overview of Blood Vessel Disorders of the Liver.)
Ischemic hepatitis is damage throughout the liver caused by an inadequate blood or oxygen supply.
In ischemic hepatitis, liver cells are damaged or die because the liver does not receive enough blood or oxygen.
Ischemic hepatitis differs from other types of hepatitis. Usually, “hepatitis” implies inflammation of the liver, which can have many causes, most commonly a virus (as in hepatitis A or B). However, in ischemic hepatitis, the liver is not inflamed. Rather, liver cell death (necrosis) occurs. The term hepatitis is used because technically, it refers to any disorder in which liver enzymes called aminotransferases leak from damaged liver cells into the blood.
Ischemic hepatitis develops when the liver’s requirements for blood, oxygen, or both are not being met.
Decreased blood flow throughout the body is the most common cause for such unmet needs. Blood flow may be decreased by the following:
Decreased oxygen levels in the body, as may result from prolonged, severe respiratory disorders, can also cause ischemic hepatitis.
An increased need for oxygen and blood, as occurs during a severe bodywide infection (sepsis), can contribute to ischemic hepatitis.
Blocked blood vessels can cause hepatic ischemia but only when both the hepatic artery and the portal vein are narrowed or blocked. Ischemia does not develop when only one of these blood vessels is narrowed or blocked because the liver receives blood from both the hepatic artery and portal vein, and the blood vessel that is not blocked continues to supply the liver with blood.
The most common cause of blocked blood vessels is a blood clot. (Blockage by a blood clot is called thrombosis.) Blood clots in the hepatic artery can have many causes, such as the following:
Injury of blood vessels (as occurs during liver transplantation surgery)
A bulge (aneurysm) in the hepatic artery
Inflammation of the artery (vasculitis)
Use of cocaine (causing spasm of the artery)
Tumors, certain medical procedures, or heart infections (endocarditis) that cause emboli—clumps of material, such as a piece of fatty material or blood clot on the wall of an artery—to break off and travel through the bloodstream and become lodged in a blood vessel
Disorders that make blood more likely to clot (blood clotting disorders) can cause blockages in the hepatic artery or portal vein. These disorders may be inherited or acquired.
Doctors suspect ischemic hepatitis when results of liver function tests (done to determine how well the liver is functioning and whether it is damaged) and/or blood clotting tests are abnormal in people who have a condition that can cause the disorder.
If doctors suspect ischemic hepatitis, they look for a cause. For example, they may do imaging tests to check for a blockage in the hepatic artery. These imaging tests include ultrasonography, magnetic resonance imaging (MRI) of blood vessels (magnetic resonance angiography), and arteriography, which involves taking x-rays after a radiopaque contrast agent (which is visible on x-rays) is injected into an artery.