The clinical signs of cholangiohepatitis vary depending on the severity of infection and the organism involved, and the signs
may be acute, subacute or chronic.1 Anorexia, weight loss, intermittent or persistent fever or colic are often associated with subacute or chronic cases. For
these horses, icterus, increased bilirubin and total bile acid concentrations as well as elevated liver enzyme activities
are also common. A swollen, soft, pale liver is indicative of acute cholangiohepatitis.
Davis notes that in severe cases, other findings include signs of hepatic failure such as hepatic encephalopathy, colic with
associated increases in hepatic enzyme activity, histopathologic evidence of cholangiohepatitis associated with large colon
displacements and ulcerative duodenitis in foals and yearling horses. "This suggests GI disease might be a predisposing factor,"
In addition to cholangiohepatitis, some horses also have cholelithiasis. "Horses get stones in their livers sometimes associated
with infections or from a dietary association—soft brown stones, and they're usually crushable," says Byars. "If they end
up going to surgery, the stones are crushed, so the surgeon doesn't have to remove them."
Horses don't have gallbladders, so when those channels are affected (i.e., plugged), they don't have residual bile storage.
"A lot of these horses are not jaundiced; many are functioning reasonably well," says Byars. "Most are not at a crisis, except
for a small percentage that Dr. Peek and Dr. Divers describe as being end-stage. It's kind of like a person who has the blahs—doesn't
feel consistently well."
The liver is the body's processing plant. "So, if the liver is having difficulties, energy level and the detoxification process
are being slowed," Byars says. "Metabolically, that would be compromising and can lead to varying clinical signs. Horses are
also unique in that they can be off feed for some other reason that has nothing to do with liver disease and develop icterus
called anorectic icterus. Their bilirubin will increase—not terribly, but way out of the normal range. So, for some of those horses that just don't
eat, they go back on feed, and then it goes away.
"The bottom line is to pull lab work," Byars says. "If you have a horse that's not doing well, you probably don't suspect
hepatitis or cholangiohepatitis. Within the blood work there are certain liver enzymes that are not only produced by the liver
but also are cleared by it. And there are some enzymes that are not produced in particularly great amounts by the liver but
are also cleared by it."
Gamma-glutamyltransferase (GGT) can be a marker found in horses that reflects suspicion of liver involvement, according to
Byars. Several published reports have found increased GGT activity in performances horses that have decreased performance
without apparent reason. "Many of those don't perform well, but they get better," Byars says. "Whether they had a cholangiohepatitis
or something similar, you'd never know unless the enzyme elevations continue to produce a predictable pattern or you do a
liver biopsy. Obviously, horses in training aren't candidates for liver biopsy."
The enzymes alkaline phosphatase (ALP) and GGT are cleared through the liver; GGT is also produced by the liver. "When those
two simultaneously increase, you begin to think of reduced bile flow," says Byars.
Liver enzymes such as lactate dehydrogenase (LDH) and aspartate transaminase (AST) are found in many parts of the body and
are, therefore, not liver-specific. "If you have elevated GGT activity by itself, you may suspect a clearance problem. If
you also have increased ALP, then you know the bile flow is reduced and most likely you have a cholangitis, and possibly cholelithiasis."