The liver is a remarkable and complex organ that serves many essential functions:
- Metabolizing proteins, fats, and carbohydrates
- Storing essential vitamins, minerals, and nutrients
- Producing bile acids to support digestion
- Manufacturing proteins needed for various body functions
- Metabolizing medications, toxins, and waste for elimination from the body
Symptoms of Liver Disease
Some clinical signs indicating your pet may have liver disease are:
- Yellowing of the gums, skin, and eyes: known as jaundice
- Lethargy and severe depression
- Decreased appetite with vomiting and/or diarrhea
- Increased thirst and urination
- Neurologic change such as pacing, incoordination, confusion, and seizures
- Swollen and distended abdomen
Causes of Liver Disease
Infectious hepatitis – The most common bacterial infection that causes liver failure in dogs is Leptospirosis which is contacted through drinking water that is contaminated with wildlife urine. The most common viral disease is infectious canine hepatitis caused by adenovirus, which can cause liver inflammation and scarring. Both Leptospirosis and adenovirus are preventable by vaccination.
Hepatotoxicity – The liver is susceptible to adverse toxicity reactions due to its role in the metabolism. Common toxins that can cause acute liver failure include the artificial sweetener xylitol, wild mushrooms, Sago palm ornamental plants, and blue-green algae. Some drugs can also cause liver toxicity including acetaminophen, phenobarbital, and non-steroidal pain medications such as Carprofen.
Hepatic Vascular Disease – Hepatic vascular disorders are caused by abnormal blood vessel inside the liver that shunts or creates a bypass of the normal blood flow between the gastrointestinal tract, liver, and circulatory system. The decreased blood flow within the liver causes atrophy of the liver and a buildup of toxins. Hepatic vascular abnormalities are often inherited and occur most commonly in young small breed dogs.
Hepatic Cancers – Dogs afflicted with liver cancer are usually older than 10 years of age. Primary liver tumors include malignant hepatocellular carcinoma or hemangiosarcoma, and the benign hepatocellular adenoma. Cancers can originate in other parts of the body and metastasize to the liver, including lymphoma, pancreatic cancer.
Hepatic Storage Diseases – Disease can result when the liver accumulates excessive vitamins, minerals, or nutrients. Copper storage hepatopathy is a condition caused by an abnormal accumulation of copper in an animal’s liver. Some endocrine diseases including diabetes mellitus, thyroid conditions, and hyperadrenocorticism (Cushing’s Disease), can cause excessive storage of glycogen.
Immune Mediated Hepatitis – Canine Chronic Hepatitis is a long-term chronic inflammation of the liver that occurs due to the accumulation of inflammatory white blood cells in the liver. The chronic inflammatory process leads to progressive scarring. Excessive fibrous tissue replaces normal liver tissue and cirrhosis can result.
Biliary Disease – The liver can be severely impacted by diseases of the gall bladder and bile duct. Cholestasis and cholangitis are conditions in which obstruction or inflammation of the bile duct prevents the normal flow of bile from the liver to the small intestine. Biliary disease can occur due to gall stones, mucoceles, cancer, and infection.
Diagnosing Liver Disease
Diagnosis of liver disease may require a variety of tests including blood work, imaging, and pathology.
Liver enzymes – ALT, ALP, GGT, and AST are measured by a blood chemistry test. The hepatocellular enzymes ALT and AST are released from dying liver cells and are markers of hepatocellular damage. The biliary enzymes ALKP and GGT increase with any disease that impairs bile flow.
Total Bilirubin – Bilirubin is processed in the liver and subsequently released into the intestines as a component of bile. An increased concentration of bilirubin in blood, can occur if there is a problem with the uptake, processing, or release of bilirubin by the liver.Cholesterol – The liver manufactures cholesterol and excretes it via the gall bladder. If there is a severe decrease in liver function, this may be reflected by a decrease in cholesterol. Impaired bile flow or gallbladder function may result in an increase in cholesterol.
Albumin is a blood protein made by the liver. A severe decrease in liver function may be reflected by a decrease in albumin.
Bile Acids Test – This is a liver function test. The test is performed by taking a fasted blood sample, giving a meal, then taking another blood sample 2 hours later. A comparison made between the pre-meal and post-meal blood results gives us valuable information. The bile acids test is an accurate measure of liver function.
X-Rays – Radiographs are the best way of determining the size and shape of the liver. Liver enlargement, atrophy or shrinkage, and abnormal shapes or asymmetry may indicate disease. The presence of masses or tumors that change the shape of the liver can sometimes be visualized by the use of radiographs. Gallstones may also be identified on x-rays.
Ultrasound – Ultrasonography is the best diagnostic imaging modality to evaluate the internal structure of the liver. Ultrasound reveals any changes in the internal anatomy of the liver, including abnormal growths, nodules, or blood flow. This test also helps to reveal disease of the pancreas or gall bladder, which can be an underlying cause of liver disease or distress.
Cytology or Histopathology– Ultimately, the best way to reach a definitive diagnosis of disease is by microscopic examination of affected liver tissue. A large biopsy sample of the liver tissue can be obtained during an exploratory laparoscopic surgery. A smaller sample of tissue can be obtained by needle aspirate during an ultrasound procedure. Samples are sent to a pathologist for evaluation to determine what disease is present by microscopic examination of liver cells.
Treatment of Liver Disease
Treatment for liver disease is highly variable, individualized, and depends upon the underlying cause and severity of the liver disease in each dog.
Antioxidants – Supplementation with antioxidants help protect liver cells from damage, support liver function, and help promote regeneration. Supplements known to have the most benefit include vitamin E, zinc, silymarin, S-adenosylmethionine and silybin. The most commonly used supplement formulation used in pets is Denamarin.
Antibiotics – Patients with acute hepatitis of an infectious origin should be treated with broad-spectrum antibiotics. Ideally, the antibiotic choice should be based on test results including titer and bacterial culture. However, initiating treatment with an appropriate broad-spectrum antibiotic is indicated while awaiting culture results.
Bile Acids – Ursodiol is a naturally occurring bile acid used to treat biliary disease. Ursodiol decreases the amount of cholesterol produced by the liver and increase the bile flow through the liver and gall bladder. Ursodiol may also help break down gallstones.
Detox – With acute toxin exposures, a veterinarian can take steps to minimize absorption of toxins. Depending on the situation, the veterinarian may induce vomiting or pump a pet’s stomach, administer activated charcoal, and administer an appropriate antitoxin. For chronic storage diseases, medications such as D-penicillamine, a metal chelator, may be used to remove excessive copper from the body.
Inflammation control – Some dogs with chronic hepatitis respond to immunosuppressive treatment. Corticosteroid or cyclosporine therapy are the most commonly prescribed medications used in dogs with chronic hepatitis. Immunosuppression helps to slow the chronic inflammatory process that leads to scarring and cirrhosis in the liver.
Nutritional Therapy – Prescription therapeutic foods such as Science Diet LD or Royal Canin hepatic, are formulated with a low level of copper to help minimize its accumulation. These foods also have a precise blend of antioxidants to help minimize oxidative stress. The diets are highly palatable and calorie dense to support sick debilitated animals.
Surgery – Laparoscopic surgery may be warranted to visualize the liver and collect biopsy samples for diagnostic purposes. In the case of an obstructed gall bladder, surgery may be necessary and lifesaving to remove gall stones. Surgical removal of a liver lobe may be indicated to remove a liver tumor. Young patients with hepatic vascular abnormalities may need surgery to correct the vessel abnormalities and restore normal blood flow within the liver.
Prognosis of Liver Disease
The prognosis for dogs with hepatitis varies depending on the inciting cause, timeliness of diagnosis, and therapy provided. Early diagnosis and intervention are important for successful treatment of dogs with liver disease.
Dogs that have acute disease, including infectious hepatitis, hepatotoxicity, or gall bladder obstructions, that are promptly diagnosed and treated aggressively may make a full recovery and have good prognosis. Patients with chronic progressive liver disease, including hepatic vascular anomalies, storage diseases, and immune mediated hepatitis, can have a good prognosis. If these conditions are diagnosed and appropriate therapy is provided and maintained many pets can live up to 3 years with a good quality of life. Dogs with liver cancers have a varied prognosis. Patients with benign tumors may live a year or more and patients with malignant cancer may only live months.
If there is a delay in diagnosing a patient’s liver disease or failure to provide consistent appropriate therapy liver disease may progress into liver failure. If a patient reaches end stage liver disease they will have signs of organ failure including low blood proteins, low blood sugar, prolonged clotting times, fibrosis scaring, and ascites fluid accumulation. Once these signs develop, a pet has a poor prognosis and short survival time.