Cholangiohepatitis in Horses

When early 2011 Kentucky Derby favorite Uncle Mo was scratched from the field just a few days before the race, many horse racing enthusiasts were left scratching their heads. His connections said the colt had a gastrointestinal tract infection; However no further diagnosis had been reached despite continued veterinary examination. Finally, an answer came several weeks after Uncle Mo's Derby scratch: Veterinarians diagnosed the colt with cholangiohepatits, a relatively rare condition in horses.

Essentially, cholangiohepatitis (CH) is an inflammation of the bile system (cholangitis) and liver (hepatitis). There is no particular breed or discipline predilection for developing CH.

Uncle Mo at WinStar Farm

Uncle Mo (photo taken June 6) is recovering well from a case of cholangiohepatitis at WinStar Farm in Versailles, Ky. (VIDEO)

According to one of Uncle Mo's attending veterinarians Bill Bernard, DVM, MS, Dipl. ACVIM, of Lexington Equine Surgery and Sports Medicine in Lexington, Ky., CH can have multiple causes including:

  • Obstructions of the common bile duct (that) occur from bile stones (like gall stones in humans, but horses don't have gall bladders), sludged bile, or from an abscess or tumor;
  • Chronic large colon displacement or stasis (lack of motility) in the duodenum (part of the small intestine) that contributes to bile stasis and sludge;
  • Viral or bacterial infections of the biliary tract that elicit inflammation; and
  • Other causes such as immune-mediated triggers, toxic plants, or pharmaceuticals (such as NSAIDs), which can induce inflammation in the biliary tract.

Since the liver is near the bile ducts, the liver cells become inflamed as well.

Anything a horse ingests can have a physiologic effect, so Bernard recommended that horse owners carefully consider their use of supplements, for example, stressing, "Supplements are not always necessary and may not even be good for the horses."

Typical clinical signs of CH aren't definitive. Bernard explained that an affected horse experiences gradual weight loss, acts depressed, and isn't as interested in physical activity as usual. One blood test that evaluates GGT (gamma glutamyl transferase, a liver enzyme) levels is an indicator of a problem with the biliary tract and/or liver if it shows elevated enzyme levels. However, GGT levels are slow to elevate and even slower to return to normal, making it hard to pinpoint where the horse is in the course of disease.

Additionally, Bernard said it's not uncommon to see hard-exercising racehorses with elevated GGT yet without any clinical problem. But, he continued, "The combination of a horse losing weight and not acting himself along with a markedly elevated GGT prompts additional investigation."

Veterinarians often employ an ultrasound of the biliary tract and liver as a noninvasive diagnostic approach.

"With recent or past obstruction in the common bile duct," explained Bernard, "we see dilation of this structure on ultrasound. The absence of dilation rules out a mechanical obstruction as cause of CH."

If ultrasound doesn't yield a diagnosis, the next approach is to obtain a liver biopsy, the procedure that eventually led to Uncle Mo's diagnosis.

Bernard explained that cholangiohepatitis is treatable, and most horses recover completely. In many horses disease resolves on its own with elimination of the inciting cause, such as toxic plants, drugs, or underlying intestinal disease. In some cases antibiotics are necessary to defeat a bacterial infection.

One concern for a CH patient, however, is progression of the disease to chronic active hepatitis, in which affected horses experience recurrence of acute bouts. But prompt diagnosis and appropriate care of a CH-affected horse can usually lead to a favorable outcome.

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her recent book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care (available at or by calling 800/582-5604). She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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