Liver Disease
The liver is an accessory gland of the digestive system and is the largest gland in the horse’s body. Like other species the liver of the horse has a bile duct that carries bile into the small intestine, however, a key difference in horses compared to other animals is that they don’t have a gall bladder to store bile. Three quarters of the blood that goes to the liver comes from the intestines, via the portal vein, containing products of the food that has been digested. The other quarter of the blood supply comes from the main body blood supply, via the hepatic artery, and provides the liver with the oxygen and nourishment that is required. All blood leaves the liver via the hepatic artery into the main circulation heading back to the heart. The liver is, therefore, acting as a filter to clean the blood from the intestines before it is released into the circulation.
Liver functions
The liver takes up sugar and stores it as glycogen to then be turned back into sugar and released if required. The liver also stores protein, fat and vitamins. The liver is able to protect the body against harmful substances by converting them into harmless ones. Examples of this include converting drugs so that they can be excreted in the urine and also prevents ammonia accumulating, which is toxic. The liver produces blood proteins and substances necessary for clotting blood. The liver produces bile which it then passes into the small intestine. Bile is a waste product but before it is excreted in the horse’s droppings aids in the digestion of fat.
Signs of liver disease
The signs of liver disease include jaundice (yellowing of the mucus membranes), weight loss, diarrhoea, fluid accumulation on the legs, chest and abdomen, neurological signs (circling, staggering and walking into objects) and occasionally fever.
Diagnosis of liver disease
Blood tests can be carried out to assess liver function in order to make a diagnosis of liver disease, however, often a sample of liver tissue is required (biopsy) to gain more information as to what is causing the liver disease.