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.