Liver Failure in Horses
- Jul 28, 2011
Veterinarians often employ blood tests to detect liver-specific enzymes and metabolites in the bloodstream, which, if abnormally high, are indicative of liver disease and sometimes failure.
Photo: Anne M. Eberhardt/The Horse
You might be hard-pressed to find a horse owner who hasn't heard of commonplace equine ailments such as colic, arthritis, or laminitis. But a less common concern that might not always on owners' radars is liver failure. In fact, according to Thomas J. Divers, DVM, Dipl. ACVIM, ACVECC, professor and Chief of Large Animal Medicine at Cornell University, horses rarely experience liver failure. When they do, however, it's important to diagnose and treat them quickly and appropriately as this complex condition can be fatal. Divers presented on the topic at the 2011 Western Veterinary Conference, held Feb. 20-24 in Las Vegas, Nev.
The liver plays an important role in the equine digestive, endocrine, coagulation (clotting), and immune systems. Its primary function is detoxification, protein synthesis, and production of biochemicals necessary for digestion. The liver can typically still function adequately when it is partly damaged or diseased; however, a highly damaged liver can be a very serious problem.
Divers explained that horses and foals are most likely to develop liver damage or disease when they have a pre-existing septic, hypoxic (lacking oxygen), neoplastic (abnormal growths or tumors), toxic, or metabolic condition.
He added that the progression from liver disease to failure is rare, but causes of failure can include:
- Toxicity from alslike clover, Panicum grasses, or pyrrolizidine alkaloids (toxins found in weeds such as ragwort, fiddleneck, hound's tongue, and others);
- Cholangiohepatitis (inflammation and/or infection of the bile duct and liver tissue). Not all cases of cholangiohepatitis are infectious; they might also occur from toxic or immunologic causes;
- Tyzzer's disease (an acute, often fatal disease most commonly of foals caused by the bacterium Clostridium piliforme);
- Theiler's disease (also known as serum hepatitis);
- Chronic active hepatitis;
- Neoplasia (tumors);
- Hepatic lipidosis (a disorder involving deposition of fat in the liver);
- Biliary stones;
- Right dorsal colon displacement with obstruction of the bile ducts;
- Torsion (twisting) of the liver;
- Portal vein thrombosis (a blockage of the vein that leads to the liver); and
- Hyperammonemia (excess ammonia in the blood), which can also occur in horses without liver disease.
So how will you know if a horse is suffering liver failure? Divers explained there are several clinical signs of liver failure, and they tend to be specific to the cause.
The predominant signs of a horse experiencing acute (sudden) liver failure are likely neurologic deficits and jaundice. Horses suffering from chronic (ongoing) liver disease that is heading towards failure are likely to lose weight and have white areas of skin become sensitive to light. In both cases gastric impactions and bilateral laryngeal paralysis have been noted.
Liver failure caused mostly by abnormalities in the biliary system will present with marked jaundice, photosensitivity, and colic (often due to an obstruction in the bile duct and possible enlargement of the liver), Divers said. These horses do not commonly have neurologic deficits, he added.
Finally, he explained that some very specific causes of liver failure are accompanied by very specific clinical signs. Cholangiohepatitis, for example, will produce fever in horses; hepatic lipidosis will produce ventral edema (swelling); and right dorsal colon displacement will cause abdominal distention and abnormally tight colonic bands felt on rectal palpation.
Although the causes of liver failure and the signs it can present are somewhat complicated, diagnosic methods are relatively straightforward.
"Biochemical testing is imperative in the diagnosis of ... liver failure," Divers explained. "The results can be helpful in narrowing the differential diagnosis for the liver failure and, when evaluated over time, can help predict prognosis."
Divers explained that biochemical tests are used to detect liver-specific enzymes and metabolites in the bloodstream, which, if abnormally high, are indicative of liver disease and sometimes failure.
Divers said an ultrasound examination and a liver biopsy are the two most common tests used to identify the type of liver disease. He noted that ultrasound also can reveal a number of abnormalities indicative of liver disease. Performed in conjunction with the ultrasound, a biopsy can aid in determining the type, location, and duration of disease and might pinpoint infectious agents.
Treatment and Prognosis
The treatment of liver disease and failure typically depends on the cause, Divers explained, but most cases will receive supportive treatment with intravenous fluids, dextrose (sugars), frequent feeding of a low protein diet along with medical treatments to decrease intestinal ammonia production, vitamins, and potassium. In some cases of liver failure, depending on the severity, veterinarians might employ different and specific forms of therapy depending upon the cause. These treatments include other intravenous and oral medications and in some cases surgery.
Divers explained that the prognosis for liver failure depends on the cause, amount of fibrosis (scarring), and how the horse responds to treatment. Horses with Theiler's disease, for instance, either die or are euthanized within days of liver failure or respond rather quickly to treatments. Toxic causes of liver failure generally have a guarded prognosis, while hepatic lipidosis can have a good prognosis if treated properly. Divers added that if fibrosis on the liver is present, the prognosis declines.
"In many cases, a causative reason for liver disease and failure and horses cannot be determined," Divers said. "Some types of liver disease can be easily diagnosed after considering history, biochemical findings, ultrasound examination, and liver biopsy if needed. Treatment is often successful for many causes as long as fibrosis is not prominent."
About the Author
Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.
POLL: Mosquito-Borne Diseases