David Twedt, DVM, DACVIM
Whether a veterinary patient is symptomatic or asymptomatic, use this guide to help you get to a diagnosis.
You just got your laboratory report, which shows abnormal liver enzyme (e.g. alanine transaminase [ALT], aspartate aminotransferase [AST], gamma-glutamyltransferase [GGT] and alkaline phosphatase [ALP]) activity. The frustration begins. How much do you need to worry about it? The patient may have primary liver disease, but a nonhepatic condition resulting in secondary liver problems is more likely. It's important to find the exact cause, but the path to a diagnosis can be tricky to navigate-especially if the dog is asymptomatic.
Use the algorithm below as a guide for working up dogs with abnormal liver enzyme activities:
Click on the image to access a printable PDF.
If the patient is symptomatic:
When I have a sick dog with abnormal liver enzyme activities, the first thing I do is look for a primary, nonhepatic cause. Could it have gastrointestinal (GI) disease, pancreatitis, heart failure, septicemia or some other underlying disease?
If I identify a nonhepatic disease that could be the cause, I treat that first. If, on the other hand, I can't find anything, I work up the patient's liver.
Here's my list of liver workup considerations:
If the patient is asymptomatic:
Determining what to do with an asymptomatic dog is more complex. First, I perform a full physical exam to make sure I'm not missing some occult disease, such as an endocrine or metabolic disease. I then check the patient's drug history, as certain drugs (such as corticosteroids) can cause liver changes. I also check to see whether the patient is being given alternative medications because some herbals can cause liver disease as well.
If I don't find anything and the animal's completely healthy, I repeat the liver enzyme profile in six to eight weeks. During this interim period, I may consider giving the patient liver support medications (like S-adenosylmethionine, milk thistle, vitamin E or other antioxidants) or a course of antibiotic therapy if I suspect a bacterial infection (such as leptospirosis or bacterial cholangitis).
If the liver enzyme activities are still abnormal and the patient is still asymptomatic at the end of this six- to eight-week waiting period, I recommend to the client that we need to further investigate the patient's liver.
One of the things I often do at this point is check the patient's bile acid concentration. If the patient has an abnormal bile concentration and abnormal liver enzyme activities, I have strong evidence for recommending a liver workup because it suggests there is altered liver function of portal vascular shunting.
Dr. David Twedt is a professor in the Department of Clinical Sciences at Colorado State University.