Equine liver disease in the field. Part 1: approach

Liver disease is commonly encountered in adult horses and reaching an early diagnosis is key to ensuring a successful outcome. However, the prevalence of subclinical disease combined with a lack of pathognomic clinical signs make recognition challenging, and disease is oft en advanced by the time a diagnosis is made. In the first of two articles we provide an overview of the approach to liver disease in the field. Part 2 will focus specifically on causes and management of liver disease in adult horses.

The equine liver comprises 1.5% of body weight (Dyce et al, 2002) and contains up to 10% of the total blood volume at any one time. It has multiple functions including metabolism of proteins, carbohydrates and lipids; production of coagulation factors, plasma proteins and acute phase proteins; synthesis of vitamin C and storage of other vitamins; elimination of by-products (including ammonia and bilirubin); detoxification; phagocytosis; and drug metabolism by P450 enzymes. A close connection with the gastrointestinal tract via the hepatic portal vein means that the liver is regularly exposed to enteric-derived insults.