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My veterinarian ran some blood tests and said my dog's liver enzymes were elevated. What does that mean?

Your veterinarian may recommend doing blood tests for a variety of reasons, such as an annual wellness screening, prior to scheduling anesthesia or starting certain medications, or because your dog is acting sick. How the liver enzymes are interpreted depends upon the age and breed of your dog, history of certain medications, what (if any) clinical signs your dog has, as well as the specific lab results. A lot of times, the increase in liver enzymes is mild and self-limiting; rarely, it can indicate a serious underlying liver disease.

Which of the lab values are the liver enzymes?

The main liver enzymes that your veterinarian may look at include the ALT (alanine aminotransferase) and ALP (alkaline phosphatase).

Liver enzymes can be elevated from liver disease or can be secondarily affected by other diseases or processes outside the liver, e.g., pancreatitis (inflammation of the pancreas), intestinal disease, or certain hormonal diseases such as diabetes or Cushing's disease (overactive adrenal gland(s) producing too much cortisol). Certain medications, such as steroids (even in eye or ear medications) or phenobarbital (an antiseizure drug), can also cause elevations in liver enzymes.

Why are age and breed important?

Puppies will normally have an elevated ALP because ALP also comes from growing bones, not just liver cells. Some older dogs will have a benign accumulation of water, carbohydrates, or fat in the liver cells (so-called vacuolar hepatopathy). Others can develop nodules as an aging change. These diseases typically primarily cause an elevated ALP and do not really affect liver function or require treatment.

Elevations in ALT and ALP do not necessarily mean the liver is failing or not working properly. However, your veterinarian may recommend another blood test, called bile acids, to assess liver function. Another test that can be used to assess how the liver is working is bilirubin. This is the yellow pigment that builds up in the body when an animal is jaundiced. If the bilirubin is increased, this already indicates decreased liver function (unless the patient is also severely anemic), so bile acid testing in this situation is not indicated as it will not provide additional information.

Certain breeds are prone to particular diseases. For instance, an older Dachshund with elevated liver enzymes may have Cushing's syndrome. Labradors, Bedlington terriers, Westies, and Dobermans are predisposed to chronic hepatitis (inflammation of the liver). Shelties and Cocker Spaniels are prone to gallbladder problems. The fact that we see certain diseases in specific breeds suggests that there is a genetic/familial component to some of them, although other factors also play a role.

My dog isn't having any symptoms. Should I be worried about the elevated liver enzymes?

Dogs with severe liver disease can have a variety of clinical signs – decreased appetite, vomiting, diarrhea, neurologic signs, abdominal distention from fluid, and jaundice (yellow discoloration of gums, eyes, skin, etc). However, some dogs with significant liver disease may not show any clinical signs in the early stages. It is much better to diagnose and treat patients before they get sick. As a result, further workup may still be recommended, even if the dog is not having any clinical signs. An example of this is if your dog has a persistently increased ALT – this can be the first sign of chronic hepatitis, which can progress to liver failure. Some cases of chronic hepatitis are due to a toxic build up of copper in the liver that will continue unless you intervene medically.

If your dog isn't acting sick, your veterinarian may recommend a therapeutic trial of antibiotics (to rule out a possible infection), antioxidants (such as vitamin E,  Denamarin®, or ursodiol (a drug that increases bile flow and decreases inflammation). After a few weeks of therapy, the liver values would be rechecked. Further diagnostics would be warranted if the liver enzymes did not improve.

Besides blood tests, what else can be done to diagnose liver problems?

An abdominal ultrasound may be recommended by your veterinarian. Some diseases, such as a gallbladder obstruction or liver mass, can be readily identified on ultrasound. Ultrasound may also be useful to check for other diseases (besides a primary liver problem) in the abdomen that can affect the liver enzymes, such as pancreatitis.

Some, but not all, dogs with elevated liver enzymes need a liver biopsy to get a diagnosis. Liver biopsies can be obtained with a needle biopsy instrument using ultrasound guidance via a scope (laparoscope) or surgery. Oftentimes, the ultrasound is useful to determine if liver biopsies are needed and which biopsy method is most appropriate. Samples are taken for histopathology, culture (to rule out infections) and often for measuring copper levels. Your veterinarian may refer you to a specialist for further workup.

The treatment and prognosis depend on what is causing the elevated liver enzymes. An optimal treatment plan can be made with your veterinarian once the diagnosis is known.

Julie Allen, DVM, DACVP, DACVIM contributed to this article.