Liver disease is the catch-all term that is applied to any medical disorder affecting the liver and usually causing elevated blood levels of liver enzymes. It can be divided into both acute and chronic disease. Causes of acute liver disease include toxins (a number of drugs have been implicated in causing acute liver disease, including Tylenol, Rimadyl, Valium, tetracycline, sulfa drugs, and mushroom poisoning); also, hepatic lipidosis, trauma, heatstroke, and infections (canine infectious hepatitis). Causes of chronic liver disease include genetics, infections, toxins (anticonvulsants, Rimadyl), and idiopathic hepatitis.
Feline cholangiohepatitis is a common inflammatory liver disease in cats that may be associated with infection of bacteria from the intestines that ascend the bile ducts.
Certain breeds of dogs are prone to chronic hepatitis and cirrhosis (an end stage of liver disease in which liver tissue is replaced with fibrous tissue). Doberman Pinschers (especially females), American and English Cocker Spaniels, Bedlington Terriers, and West Highland White Terriers are the breeds associated with chronic liver disease and cirrhosis.
Clinical signs of liver disease include lack of appetite, vomiting, diarrhea, increased thirst, increased urination, lethargy, jaundice, and seizures. Liver disease is diagnosed by blood and urine tests, abdominal x-rays, and abdominal ultrasound. Liver biopsy is needed to determine the cause of liver disease.
A common liver disease in cats is hepatic lipidosis (fatty liver disease). This occurs in cats (and sometimes in dogs) as a result of starvation and weight loss (hepatic lipidosis can occur in cats who do not eat for as little as 72 hours). Depletion of certain nutrients (choline, carnitine, arginine) impairs metabolism of fat, resulting in fat deposition (rather than removal) from the liver.
PRINCIPAL NATURAL TREATMENTS FOR LIVER DISEASE IN PETS
Natural Diet—Dietary therapy is a mainstay of treating the pet with liver disease, as there are few conventional medications that actually treat liver disease. High quality and highly digestible carbohydrates are recommended to supply energy for the pet. Inferior types of carbs that are undigested are fermented by intestinal bacteria, which increase the bacteria in the colon. These bacteria then break down dietary proteins and produce extra ammonia, which is absorbed into the body and contributes to toxicity in pets with liver disease. Frequent feedings of high-quality, simple carbohydrates such as white rice and potatoes are recommended. Vegetables act as a source of complex carbohydrates and provide fiber; the fiber helps bind intestinal toxins and promotes bowel movements to remove these toxins (by-products of protein digestion and bacterial fermentation of undigested foods) from the body.
Proteins provided by the diet must be of high biological value to reduce the production of ammonia, a by-product of protein digestion. Most commercial foods contain proteins that are not of high biological value. (Many commercial foods may also contain excess vitamin A, copper, and bacterial endotoxins, all of which contribute to the clinical signs in pets with liver disease.) Unless your doctor recommends protein restriction (usually only needed by pets with encephalopathy, a condition producing neurological signs in pets with sever liver disease), normal amounts of protein should be fed, as the liver needs protein during repair.
Studies show that dogs with liver disease fed diets containing meat-based proteins have shorter survival times and more severe clinical signs than dogs with liver disease fed milk-based or soy-based protein diets. Cats require higher protein diets than dogs. While it may be more beneficial to cats to also feed them diets based on milk-based or soy-based proteins, most cats prefer meat-based diets. Cats fed milk-based or soy-based proteins must have supplemental taurine (100–200 mg/day), as milk has minimal taurine and soy has no taurine.
In cats, hepatic lipidosis is the most common liver disease and is secondary to starvation (often seen in overweight cats who go without eating for as little as three to five days). It is a secondary complication of anorexia and obesity rather than a true primary liver disease. Force-feeding cats to help heal the liver and correct the underlying problem is the treatment to hepatic lipidosis. This often requires tube feeding of special diets. When feasible, high-fat (approx. 30%) enteral diets containing milk-based or soy-based proteins are ideal for these cats; taurine supplementation of 150 mg/8 ounces of liquid diet is recommended.
Adding the amino acids arginine or citrulline to the diet may be indicated, as these amino acids accelerate the conversion of highly toxic ammonia to urea, reversing the clinical signs of toxicity that may occur in pets with liver disease. Glycine may decrease the toxicity that affects the kidneys when the chemotherapy drug cisplatin is administered.
Fat is used in the diet for energy. Even pets with fatty liver disease do well on diets containing 20 to 25 percent fat. Free fatty acids contribute to increased blood ammonia by interfering with ammonia metabolism. Dietary fats do not contribute to increased blood levels of free fatty acids; fasting or starvation will contribute to increased levels of free fatty acids. Therefore, pets with liver disease should have diets containing adequate amounts of fats and should receive frequent small feedings. Additionally, small frequent feedings reduce protein breakdown by the body (which can worsen clinical signs), improve glucose metabolism (preventing hypoglycemia), and decrease intestinal ammonia concentrations.
Increasing levels of vitamin A and copper can contribute to liver damage. Zinc supplementation may be of benefit as many pets with liver disease are deficient in zinc, and it can reduce copper absorption. Adding vitamins C, E, and K may be warranted.
Vitamin E protects against metabolism of lipids in cell membranes. Vitamin K is needed for proper blood clotting, which can be a problem in pets with severe liver disease. While dogs and cats can make vitamin C in the liver and do not normally require this vitamin, liver disease may decrease the amount of vitamin C. Supplementation with these vitamins under veterinary supervision may be helpful.
Milk thistle is well known for use in liver disease. Its silymarin content has been shown effective in treating liver disease. Milk thistle compounds are usually standardized to 70 to 80 percent silymarin. Milk thistle is one of the few herbs that have no real equivalent in the world of conventional medicine.
The active ingredients appear to be four substances known collectively as silymarin, of which the most potent is named silibinin. When injected intravenously, silibinin is one of the few known antidotes to poisoning by the deathcap mushroom. Animal studies suggest milk thistle extracts can also protect against many other poisonous substances, from toluene to the drug acetaminophen.
Silymarin appears to function by displacing toxins trying to bind to the liver as well as by causing the liver to regenerate more quickly. It may also scavenge free radicals and stabilize liver cell membranes. However, milk thistle is not effective in treating advanced liver cirrhosis, and only the intravenous form can counter mushroom poisoning.
Silymarin protects the liver as an antioxidant, by increasing glutathione levels, and by inhibiting the formation of damaging leukotrienes. Silymarin also stimulates the production of new liver cells, replacing the damaged cells.
Due to its liver support, milk thistle is often used anytime the pet becomes ill to support the liver. It can also be used anytime drugs are given to the pet that could be toxic to the liver, especially chemotherapy medicines, heartworm medications, and long-term use of other medications.
In people, treatment produces a modest improvement in symptoms of chronic liver disease. Liver enzymes as measured by blood tests frequently improve, and if a liver biopsy is performed, there may be improvements on the cellular level. Some studies have shown a reduction in death rate among those with serious liver disease.
A new form of silymarin, in which the compound is bound to phosphatidylcholine, has been shown to have greater bioavailability than unbound silymarin. It is best not to use milk thistle as a daily preventive supplement but rather reserve its use for conditions where the liver is under stress.
The standard dosage of milk thistle is 100 mg per 25 lb of weight, two to three times a day. In people, the best results are seen at higher doses (140 to 200 mg three times daily standardized to contain 70% silymarin); the bound form is dosed at 100 to 200 mg twice daily.
Do not use milk thistle in pregnant animals. Long-term use may alter blood liver enzymes. High doses may cause diarrhea.
Safety in young children, pregnant or nursing women and individuals with severe renal disease has not been established. Similar precautions in pets are probably warranted.
Other Natural Treatments
Other natural treatments include the nutrients choline, carnitine, and arginine. The herbs boswellia, burdock, chaparral, dandelion root, licorice, nettle, Oregon grape, red clover, turmeric, yellow dock and maitake mushrooms.
There is no specific treatment for liver disease in dogs and cats, unless a specific toxin is identified. Supportive care includes intravenous fluids and force-feeding. Force-feeding is the treatment of choice for cats. It usually requires feeding through a gastrotomy (stomach) tube for two to three months. Antibiotics and/or corticosteroids may be indicated, for example, for feline cholangiohepatitis.