The liver is a large abdominal organ that performs many vital functions. Liver failure implies that these functions are lost or lessened, which can happen suddenly or recently (acute) or occur over a longer period of time (chronic).

Toxins that affect the liver must be considered as a cause of liver failure and acute hepatitis. These include iron toxicosis, amanitins Amanita spp mushrooms, cocklebur, Alsike Clover, and Cyanobacteria or Blue-Green Algae. Liver failure can also be caused by ingestion of certain weeds. The most notable of these are the pyrrolizidine alkaloid producing plants. Another poorly understood condition that causes liver failure is Serum Hepatitis (Theiler's Disease).

Photosensitization occurs in chronic liver failure because the diseased liver cannot clear certain plant pigments from the blood. These pigments react with sunlight in pink skin to cause peeling and crusting of pink-skinned areas.

The liver makes the clotting factors (proteins critical to normal clotting of blood). In liver failure, these become deficient and a horse may bleed abnormally.

The liver creates albumin, a protein that "keeps blood in the vessels." In liver failure, albumin is reduced and swelling occurs in sheath, limbs and underbelly.

In the late stages of liver failure, we often see signs of brain disease. This occurs because of metabolic waste products become elevated in the blood because the poorly functioning liver cannot clear them.

Treatment for liver disease depends on treatment and removal of the underlying cause. Beyond that, treatment is supportive nursing care. Longer term management of horses in liver failure involves special feeding.