Causes of Liver Disease
There is no one cause of canine liver disease. It can be chronic or acute in onset and can be familial, hereditary/genetic, infectious, toxic, cancerous or of unknown origin, among others. Liver damage or disease can be caused by many things, including the following:
- Ingestion of or exposure to high levels of certain chemical toxins, such as insecticides, rodenticides, lead, selenium, arsenic, iron, phosphorus and carbon tetrachloride
- Ingestion of toxic levels of certain drugs, such as antifungals, analgesics (pain medications, including nonsteroidal anti-inflammatory drugs/NSAIDs), anticonvultants, antibiotics, anesthetic gases, dewormers, corticosteroids and diuretics. Most adverse drug reactions that lead to liver toxicity are associated with inappropriately high dosage and/or prolonged use
- Systemic infectious or other diseases, such as leptospirosis, heartworm infection, infectious canine hepatitis, canine adenovirus, diabetes mellitus, hyperadrenocorticism (Cushing’s disease) and hypothyroidism
- Cancer (neoplasia), which can be primary (starting in the liver) or metastatic (coming from elsewhere). May involve hepatocellular carcinoma (common), hepatocellular adenoma, biliary carcinoma or adenoma, hemangiosarcoma, leiomyosarcoma, lymphoma, islet cell carcinoma, adenocarcinoma, transitional cell carcinoma and many other forms or cancer
- Toxic plants, such as blue-green algae, mushrooms, lillies and ragwort, among many others
- Molds, such as aflatoxin
- Liver shunts (portosystemic shunts)
- Idiopathic chronic hepatitis (usually caused by an unknown autoimmune malfunction)
- Copper-associated hepatitis (often breed-related)
- Physical obstruction of the bile ducts caused by liver flukes, tumors, pancreatitis or gall bladder stones
- Fibrosis of liver tissue
- Vascular or circulatory disorders (congenital [present at birth] or developmental)
- Biliary tract disorders
- Infectious diseases (bacterial, fungal, viral)
- Liver abscesses
There are thousands of toxic substances that can damage the liver if ingested. Any heart or circulatory problem affecting blood flow to the liver can also cause liver disease.
Regardless of its cause, liver disease typically follows a predictable course, starting with liver swelling and enlargement, called hepatomegaly. As the disease progresses, liver cells begin to die (hepatic necrosis) and become replaced with scar tissue, known as granulation tissue. Over time, the liver becomes increasingly firm, with bands of fibrous connective tissue partitioning the liver into abnormal, irregular, rubbery nodules – a serious condition called cirrhosis. Unfortunately, once the liver becomes cirrhotic, the condition is irreversible. However, if liver disease is detected and treated before this terminal stage, the liver has the ability to regenerate enough tissue to function normally. The extent of functional recovery depends upon the extent of disease at the time of diagnosis. Authorities suggest that at least 70 or 80 percent of liver cells must be permanently damaged before irreversible damage sets in.
Preventing Liver Disease
Many causes of liver disease are not preventable. Of course, potentially toxic drugs, plants, chemicals and other substances should be kept well out of reach of companion animals, which will prevent exposure to them. Infectious diseases should be diagnosed and treated promptly to prevent liver damage, and routine vaccination protocols should be followed. All dogs should be provided with a high-quality diet, free access to fresh water, warm well-padded bedding and lots of play time to maintain overall health. Annual veterinary examinations, including routine blood tests, can identify elevated liver enzymes which may reflect early liver damage.
Certain infectious causes of liver disease are potentially contagious between dogs, including leptospirosis, infectious canine hepatitis and canine adenovirus. Leptospirosis may be zoonotic, meaning that it may be transmissible from dogs to people.
There are various treatment protocols for dogs with liver disease, depending upon the cause of the condition. The dog’s veterinarian is the best one to evaluate the extent of liver damage and recommend an appropriate treatment or management plan. The liver is a remarkably complex organ that can recover from damage or disease in multiple ways.