High liver enzymes in dogs can have a multitude of causes, and the outlook may vary significantly. To help you sort through your dog’s liver enzyme elevations, integrative veterinarian Dr. Julie Buzby explains the four main liver enzymes (ALT, AST, ALP, and GGT) and discusses the causes, diagnosis, treatment, and prognosis for high liver enzymes in dogs.
I remember during my second year of veterinary school being a bit discombobulated by the alphabet soup that is the liver enzymes. ALP, ALT, AST, and GGT…Oh My!
Luckily, with 25+ years of experience under my stethoscope, I can now look at chemistry panel results and not bat an eye. It has become almost second nature to interpret high liver values and counsel my worried clients on what we should do next.
I know, though, that even most knowledgeable dog parents can feel overwhelmed if their veterinarian discovers their beloved canine companion’s liver enzymes are high. That’s why I wanted to share some of my expertise and insight with you.
Hopefully, this information will help you confidently advocate for your pup as you work closely with your family veterinarian to navigate the slightly murky waters of elevated liver enzymes in dogs.
- What are high liver enzymes in dogs?
- What does the liver do?
- What are the common liver enzymes in dogs?
- How do vets interpret high liver enzymes?
- What causes high liver enzymes in dogs?
- How worried should you be about high liver enzymes?
- What diagnostics will my vet use if my dog has elevated liver enzymes?
- How do you treat elevated liver enzymes in dogs?
- Will my dog need long term care or monitoring?
- What is the prognosis for elevated liver enzymes in dogs?
- Work with your veterinarian
- What was the cause of your dog's high liver enzymes?
What are high liver enzymes in dogs?
First, let’s get some terminology down. When your vet says that your dog has “high liver enzymes,” this isn’t a specific diagnosis. Instead, elevated liver enzymes (i.e. an increase in ALT, AST, ALP and/or GGT on bloodwork) are merely a symptom that can point to quite a long list of diseases or conditions.
These conditions can be things directly affecting the liver. But they are just as likely to be diseases in other parts of the body altogether. And to add to the confusion, there are many factors to consider when determining if elevated liver values are no big deal, or if they might indicate a serious problem.
Think of it this way. While high liver values are not inherently “bad,” they are still something you and your vet should take seriously. Elevations in liver enzymes can sometimes serve as an early warning sign of liver problems or other health issues. And as with other conditions, the sooner your vet finds and addresses the problem, the better the outcome usually is.
We’ll get to the nitty gritty of the liver enzymes and what they might mean for your dog in a bit. First, a primer on the liver will be helpful.
What does the liver do?
The liver is one of the larger organs in the body. And it sits tucked up in your dog’s abdomen under the ribs, snuggled between the diaphragm and the gastrointestinal (GI) tract. The liver is a powerhouse organ that performs literally hundreds of tasks. So it is no wonder it needs to take up a fair bit of space in the abdomen.
Among other things, the liver:
- Filters toxins from the blood
- Processes the nutrients from the food your dog eats
- Stores leftover energy from food for later use
- Makes proteins needed for vital processes like blood clotting
The liver also has a buddy—the gallbladder—which is a small, pear-shaped organ tucked into the liver. The gallbladder’s main job is to store bile, a fluid the liver produces to aid in digestion.
More specifically, bile is essential for digesting fats. When your pup eats a meal that contains fat, the gallbladder contracts. This squeezes a bit of bile through the common bile duct and into the small intestines. There, bile helps break the fat into smaller pieces that the GI tract can absorb. Then, as blood from the intestinal tract flows through the liver, the liver pulls out some of the bile components to reuse them again.
The gallbladder and all the bile ducts (i.e. pathways the bile follows through the liver tissue) make up the biliary system.
Additionally, the liver contains many enzymes. Enzymes are like tiny, special workers in your dog’s body. Imagine them as little helpers that do specific jobs to keep things running smoothly.
Since the liver has so many jobs to do, there are lots of different enzymes that work within the liver. These enzymes are typically detectable in the bloodstream at levels that fall into a “normal” range. But in some situations (e.g. liver injury or disease), liver enzymes leak out of the liver and into the bloodstream in higher amounts than normal.
A chemistry panel can pick up on these increased enzyme levels, alerting the vet to the fact that the dog has high liver enzymes.
What are the common liver enzymes in dogs?
Typically, when your vet says your dear dog has high liver enzymes, he or she is talking about alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT). These are the liver values that a common blood chemistry panel usually measures.
Sometimes a dog will just have an elevation in one liver enzyme. But in other cases, all the liver enzyme levels may be higher than they should be. Which liver values are elevated can give clues to the underlying cause, so it is worth understanding a bit about each enzyme.
Alanine aminotransferase (ALT)
ALT (alanine aminotransferase) is an enzyme that is found primarily inside liver cells (i.e. hepatocytes). However, muscles, the kidneys, and red blood cells also contain small amounts of ALT.
When the liver is healthy, ALT levels in your pup’s blood are low because most of the ALT stays inside the liver. However, if something is wrong with your dog’s liver, such as liver injury or inflammation, the liver cells can release ALT into the bloodstream. This makes ALT a sensitive marker of injury to liver cells, especially since, out of all the liver enzymes, it is the most specific indicator of a problem within the liver itself.
Since ALT is fairly liver-specific, there really aren’t many other issues besides liver damage that can cause elevations in ALT. Occasionally, severe muscle damage may cause ALT values to be high. But if this is the case, usually your veterinarian will see other obvious changes on the chemistry panel, such as a concurrent severe elevation in a muscle enzyme known as creatine kinase (CK).
Also, it’s worth knowing that the body clears ALT from the bloodstream quickly. This means if ALT is high, then the liver has suffered a recent injury or insult. This trait also makes ALT especially useful when monitoring a dog’s recovery after an acute liver injury because ALT levels decrease quickly once liver damage ceases.
Aspartate aminotransferase (AST)
AST (aspartate aminotransferase) is another enzyme that is found inside liver cells. It also occurs in moderate amounts in several other types of cells, like those within the heart and the muscles. AST generally increases in parallel with ALT. However, AST is less specific for liver injury than ALT because AST levels can also rise due to an insult to the heart, muscle, or from red blood cell destruction.
AST levels stay elevated in circulation for an even shorter time than ALT. This means AST levels will go down and (hopefully) normalize even faster than ALT levels in patients who have suffered a sudden and severe insult or injury to their liver that has now resolved.
Alkaline phosphatase (ALP)
ALP (alkaline phosphatase) is an enzyme found in liver cells too. But only certain liver cells—those that line the bile ducts within the liver—contain ALP.
While an elevated ALP in dogs often indicates a problem with the liver, gallbladder, or the flow of bile, it is not nearly as specific of an indicator of a problem in those organs as some of the other liver enzymes. Bone also produces ALP, so growing young dogs often have a mildly elevated ALP. Plus, ALP elevations also occur in patients with bone infections or bone cancer (i.e. osteosarcoma in dogs). And since high steroid levels can cause ALP levels to rise, dogs with Cushing’s disease in dogs and those receiving oral or topical steroids also commonly have increased ALP values.
This is just a snapshot. Many disease processes, both within the liver and in other parts of the body, can cause high ALP values. And mild to moderate ALP elevations can even be present with several age-related benign conditions.
So if your pup only has an elevated ALP, take a deep breath, check out my high ALP in dogs article, and know that the odds are in your favor that your furry family member will have a favorable prognosis.
GGT (gamma-glutamyltransferase) is also present in the liver cells lining the ducts where bile flows. It specifically works within the outer lining, or cell membrane, of those cells. Just like ALP, elevations in GGT are a marker of a problem with the flow of bile. The issue usually occurs either as the bile flows through the liver or as it exits the gallbladder.
In dogs, GGT is more specific for disease within the gallbladder or liver than ALP. And its levels are less likely to be high from other non-liver or non-gallbladder-related problems.
How do vets interpret high liver enzymes?
Often a chemistry panel will measure all four of these liver enzymes (plus many other values too). Being able to look at the ALT, AST, ALP and GGT at the same time is helpful for the vet because there are several patterns of enzyme elevations that can provide clues about the source of the issue.
1. Hepatocellular pattern
A hepatocellular pattern happens when the main elevations are in ALT and AST. Since both of these enzymes live inside liver cells, concurrent elevations in ALT and AST levels suggest that something has damaged the liver cells themselves.
2. Cholestatic pattern
In a cholestatic pattern, enzymes like ALP and GGT are higher than the ALT and AST levels. This pattern tends to indicate that there is a problem with the bile ducts or the flow of bile from the liver to the small intestine. This bile flow “traffic jam,” which can be caused by conditions like gallstones or a blockage in the bile ducts, is also called cholestasis.
3. Mixed pattern
However, sometimes things are not so cut and dry. Dogs may have a mix of liver enzyme elevations, including both hepatocellular (ALT and AST) and cholestatic (ALP and GGT) enzymes. This can suggest a combination of liver cell damage and issues with bile flow.
What causes high liver enzymes in dogs?
There are some specific diseases and conditions that tend to cause each pattern of elevated liver enzymes. This makes the pattern method useful when searching for the reason for the increased liver values.
However, there is also a second, equally useful approach to organizing the causes of increased liver values in dogs. It involves separating them into problems that are directly related to the liver and/or gallbladder (i.e. hepatobiliary) or that are not a primary liver or gallbladder problem (i.e. extra-hepatic). With the extra-hepatic causes, the liver enzyme elevations are due to the secondary effects of a disease or illness in another organ system.
Using a combination of both approaches, let’s take a look at the various causes of high liver enzymes in dogs.
Causes of a hepatocellular pattern
As a review, in a hepatocellular pattern, the ALT and AST are more elevated than the ALP and GGT.
Some common hepatobiliary causes (causes related to liver disease in dogs or gall bladder problems) of a hepatocellular pattern include:
- Chronic hepatitis
- Cholangiohepatitis (i.e. inflammation of the liver and biliary system)
- Copper hepatopathy
- Infectious causes
- Infectious canine hepatitis
- Hepatotoxic Medications
- Carprofen for dogs
- Certain chemotherapy medications
- Congenital portosystemic shunts (i.e. abnormal blood vessel that connects the liver and systemic circulation)
- Microvascular dysplasia (i.e. congenital abnormality of the microscopic blood vessels in the liver)
- Liver cancer in dogs
- Systemic cancer
Some common extra-hepatic causes of a hepatocellular pattern are:
- Pancreatitis in dogs
- Congestive heart failure
- Dental disease in dogs
- Inflammatory bowel disease (IBD in dogs)
- Seizures in dogs
Causes of a cholestatic pattern
In a cholestatic pattern, remember that the GGT and ALP are more elevated than the ALT and AST.
Some common hepatobiliary causes of cholestatic pattern include:
- Nodular hyperplasia (i.e. a benign condition that is common in older dogs)
- Vacuolar hepatopathy in dogs
- Cholangitis (i.e. inflammation of the bile ducts)
- Gallbladder mucocele in dogs
- Liver or gallbladder cancer
Common extra-hepatic causes of a cholestatic pattern are:
- Medications like steroids (i.e. prednisone for dogs) and certain anti-seizure drugs
- Inflammatory bowel disease
- Diabetes mellitus in dogs
- Hypothyroidism in dogs
- Cushing’s disease in dogs
However, real life is often messier, and not every dog reads the textbook. So it is important to remember that these categories are not hard and fast, and that many dogs will have a mixed pattern of enzyme elevation.
How worried should you be about high liver enzymes?
When looking at this huge list of causes, it can be easy to start to worry or feel overwhelmed. However, while high liver enzymes in dogs shouldn’t be ignored, it will hopefully ease your mind to know that there are some causes, like benign nodular hyperplasia, that really are no big deal. And there are even more conditions that affect liver values, but once identified, are easy to treat with no long-term negative consequences.
Here’s are some factors to consider when you and your veterinarian are deciding how concerned you should be about elevated liver enzymes:
The magnitude and persistence of the elevations
If your dog’s liver enzymes remain consistently elevated over multiple vet visits, this is a cause for concern. And so is a “significant elevation” in the liver values. Generally, the consensus is that if the value is more than three times the high end of the reference range, this counts as a “significant elevation.”
In short, a single mild elevation may not be alarming. But ongoing or significant increases in liver enzyme levels should prompt further investigation.
Your dog’s symptoms (if any)
Often, the vet may find high liver values on routine bloodwork in dogs who are otherwise feeling fine. This is typically less concerning than if the dog is showing signs of illness.
As a point of interest, high liver enzymes themselves don’t even cause symptoms that you can observe directly. Instead, the symptoms you might notice are usually related to the underlying cause of the elevated liver enzymes.
High liver enzymes that are accompanied by the following clinical signs are concerning. And they may indicate a more serious health issue.
- Jaundice (i.e. yellowing of the eyes, gums, or skin)
- Being a lethargic dog
- Loss of appetite
- Increased thirst in dogs
- Abdominal distention (i.e. a pot-bellied dog appearance)
It’s important to note that these symptoms are not specific to liver disease and can occur in various other health conditions. If you observe any of these symptoms in your dog, especially if they persist or worsen, it’s crucial to consult with a veterinarian.
Dogs with pre-existing health conditions like diabetes, Cushing’s disease, or inflammatory bowel disease may be at a higher risk of liver problems. Elevated liver enzymes in dogs with these or other underlying health conditions should be closely monitored and promptly addressed.
Changes in behavior
If liver disease progresses to liver failure, this can manifest as neurologic changes like confusion, disorientation, dull mentation, or even seizures. Therefore, you should always discuss any significant changes in your dog’s behavior with your veterinarian.
Age and breed
Your veterinarian will always consider the age and breed of your furry family member when deciding how concerned they are about elevated liver values. For example, puppies can have a mildly elevated ALP because they are growing. This isn’t a cause for concern.
Additionally, some dog breeds are more prone to certain liver conditions. For instance, Yorkies are the poster children for both portosystemic shunts and microvascular dysplasia. And Labradors are known to have both chronic hepatitis and copper hepatitis. Thus, if you have a breed with a known predisposition to liver issues, your veterinarian is likely to recommend being more proactive about working up any elevated liver values.
Follow your vet’s guidance
Your veterinarian will discuss these factors with you and make recommendations about how to proceed. Sometimes the answer might be to recheck the values in a few weeks or months. And in other situations, the vet may feel it is important to dig deeper to find the cause of the elevations right away.
What diagnostics will my vet use if my dog has elevated liver enzymes?
If your dog’s bloodwork shows high liver enzymes and the vet recommends investigating further, the good news is that despite the daunting list of different causes of liver enzyme elevation, the steps involved in the diagnostic work-up are relatively similar across the board.
If your vet has not already done so, he or she may recommend a chemistry panel, complete blood count (CBC), and urinalysis as the first step. The veterinarian will likely pay close attention to certain values on the chemistry panel, such as bilirubin levels, BUN, albumin, cholesterol, and glucose. All of these numbers can help assess liver function (which is not something the ALT, AST, ALP, and GGT levels can tell you about).
The vet may also recommend a bile acid test. This is another non-invasive laboratory test that checks for liver dysfunction. With this test, the vet draws a blood sample before and after the dog eats a small meal. The bile acid numbers before and after eating give the vet an idea of how well the liver is able to recycle and process bile. If the bile acids levels are high, this indicates the liver is not functioning optimally.
Additionally, if the vet suspects an infectious disease like leptospirosis, he or she may perform specific blood tests to check for antibodies or the presence of the infectious agent.
Finally, since liver disease can affect blood clotting, the vet may recommend performing a coagulation profile. This blood test can assess clotting times and ensure the liver is producing the necessary clotting factors. (However, a coagulation profile requires special tubes, handling, and a special machine, so it may only be available at certain veterinary hospitals.)
Imaging of the liver is almost always helpful in cases of elevated liver values. An abdominal ultrasound tends to provide more diagnostic information than abdominal X-rays. Ultrasound has the advantage of being able to evaluate the size and shape of the liver and check for abnormalities like tumors, gallstones, or blockages in the bile ducts. Plus, ultrasound can reveal subtle changes that might suggest that other underlying conditions, like pancreatitis or Cushing’s disease, are at play.
Additionally, in some complex cases, for instance if the vet suspects a liver shunt, he or she may recommend a CT scan. This can be a good way to provide more detailed images of the liver, blood vessels, and surrounding structures.
Sampling the liver
Obtaining a sample of tissue from the liver can help the vet look for cancer or inflammation, or for the build-up of copper seen in dogs with copper hepatopathy. There are two possible sampling methods.
One is a fine needle aspirate (FNA), which involves using a small needle to pull some cells out of the liver under ultrasound guidance. The other is a liver biopsy, a procedure in which the vet obtains a small piece of liver tissue for evaluation.
Many veterinarians start with liver aspirates before considering liver biopsies. This is the case because the vet can often perform the FNA with only mild sedation, and it is generally considered to be a low risk procedure. FNAs are good at checking for certain cancers and are non-invasive. But they don’t provide a large enough sample to assess for inflammation or to check copper levels.
On the other hand, liver biopsies provide a larger sample of tissue and are often the best way to determine exactly what is going on in the liver. However, they are a more intensive diagnostic. A liver biopsy comes at a higher cost and has an increased risk of bleeding, as well as the need for general anesthesia.
Work with your veterinarian (and possibly a specialist)
The specific tests that your veterinarian recommends will depend on your dog’s history, physical exam, and lab work. Often the veterinarian can perform some of the preliminary testing in-house. But there may be times when your vet may refer your beloved canine companion to a veterinary specialist near you for additional testing, procedures, or follow-up.
How do you treat elevated liver enzymes in dogs?
After reaching a diagnosis, your vet will work with you to formulate a plan.
Remember that high liver enzymes are a symptom of some other problem—either within the liver or in another organ system. Thus, the treatments can vary widely depending on the suspected cause of the elevations and your dog’s situation. As discussed above, your veterinarian will take into account which values are elevated, the magnitude of the elevation, and the dog’s symptoms, age, and breed, when creating the plan.
In some cases, benign neglect and monitoring are enough. But in other cases (for example, where values are consistently and significantly elevated), finding and addressing the root cause is essential.
When it comes to treatments, some of the options that might be on the table include:
In some cases, dietary changes can help support liver function. Your veterinarian may recommend a special prescription diet formulated to support liver health. These diets are designed to reduce the workload on the liver and provide necessary nutrients.
Medications for liver disease tend to fall into one of three categories—medications to treat the underlying cause of the disease, medications to support liver function, or medications targeted toward any unpleasant symptoms your dog is experiencing.
Some examples of the different medications in each category include:
Treating the underlying condition
- Antibiotics to treat bacterial infections
- Immunosuppressive medications to treat certain inflammatory or immune-mediated liver diseases
- Chemotherapy medications to treat cancers affecting the liver or gallbladder
Supporting the liver
- Antioxidant medications like Denamarin®, Milk Thistle, and SAM-E to help support liver function
- The medication ursodiol to improve the flow of bile
- Anti-nausea medications to treat nausea or vomiting
- Appetite stimulants for dogs to improve a poor appetite
- Pain medications for painful conditions like pancreatitis
- Fluids to improve hydration in dogs who are not eating and drinking or who are losing fluid from vomiting or having diarrhea
Management of the underlying condition
If the high liver enzymes are related to another health issue, such as diabetes, Cushing’s disease, or pancreatitis, treatments aimed at managing those underlying conditions are crucial.
In certain situations, surgery may be necessary to address issues like liver tumors, portosystemic shunts, gallbladder mucoceles, or bile duct obstructions.
Will my dog need long term care or monitoring?
During the treatment period (and beyond), working closely with your veterinarian and following his or her recommendations is so important. Depending on the situation, this may mean giving medications or a special diet, potentially long-term. And your vet will probably instruct you to monitor your dog carefully at home and report any changes or concerns promptly.
Additionally, chances are good that your vet will want to recheck your dog periodically. This is an important way for him or her to track your dog’s liver enzymes and make changes to the plan as needed.
What is the prognosis for elevated liver enzymes in dogs?
When your veterinarian tells you that your dog has any blood work abnormality, it is normal to feel concerned. Elevated liver values don’t have to be scary, though. There are many treatable causes. And to add to the good news, the liver has some regenerative capacity. This means that even if your dog’s liver is severely damaged, there is a chance that, with appropriate treatment and time, your precious pup can regain some of the liver function he or she lost.
However, occasionally, despite prompt diagnosis and aggressive treatment, the underlying cause of a dog’s liver disease is severe enough to carry a grave prognosis.
Some of the factors that can affect prognosis include:
The most crucial factor in determining the prognosis is the specific cause of the elevated liver enzymes. If the cause is something treatable, like a bacterial infection or a negative reaction to a medication, the prognosis may be very good with prompt treatment.
The degree of illness
If your dog has severe elevations in liver enzymes and is feeling extremely sick at the time of diagnosis, the prognosis may not be as favorable as in cases where the elevation is mild and caught when the dog is still asymptomatic. Plus, if there are other health issues or diseases present in addition to the high liver values, this can negatively impact the prognosis.
Work with your veterinarian
Now that you know the ABCs of high liver enzymes in dogs, you are equipped with the knowledge you need to advocate for your pup. Hopefully, you can breathe a little easier knowing that in many cases, with the right diagnosis and treatment, dogs with high liver enzymes can improve and lead long and healthy lives.
As discussed, your veterinarian will be your best source of information regarding your pup’s specific case and prognosis. He or she can work closely with you to develop a treatment plan and provide guidance on how you can best support your furry friend’s health. Together, you can help your dog keep living his or her best life, despite high liver enzymes.
What was the cause of your dog’s high liver enzymes?
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