As with any animal the horse's liver plays a key role in detoxifying the blood, regulating parts of the metabolic process, as well as storage of nutrients and synthesis of essential chemicals and proteins in the body. The liver is also very important in producing bile, which is necessary for proper digestion.
Liver diseases and disorders can occur due to injury, infections, disease, genetic conditions or even toxicity. Depending on the decrease in functioning of the liver the clinical signs of liver problems can range from a jaundiced or yellow appearance to the whites of the eyes to severe causes resulting in rapid death. In mild to moderate cases there will also be colic or digestive problems, swelling of the abdominal area and weight loss, and even central nervous system problems such as staggering, lack of coordination and muscle weakness due to a condition known as hepatic encephalopathy. Depending on the type of onset of the condition these symptoms may be very sudden or may develop slowly over time.
Acute or severe, quick onset liver disorders are most commonly associated with bacterial infections, toxicity and viruses or parasite infections. The same conditions can become chronic if they are not fully treated or if the horse is able to combat but not completely eradicate the cause of the liver problem. In some horses abscesses due to secondary infections from other diseases may cause chronic problems of the liver after the primary conditions is cured or treated.
In some cases foals are born with congenital liver malformations that become more pronounced as the horse ages. Shunts that cause blood to by-pass the liver and not be filtered or malformation or atrophy or the liver can affect the liver's ability to operate to the extent needed to keep the maturing foal healthy. Young foals may also be at risk for liver disorders due to infection by salmonella bacteria or trauma or injury to the liver at birth or shortly after they are born.
There are some known liver diseases that are problematic in different breeds of horses. Miniature horses and some of the cobby type of pony breeds are prone to a condition known as fatty liver or hepatic lipidosis. Usually these horses or ponies are very obese already and have other health issues that have contributed to the liver problem.
Fibrosing hepatitis is a chronic condition that occurs after the liver has been damaged by disease or trauma. The liver tissues become thick and fibrous and do not function properly, cutting down on the organ's ability to complete its role in metabolism. Typically this condition is seen in older horses.
Treatment of liver disorders and conditions is on a case-by-case basis. With parasites, viruses or infections treatment of the condition is often successful provided there is early diagnosis and treatment. In chronic conditions the success rate for treatment is less positive, but new options in drug therapies are increasing the success rate of treatment for even chronic liver disorders.