Among the many vitally important roles performed by the feline liver is its contribution to the digestion of the food that a cat routinely consumes. This digestive process relies substantially on the liver’s efficient manufacture and secretion of bile, a potent, greenish-brown fluid that travels from the liver via the biliary system (an elaborate network of minuscule channels called biliary ducts) to the gall bladder. The bile is then stored in the gall bladder—a small balloon-like sac—until it is called upon to go to work in the intestinal tract. In response to hormonal signals, the gall bladder contracts and expels the bile through a tube (the common bile duct) into the small intestine, where it performs such necessary digestive processes as the breaking down of dietary fats so that they can be absorbed into a cat’s body and the processing of harmful toxins so that they are unable to be absorbed.
Among the most common causes of feline liver disease is cholangiohepatitis, a condition marked by inflammation of both the liver and the biliary system. This condition and hepatic lipidosis (fatty liver) combined account for perhaps two-thirds of all feline liver disorders treated at the typical cat clinic or veterinary hospital.
The inflammation can have two sources, notes Richard Goldstein, DVM, an associate professor of small animal medicine at Cornell University’s College of Veterinary Medicine. “One of the causes,” he points out, “is bacterial infection, probably initiating in a nearby area of a cat’s gut—the pancreas or small intestine, for example—and then traveling up the biliary tract. This tends to cause inflammation of neutrophilic cells, which the body recruits to fight bacteria.” This form of infection—referred to as suppurative (pus-forming)—tends to respond positively to antibiotic therapy, says Dr. Goldstein.
The other condition, which is more common, is an immune-mediated phenomenon affecting cells called lymphocytes. These cases (nonsuppuritive) tend not to respond to antibiotics, according to Dr. Goldstein. “So we will usually treat this type of cholangiohepatitis with immunosuppressive drugs, such as steroids,” he points out.
In either case, the inflammation and accompanying swelling interfere with the proper flow of bile, which results in its retention within the liver and biliary ducts. And because bile is a caustic digestive fluid, it can cause significant tissue damage when its normally fluent passage from the liver is impeded. The typical signs of cholangeohepatitis include loss of appetite, fever, vomiting, and jaundice (which can cause the white portions of the eye to appear yellow in color).
Because these clinical signs are similar to those associated with other serious liver disorders—such as liver cancer, feline infectious peritonitis and hepatic lipidosis—a variety of elaborate diagnostic tests may be needed in order to reach a definitive diagnosis of cholangeohepatitis. In addition to a complete blood count, blood chemistry analysis, and urinalysis, these tests may include abdominal x-rays and ultrasound; analysis of bile acids; and a test to determine the blood’s clotting ability. In some cases, exploratory abdominal surgery will be done to examine the liver and gall bladder. And if a tentative diagnosis of cholangeohepatitis is reached, a liver biopsy may be performed in order to confirm that diagnosis. A liver biopsy will also differentiate between the types of cholangiohepatitis, an important point since treatments vary depending upon the type of cholangiohepatitis diagnosed.
In general, the prognosis for feline cholangiohepatitis is unpredictable. If diagnosed at an early stage of the disease, some cats with the suppurative form of the disorder may respond well to antibiotic therapy and eventually return to normal. And long-term remission is possible in cats that are effectively treated for the nonsuppurative type. The prognosis is poor, however, for cats that are diagnosed with either type of cholangiohepatitis when it has already reached an advanced stage. Advanced cholangiohepatitis can progress to biliary cirrhosis, in which vitally important bile duct tissue is replaced by tough connective tissue. Although this process is regarded as the final stage of severe cholangiohepatitis, it is infrequently observed because seriously affected cats and those in which diagnosis has been delayed rarely survive long enough for it to develop. Prompt treatment will maximize the chance that treatment will be successful.