By Mindy Cohan, VMD
The liver serves a role in many vitally important bodily functions. It is critical in the metabolism or breakdown of many drugs, enabling the body to use therapeutic medications. The liver detoxifies the blood, ridding the body of harmful chemicals and metabolites. In addition to its important filtration system, the liver is a very productive organ. By producing glucose from precursors other than carbohydrates, the liver serves to maintain adequate blood sugar levels. It is responsible for manufacturing cholesterol, a substance that is a precursor to bile and many important hormones. The liver is also responsible for producing vital proteins such as the blood’s clotting factors and albumin, which is necessary for maintaining fluid balance within the body’s circulatory system.
Here are five types of liver disease in dogs, as well as symptoms and treatment options.
Although the underlying cause of canine liver disease often remains a mystery, there are several agents known to cause destruction of hepatocytes, the cells that comprise the liver. Leptospirosis, a bacteria transmitted through contact with urine, poses a risk to both dogs and people. An adenovirus is responsible for canine infectious hepatitis. Fortunately, vaccines are available to prevent both. Systemic fungal infections such as Histoplasmosis can affect multiple organs, including the liver. Parasites such as flukes can have a primary effect on the liver or a secondary effect as is seen with heartworm infection.
Dog parents are often surprised to learn that many naturally occurring materials are dangerous to their pets. If ingested by dogs, plants such as sago palm, groundsel, and the bulbs of ornamental flowers such as tulips, daffodils, and amaryllis can cause multiorgan failure, which includes the liver. Severe liver damage can also occur following the ingestion of toxic mushrooms. One of the most common inciting agents of acute liver failure in dogs is xylitol, an artificial sweetener. With the increase in xylitol’s use in baked goods and peanut butter, dogs are at a greater risk for the sweetener’s life threatening side effects of liver cell death and low blood sugar. With an awareness of the potential danger posed by various toxins, pet parents can take measures to avoid their dog’s exposure.
In addition to taking precautions when it comes organic substances, dog parents also need to be mindful of various drugs that can induce liver damage. Some medications, although prescribed by a veterinarian, require periodic blood tests to monitor liver enzyme levels. Medications such as glucocorticoids (prednisone) and anticonvulsants (phenobarbital) can impact the liver, especially when given on a long-term basis. Certain antibiotics such as tetracycline can be harmful to the liver and need to be given with caution to dogs with any liver impairment. Although dogs are not as sensitive to acetaminophen (Tylenol) as cats, if an accidental overdose occurs, dogs can develop liver failure.
Several dog breeds have a genetic predisposition for developing liver disease. One such problem is known as a portal systemic shunt (PSS). The term refers to the abnormal blood vessels that carry blood from the intestines, stomach, and pancreas around instead of through the liver. Because the liver is bypassed, it is not able to detoxify the blood coming from other vital organs. Ammonia is a toxin that is normally broken down by the liver. Dogs with PSS develop abnormally elevated blood ammonia levels, which can result in neurologic symptoms such as head pressing, gait changes, behavior changes, and seizures. While the majority of liver shunts are congenital, some are acquired. Any breed can be affected, but some breeds such as Yorkshire Terriers, Maltese Terriers, Silky Terriers, Miniature Schnauzers, Old English Sheepdogs, Irish Wolfhounds, Cairn Terriers, and Miniature Poodles are predisposed. PSS can be managed both medically and surgically.
Copper storage disease is most commonly associated with Bedlington Terriers, but it is also recognized in West Highland White Terriers, Doberman Pinschers, and Labrador Retrievers. Copper is absorbed in the intestinal tract and is transported to the liver to be metabolized. Dogs who have an inherited inability to appropriately process copper will develop abnormally high concentrations of the element in liver tissue, which ultimately leads to liver cell damage. A liver biopsy is required to diagnose copper storage disease.
Metastatic disease (cancer that has spread from where it originated) is significantly more common than primary liver tumors. Primary liver tumors can originate in the liver itself or in the bile duct. Inciting causes of liver tumors include parasites and toxin exposure. Metastatic lesions can arise from tissues such as the lungs, pancreas, mammary glands, bone, and spleen. Whether your dog has been diagnosed with primary or metastatic liver tumors, an oncology consult is often recommended.
The symptoms associated with liver disease can be both specific and nonspecific. Manifestations such as jaundice and fluid accumulation in the abdomen and extremities can be seen with other diseases, but these abnormalities often prompt doctors to investigate a liver problem. Nonspecific symptoms include vomiting, increased thirst and urination, poor appetite, weight loss, personality and behavior changes, and seizures. Upon discovering clinical problems and abnormalities on routine blood tests, your dog’s veterinarian may recommend additional tests such as serum bile acids, blood clotting tests, an abdominal ultrasound, and liver biopsies.
The treatment recommendations for liver disease depend on the underlying cause of the problem. Chemical-driven liver damage intuitively requires stopping use of harmful drugs or toxic agents the dog has been exposed to. Infectious agents require treatment with antibiotics, antifungals, or antiparasitics. Certain conditions such as portal systemic shunts and gall bladder disease often require surgical and medical management. Dogs with copper storage disease require treatment with a medication that will remove heavy metal from the bloodstream, such as D-penicillamine. Liver tumors, depending on their size and location, are responsive to surgery and chemotherapeutic agents.
The prognosis for liver disease depends on the dog’s diagnosis, general health, and the stage in which the problem is discovered. Routine screening blood tests and awareness of the symptoms of liver disease are instrumental in early detection and an improved outcome.