As a house call veterinarian, I treat a lot of senior pets, so therefore I run a lot of senior bloodwork. Every so often the blood results on a seemingly healthy older dog comes back with one abnormality – anemia. What is it, and how worried are we? Like everything else in medicine…it depends on severity and context. This article focuses on the mild anemia I see relatively often in older dogs that seem otherwise healthy. This does NOT discuss the big bad anemias like the auto-immune type.
Let’s go back to high school biology. Our bodies (people, dogs, cats, horses, you name it) need a certain number of red blood cells floating around in our blood. Red blood cells are what make our blood look, well, red. They are important for carrying oxygen and delivering it to every organ and tissue throughout the body. No red blood cells would mean no oxygen delivery, and important organs like brain, heart, kidney would shut down.
So what is anemia? That describes the condition of having fewer red blood cells than needed. There are a few ways to measure red blood cell count. The most common way is as a percentage of the total blood, called a hematocrit or Packed Cell Volume (PCV). For simplicity, I’ll generalize and say dogs typically have 40-50% of their blood as red blood cells (there is variation among breeds, so roll with me here). The rest is the fluid they float in, and some other types of cells. So we would call a dog anemic, or say it has anemia, if his red blood cell percentage was 33%. Or 10%.
Here’s where the difference becomes critical. Dogs who are a little anemic, with red blood cells at 33%, will feel good, act normal, and do OK. Dogs with only 10% red blood cells are dying and need immediate attention. So not all anemias are created equal!
When I do a senior blood test on a healthy older dog and discover a relative mild anemia of say, 33%, what next? This is the frustrating part. These mild anemias are like the “check engine” light on your car. It tells you something is wrong. It could be very minor and a non-issue, or it could be the beginning of a major problem. And we have no way of knowing which one just by the anemia.
Dogs (and cats) can develop a syndrome called “anemia of chronic disease.” That means one of many chronic diseases can cause a mild anemia. Not helpful when you’re trying to figure out what to do next. Cancer anywhere in the body may (or may not!) cause a mild anemia. Chronic liver disease, kidney disease, name-any-organ-disease can cause anemia. Diseases carried by ticks can as well. Severe dental disease can (like the dog needs every tooth extracted that hasn’t already fallen out). One chronic disease that does NOT cause anemia is arthritis. Go figure.
So we have this (apparently) healthy dog whose bloodwork is otherwise perfect and we have a little anemia. What now? If the dog is feeling and acting 100% normal and has not lost any weight, I remain calm and recheck the blood in a month. Sometimes it self resolves (no explanation but I’ll take it). Sometimes it gets worse and we know we’ve caught something early….just not sure what it is we caught. Or if it stays the same, very mild, we’re in this in-between “what next” stage.
Depending on how far you want to go, the next step is usually imaging. This can be x-rays of the chest and abdomen, and can be an ultrasound of the abdomen. We’re looking for cancer, I’ll just come out and say it. Sometimes instead of the imaging step, we’ll do blood tests for tick-borne diseases (like Lyme, ehrlichia, etc). We might check the poop for signs of a bleed in the intestines (called fecal occult blood). A lot depends on the breed and lifestyle of the dog.
If we do everything and it’s normal – yay! Many owners take the good news and run. However, just because we didn’t see something in the chest and abdomen doesn’t rule out anything in the skull or brain, so we keep that in mind. Still, if the dog is acting happy and healthy, blood panel stays perfect with the exception of the lack of some red blood cells, most owners are happy. I do recommend keeping tabs on it, just in case there’s a very subtle disease lurking we couldn’t find that is about to make its move. Usually I test every 3-6 months, depending on age and breed of dog, as well as severity of anemia.
In reality, I find something diagnosable (most often cancer) in a little under half the dogs I work up. So of the healthy older dogs with anemia, half of them both pursue diagnostics AND find something that usually is not good. The other group we either find nothing (yay?) on imaging, or we perform other tests, or we simple keep monitoring.
And, truth be told, you aren’t a bad person if you choose to not follow up with additional diagnostic tests. Again, this is a dog who is feeling great, acts like nothing is wrong, and without running that blood test, we would have never had any reason to suspect anything. I have many owners who elect to keep tabs on their weight, recheck the blood every so often to make sure disaster isn’t pending, and live a happy life with their dog.
So if your dog has a mild anemia, it’s particularly worth looking into if there is anything at all that has changed with your dog recently. If your dog is otherwise perfect, and you don’t want to put him through a lot, that’s totally fine as well.