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Fat Cats are Predisposed to Liver Problems

Pet Column for the week of February 21, 2005

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Kim Marie Labak
Information Specialist

If a cat, especially an overweight cat, stops eating, it can suffer serious liver problems. According to Dr. Marcella Ridgway, veterinary internist at the University of Illinois Veterinary Teaching Hospital in Urbana, cats are extremely dependent upon having protein in their diets. Unlike many species, cats cannot adequately synthesize their own protein from other building blocks.

If a cat is not taking in enough protein, it will start breaking down proteins from its body, including important muscle and liver proteins. At the same time, the body is starving for energy, so it mobilizes fat stores for calories, and carries this fat to the liver for processing.

Normally, the liver would metabolize these fats to use them for energy, store them, or secrete them through bile. If the liver is missing some of the proteins needed for fat metabolism, all a liver cell can do is store the fat. The fat builds up inside the cells, a condition called hepatic lipidosis, or "fatty liver,"and the cells swell, pinching off bile ducts. Bile, with all its waste products, cannot empty from the liver into the intestine as it normally does, and the cat becomes jaundiced.

These changes in the liver occur within 36 hours of not eating. Since the liver cannot metabolize the fat for energy, the cat suffers further starvation, setting up a vicious cycle of fat mobilization and liver damage.

Although this buildup of fat inside liver cells is often associated with diseases that cause decreased appetite, or metabolic disorders such as diabetes, Dr. Ridgway says she also sees cases that are idiopathic, or have no identifiable underlying cause.

To diagnose fatty liver, a sample of liver must be obtained. The "gold standard" test is liver biopsy, or removal of a small chunk of liver tissue for microscopic examination, but this test is invasive and often unnecessary; taking a sample of liver cells with a needle is much less invasive and usually adequate to make the diagnosis. An abdominal ultrasound may show a change in liver size or consistency, indicating fat buildup. Jaundice, or yellowing of the whites of eyes, ears, and gums, is one sign of liver disease that can occur in cats with fatty liver.

To treat the problem, Dr. Ridgway explains, the causative condition must be treated and the cat should be fed high-protein, high-carbohydrate food for energy and to replace lost protein. Usually with liver disease, veterinarians limit protein intake, but fatty liver is an exception, since liver proteins need to be replaced.

This treatment plan is not as simple as it sounds, since cats with fatty liver usually don't feel well enough to eat on their own. Cats with this condition require a lot of calories, which means frequent feedings, at least four times a day. Force-feeding can ruin the bond between cat and owner, and can actually cause cats to develop an aversion to food, exacerbating the problem.

Since patients may need special feedings for several weeks or more, a sensible treatment is endoscopic or surgical placement of a feeding tube, according to Dr. Ridgway. A feeding tube may go through the skin of the neck into the esophagus, or through the body wall into the stomach. This way, soft food can be pushed through the tube into the stomach.

Along with treating the liver problem and its initial cause (if there is one), veterinarians also have to treat problems resulting from the liver problem, and these can range from infections to neurological problems.

Fortunately, the liver swelling and fat buildup are usually reversible, and most patients respond well to tube-feeding treatment. Recovery time varies; some cats may improve within a week, while it may be months before others start eating on their own.

Thin cats that stop eating can also suffer liver damage, but fatty liver develops more slowly or to a lesser degree. The fatter the cat, the more fat there is available to be mobilized and moved to the liver, where it will build up in liver cells if the cat is protein-deficient.

"Fatty liver is just one reason it's so important to keep cats at a healthy weight," says Dr. Ridgway. She also recommends keeping an eye on your cats food intake and being aware that cats often stop eating in new situations, such as during boarding or after moving to a new home. Overweight cats should not be put on low-calorie diets without veterinary guidance, and owners should contact their veterinarians about any cat that hasn't eaten for more than a day.

For more information about fatty liver disease or maintaining a healthy weight for your cat, consult your veterinarian.