The early signs of liver disease are nonspecific. They include loss of appetite, weight loss, and chronic intermittent vomiting and diarrhea. Vomiting is more common than diarrhea. Drinking and urinating more often than normal may be the first signs, and the principal reason for seeking medical attention.
In the early stages of liver disease the liver swells and enlarges. As the disease progresses, the liver cells die and are replaced by scar tissue. The liver then becomes rubbery and firm. This condition is called cirrhosis. It is not reversible. Before the liver reaches this terminal stage, it can recover from damage and heal itself to the point where your dog has normal liver function. This is possible if proper treatment is instituted early on; the extent of recovery depends on the exact cause of the liver damage. Eighty percent of liver cells must die before the liver begins to fail. The signs of liver failure are jaundice, hepatic encephalopathy, ascites, spontaneous bleeding, and dependent edema-swollen lower limbs. Treatment of liver failure is directed toward treating the liver disease that is causing it.
Jaundice
With impaired liver function, bile accumulates in the blood and tissues, staining the tissues yellow. This can be seen in the yellow appearance of the white of the eyes and in the mucous membranes of the gums and tongue. The inside of the ears is another area where yellow pigment can be detected. Bile excreted in the urine turns the urine dark brown (the color of tea).
Jaundice may also result from the breakdown of large numbers of red blood cells, such as in acute hemolytic anemia. Post hepatic bile duct obstruction can also cause jaundice.
Hepatic Encephalopathy
This is a type of brain dysfunction caused by high levels of ammonia and other toxins in the blood. Ammonia is a byproduct of protein metabolism, and is normally removed from the bloodstream by a healthy liver. When the liver is sick, ammonia accumulates to toxic levels and exerts a poisonous effect on the brain.
Dogs with hepatic encephalopathy develop incoordination, sporadic weakness, disorientation, head-pressing, behavioral changes, drooling, stupor, and mental dullness. Symptoms tend to wax and wane. They become more severe after a high-protein meal. Seizures and coma occur when hepatic encephalopathy is advanced.
Ascites
Ascites is the accumulation of fluid in the abdomen. In a dog with liver disease, it is caused by low serum proteins and increased pressure in the veins that supply the liver. A dog with ascites has a swollen or bloated look. Thumping on the abdomen produces a dull, flat sound.
Bleeding
Spontaneous bleeding occurs in dogs with advanced liver disease. Common sites of bleeding are the stomach, intestines, and urinary tract. Blood may be noted in the vomitus, stools, or urine. Punctate (pinhead-size) hemorrhages may be seen on the gums. Bruises can appear under the lips and skin. Major blood loss from spontaneous bleeding is relatively uncommon, but uncontrollable bleeding can be a serious problem if the dog is injured or requires surgery.
Causes of Liver Disease
A number of diseases, chemicals, drugs, and toxins can damage the liver. The liver is directly affected by infectious canine hepatitis and leptospirosis. It is frequently involved in heartworm infection, Cushing’s syndrome, and diabetes mellitus. Primary and metastatic tumors are a major cause of liver failure in dogs.
Chemicals known to produce liver toxicity include carbon tetrachloride, insecticides, and toxic amounts of lead, phosphorus, selenium, arsenic, and iron. Drugs capable of damaging the liver include anesthetic gases, antibiotics, antifungals, dewormers, diuretics, analgesics (including NSAIDs), anticonvulsants, testosterone preparations (Cheque drops), and corticosteroids. Most drug reactions are associated with excessive dosage and/or prolonged use.
Some plants and herbs can also cause liver failure; these include ragwort, certain mushrooms, and blue-green algae. Molds such as aflatoxin, which grows on corn and may contaminate foods, can cause severe liver damage.
A blockage of the bile duct by gallstones, liver flukes, tumors, or pancreatitis is uncommon, but becomes a consideration when a dog has unexplained jaundice.
Treatment: Blood tests, including bile acid assay, ultrasound, and CT scan, provide useful information, but the only definitive test is biopsy of the liver. The prognosis for recovery depends on how long the dog has been ill, the extent of liver damage, and whether the disease can be surgically cured or controlled with medications.
Infectious diseases respond to treatment of the underlying condition. Drugs and poisons frequently exert temporary effects that are reversed when the exposure is stopped. Bile duct obstructions and some primary tumors of the liver can be corrected by surgery.
In addition to treating the liver disease, it is important to control and prevent complications, particularly hepatic encephalopathy and bleeding. This may involve feeding a special diet that is low in protein, lowering blood ammonia levels, maintaining blood-clotting factors, preventing seizures, correcting electrolyte abnormalities, and administering antacids to prevent stomach and duodenal ulcers. Supplements such as SAM-e and milk thistle are useful in both restoring and maintaining normal liver function.
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