by Jessica Vogelsang, DVM
Ask anyone to name the vital organs of the dog and you’ll get the usual: kidney, heart, lungs, brain, but for some reason people keep forgetting the liver. It may not look like much—a large, muddy brown-colored wedge of tissue sitting motionless in the abdomen—but don’t be fooled; the liver is as vital to life as an organ can be.
Due to its central role in the body, the liver is susceptible to a wide variety of problems that can threaten the health of dogs, so it’s important for owners to be aware of the signs and causes of liver disease in order to keep your pet in optimum health!
Signs of Liver Disease
The liver is a multi-purpose organ: it detoxifies the blood, helps break down drugs, metabolizes sources of energy, stores vitamins and glycogen, produces bile acids necessary for digestion, and manufactures important proteins necessary for blood clotting. Because of its behind-the-scenes role in so many important bodily functions, liver disease can manifest as a wide variety of symptoms depending on the vital function affected. Liver disease often has a cascade effect on other body systems.
One of the most common symptoms of liver disease is jaundice, a yellowish tinge to the skin most often noticed in the eyes, gums, and ears. The liver is responsible for excreting bilirubin, a by-product of red blood cell breakdown. When the liver isn’t functioning as it should be, this bilirubin builds up in the blood and leads to the yellowish appearance of the patient.
Hepatic encephalopathy is another common sequelae to liver disease. Hepatic encephalopathy refers to a collection of neurologic signs that occur in pets with liver disease and includes seizures, disorientation, depression, head pressing, blindness, or personality changes.
Other common symptoms of liver disease are gastrointestinal signs, such as decreased appetite, vomiting and diarrhea, weight loss, increased drinking and urination, and changes in stool color. Dogs may develop fluid retention in the abdomen, commonly referred to as ascites.
Your veterinarian can recommend diagnostic tests to evaluate your pet’s liver function and determine the cause of the liver disease. Commonly recommended tests are blood tests, abdominal ultrasounds, x-rays, and urinalysis.
Common Disorders of the Canine Liver
Vessel Abnormalities: In young dogs, one of the most common liver disorders is a birth defect called congenital portosystemic shunt. In these cases, a blood vessel is present that bypasses the liver, causing a buildup of toxins that the liver would normally take care of. Congenital portosystemic shunts are suspected in young dogs who have stunted growth, develop seizures, or seem disoriented.
In older dogs, we more commonly see acquired shunts, which develop when there is a blood pressure backup in the liver due to hypertension or cirrhosis. In an effort to get around the “jammed” region, new vessels grow to bypass the blocked area, but they also bypass the liver cells themselves.
Treatment depends on the anatomy of the shunt. If it consists of one large vessel outside of the liver, as is more common with congenital shunts in small breed dogs, surgery can be very successful. Shunts inside the liver or those consisting of multiple vessels may not be surgically repairable, and in those cases the patient has to be managed with a low protein diet and medications to help reduce the amount of toxins in the blood. In these cases, the liver problem isn’t cured, but instead the emphasis is placed on controlling the symptoms.
Endocrine Diseases: Certain diseases that affect the endocrine glands can lead to liver problems. Diabetes mellitus, hyperadrenocorticism (Cushing’s disease), and hyperthyroidism can all cause impaired liver function because of their effects on the organ. In these cases, treating the underlying endocrine disease is the most important component of improving liver function.
Infectious diseases: Because the entire blood volume passes through the liver, it is especially susceptible to a variety of infectious diseases. The liver can be infected by bacteria, viruses, parasites, or fungi.
The most common viral disease associated with the canine liver is infectious canine hepatitis, which can cause inflammation and scarring. This is a vaccine-preventable disease.
Leptospirosis is a bacterial infection that can lead to liver disease, though many people associate it more with kidney disease. Dogs are infected with leptospirosis through contaminated water sources, and the disease can be spread to humans.
Leptospirosis is diagnosed by blood test or tissue biopsy. While it can be challenging to diagnose due to the wide variety of nonspecific clinical signs, the bacterial infection can be cleared with early treatment. Secondary liver and kidney damage may be permanent. Commercial vaccines for leptospirosis are available for at-risk dogs.
Coccidioidomycosis and histoplasmosis are the most common fungal causes of liver disease. Dogs are exposed through spores in the environment. These fungal infections can be difficult to clear and often require months of treatment with anti-fungal medications. Because of the difficulty in treating fungal disease of the liver, the long-term prognosis is guarded.
Liver masses: Dogs are susceptible to several types of liver masses. Liver cysts can be present from birth or acquired with age. Though often benign, large or growing cysts can cause symptoms of liver disease. Surgical excision is usually curative.
Liver cancer: Cancer of the liver comes in two main forms—primary tumors, which originate in the liver, and secondary or metastatic tumors, which means they spread from another area in the body. Primary tumors are less common than metastatic ones. Depending on the type of cancer, location, and number of masses, treatments may include surgery, chemotherapy, radiation, or a combination.
Breed Specific Liver Diseases
Certain breeds of dogs are predisposed to specific liver conditions. Copper storage disease is a known problem in Bedlington terriers, Doberman pinschers, Skye terriers, and West Highland white terriers. In these dogs a metabolic defect causes copper to remain in the liver, leading to chronic hepatitis. Amyloidosis, caused by a malformed protein that accumulates in the cells, is a disease of Chinese Shar-peis.
Is Liver Disease Fatal for Dogs?
Depending on the severity of the disease and whether or not the underlying cause can be treated or eliminated, the prognosis for canine liver disease varies. If the cause is addressed before long-term damage occurs, the prognosis can be excellent. The liver is the only visceral organ known to regenerate, so in that respect it is truly remarkable.
Chronic or severe liver disease, however, has a poorer prognosis. In those cases, treatment is limited to managing the progression of disease and minimizing symptoms.
The most common medical management involves a higher carbohydrate/low protein diet to reduce the amount of circulating ammonia in the bloodstream, vitamin supplements, lactulose to bind toxins in the gut, antibiotics, and vitamin K if the patient has bleeding problems. It is essential that your veterinarian monitor your pet regularly if he or she has liver disease in order to control the symptoms.
Even with intensive management, many patients die of their disease, though good control extends the length and quality of their lives.
How Can Liver Disease be Prevented?
Not all cases of liver disease can be prevented, but certain precautions can reduce the risk of specific diseases. Dogs should be vaccinated for infectious canine hepatitis and, for some dogs, leptospirosis. Keep your pet away from known toxins. And most importantly, know the signs of liver disease and see the vet sooner rather than later if you are concerned! Early intervention and treatment is one of the key factors in treating liver disease and preventing serious signs.