So, your vet has told you that your dog has raised liver enzymes. Understandably, you’ll probably have a few questions.; is it serious? What might have caused it? And, what exactly does it mean? As is often the case, there isn’t a single answer to any of these questions. So in this article, we look at some of the most common causes, the underlying conditions and the role of the liver in your dog.
What does a dog’s liver actually do?
First of all, let’s talk about what livers do. A lot of confusion surrounds this: we all know that livers are important, but many people find it hard to explain why. This is probably because they have a variety of different complicated jobs, mostly connected to metabolising food.
I like to think of them as the body’s boiler. Not because they literally generate heat, although they certainly do. But they are also a hotbed of metabolic reactions, releasing energy and other products from food, so that the body can use them. They also clear dead blood cells, toxins, poisons and waste products from the blood and make bile and some essential vitamins and minerals.
In short, our livers are vitally important and luckily, they are regenerative. That is, animals can grow new liver tissue when their livers are damaged. As the liver starts to struggle, lumps of extra tissue grow on the side. Sadly, the capacity of the new liver tissue is often limited. In severe, ongoing cases, the liver can become large with increasingly few useful cells and additional lumps on the side.
As an aside, this explains why it can be difficult to tell the difference between a cancerous liver and one that isn’t working but has tried to regenerate. A vet might tell you that a liver looks irregular or lumpy, but it may be regeneration or may be cancer, so biopsies are often needed.
Anyway, back to liver enzymes, which are made by the liver and found in the blood. They have slightly confusing names which are usually shorted to initials. The concentration (amount per ml) of these chemicals reflects what’s going on in the liver. I’ll focus on two basic ones:
ALT (alanine aminotransferase)
This is found in liver cells. If liver cells break down for any reason, it is released into the blood. When ALT levels in the blood are high, it tells us that liver cells are breaking down more quickly than usual. What it doesn’t tell us, is why. The liver might be perfectly healthy, but the metabolism too fast: this is common in Hyperthyroid cats. The animal may have recently had a dose of a drug that the liver finds difficult to cope with, such as a steroid. But it may also be a sign of a serious breakdown of liver cells.
ALKP (Alkaline Phosphatase)
Is found on the cell membranes (the outer borders) of liver cells and the bile duct. The ALKP in the blood will increase when bile is not flowing properly out of the liver. This may be because the liver is inflamed and thus preventing it. It will also increase with certain drugs, hormonal diseases and bone growth in young dogs.
Liver enzymes are a piece of the puzzle
The problem with liver enzymes is that they don’t tell us which of these things are causing the elevation. They are useful for ‘screening,’ i.e. for looking out for pets that might have a problem with the liver. If the vet knows of a possible reason for the increase in liver enzymes e.g. hyperthyroidism or poisoning, they may treat the underlying cause rather than investigating further and run the liver test again later on. Very often, however, further tests are needed in order to work out more.
These tests may include an ultrasound to look directly at the liver tissue, or a bile acid stimulation test (BAST). This evaluates how well the liver is working and whether it needs extra support. Another way to get a better idea of what’s going on in the liver is a biopsy; in which a small amount of liver is removed and examined under a microscope.
So in short, having raised liver enzymes isn’t a diagnosis, but a small piece of the jigsaw to find out what is going on with your pet.
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