Liver Disease in Dogs
by: Laura McLain Madsen DVM
What causes liver disease in dogs?
The term “liver disease” encompasses a range of different liver problems, including infections, congenital birth defects, inflammatory problems, and tumors. If your vet suspects a liver disorder, he will recommend additional testing to identify the exact problem. The treatment and prognosis will vary depending on the specific diagnosis. If the liver disease has advanced to the point that the liver is not able to perform its vital functions, the condition is termed “liver failure.”
What does the liver do?
The liver performs many life-supporting functions: detoxifying the blood, manufacturing proteins like coagulation factors (for normal blood clotting) and albumin, regulating sugar metabolism, metabolizing medications and chemicals, and producing bile to help digest food.
What are the symptoms of liver disease in dogs?
In many cases of early liver disease there may be no outward symptoms, or just mild complaints like occasional vomiting or decreased appetite. If liver disease progresses and becomes more severe or more long-term, many symptoms can be seen including decreased appetite, vomiting, diarrhea, weakness, increased thirst, increased urination, seizures (especially after meals), behavior changes, abnormal bleeding, abdominal distension, belly pain, and jaundice. Jaundice, also called icterus, is a yellow discoloration of the tissues. It is usually most obvious on the whites of the eyes, gums, and insides of the ear flaps. If the jaundice is severe, the skin all over the body will look yellow.
How is liver disease diagnosed?
The first step your veterinarian will recommend if she suspects liver disease is to run a lab panel, including a complete blood count (CBC), chemistry panel, electrolytes, and urine analysis. There are a number of values that vets look at on a blood panel that can be related to liver disorders, including liver enzymes, protein levels, blood sugar, and bilirubin. The liver enzymes are:
• AST (aspartate aminotransferase). This enzyme is normally contained within liver cells as well as muscle cells. Damage to liver cells allows AST to spill into the bloodstream. Because AST is also released from muscle cells, an elevated AST doesn’t necessarily indicate liver damage.
• ALT (alanine aminotransferase). Like AST, the ALT enzyme resides within the liver cells and is released into the blood with cell damage. Unlike AST, it is not produced by other organs in the body so is relatively specific for liver damage.
• ALKP (or ALP) (alkaline phosphatase). Whereas AST and ALT are elevated when there has been damage to liver cells, ALKP becomes elevated when the flow of bile from the liver to the gall bladder to the intestines is hindered. ALKP is also produced by intestines, bone, and kidney tissues and can be elevated by medications.
• GGT (gamma glutamyl transpeptidase). Like ALKP, the GGT enzyme is an indicator of an abnormality in the flow of bile.It is important to realize that if there is permanent destruction of liver tissue and scarring (cirrhosis), the liver enzymes may actually return to near-normal levels, because there are very few remaining liver cells healthy enough to manufacture the enzymes.
Other values on a routine blood panel that could indicate liver disease in dogs are:• Bilirubin.
Sometimes this is divided into “direct” and “indirect” bilirubin, but the distinction is not very important. Bilirubin is the yellow pigment responsible for jaundice. Bilirubin is formed from the destruction of hemoglobin (the oxygen-carrying red pigment in red blood cells) when old red blood cells are recycled by the body. Normally the liver excretes bilirubin into the intestines, but in liver disorders, particularly disorders which impede bile flow, bilirubin leaks into the bloodstream. Bilirubin can also accumulate in cases of excessive destruction of red blood cells (certain types of anemia) even with normal liver function.
• Glucose (blood sugar). Carbohydrates are metabolized by the liver to make glucose, so the blood glucose may be low in severe liver disease.
• Albumin. The liver manufactures this very important protein which circulates throughout the body. Albumin is responsible for the oncotic pressure of blood, which means the chemical attraction which keeps water in the bloodstream instead of allowing it to leak out. When albumin is low, as in liver failure, water leaks out of the vessels into the tissues (edema), chest cavity (pleural effusion) and/or abdominal cavity (ascites).
• BUN (blood urea nitrogen). BUN is generally thought of as a kidney indicator, and it is elevated in kidney disease. However, BUN is manufactured by the liver, so may be decreased in liver disease.
• Cholesterol. Like glucose, cholesterol may be low in liver disease due to a failure of the normal metabolic functions.
Other tests which may be recommended are:
• Bile acids. Bile acids are chemicals produced by the liver and excreted into the intestines to assist with digestion. In liver disease the bile acids accumulate into the bloodstream and will be elevated on a blood test. Typically your veterinarian will take two blood samples (before and after a meal) for this test.
• Coagulation panel. Normal blood clotting is the result of a cascade of interacting clotting factors. Most of these clotting factors are proteins manufactured by the liver. In liver disease, the circulating clotting factors are used up and spontaneous bleeding may result. Specific clotting tests which your veterinarian may recommend are the ACT (activated clotting time), PT (prothrombin time) and aPTT (activated partial thrombloplastin time).
• X-rays to look at the liver size and shape.
• Bacterial culture of bile or urine.
• Ultrasound to visualize the liver, as well as the gall bladder, blood vessels, pancreas, and other abdominal organs.
• Biopsy to get a small piece of the liver tissue to send to a pathologist for an exact diagnosis.
• Laparoscopy, which involves scoping the belly to look directly at the liver.
What are causes of liver disease in dogs?
Many disorders can cause liver disease in dogs. These include:
• Copper storage disease, in which the dogs have a genetic abnormality that allows copper to accumulate in the liver cells and damage them.
• Portosystemic shunt, a congenital birth defect. A shunt is an abnormal blood vessel that bypasses the liver, allowing blood to reach the brain without being detoxified.
• Endocrine problems: hyperadrenocorticism (Cushing’s disease, overactive adrenal gland), diabetes mellitus, and hypothyroidism (underactive thyroid gland).
• Disorders of the organs near the liver: pancreatitis (inflammation of the pancreas), cholecystitis (inflammation of the gall bladder), gall stones, and intestinal disease.
• Problems that cause decreased blood flow to the liver: anemia, congestive heart failure, and shock.
• Trauma: being hit by a car or kicked.
• Infections: viruses (canine infectious hepatitis), bacteria (leptospirosis, abscesses, bacterial spread from periodontal disease), parasites (heartworm; in severe cases the worms move “upstream” through the blood vessels from the heart to the liver).
• Cancer: hepatic carcinoma, lymphoma, hemangiosarcoma, and metastatic cancer.
• Drugs or medications: phenobarbital, non-steroidal anti-inflammatory drugs (carprofen [Rimadyl®]), sulfa antibiotics, antifungals, and cyclosporine.
• Toxins: xylitol (a sugar substitute), cycad (Sago) palm, Amanita “Death Cap” mushrooms, acetaminophen (Tylenol®), and blue-green algae.
• Chronic active hepatitis, an autoimmune condition in which the immune system targets liver cells in error.
Are certain breeds at risk?
Congenital shunts are more common in small breed dogs, especially Yorkies and Maltese. Labradors and Dobermans are prone to chronic active hepatitis, and Goldens and German shepherds are prone to hemangiosarcoma. Copper storage disease is seen in Bedlington terriers.
How is liver disease in dogs treated?
Treatment will depend on the exact nature of the liver disease, such as antibiotics for infection or immunosuppressants for autoimmune disorders. In general, sudden-onset liver problems are treated with intravenous fluids, anti-nausea medications, antibiotics, and pain medications. Surgery may be necessary to repair shunts or remove tumors. Long-term management may include a prescription diet, supplements, and medications to prevent inflammation and scarring.
Return from Liver Disease in Dogs to Dog Health