Your vet might tell you that the reason your dog isn’t feeling well is that he’s anemic. But this is only part of the story. Anemia has many causes, and because of this knowing how to successfully proceed depends on identifying that cause in your dog.
Read on to learn how we diagnose the cause of anemia in dogs, and what we do when we find it.
How would you know your dog is anemic?
Usually we find anemia by running blood tests. A complete blood count, or “CBC”, is a procedure in which all of the major blood cell lines – red blood cells, white blood cells, and platelets – are “counted” by a blood-analyzing machine. We know how many red blood cells a normal dog should have. Having less than this number is the definition of anemia.
From a strictly observational standpoint, anemia looks like a lot of other problems. Anemic dogs tend to be tired and lethargic, and sometimes their breathing is rapid and shallow. This is because red blood cells carry oxygen, and if there are fewer red blood cells it stands to reason that there will be less available oxygen in the body. They also typically have pale pink or even white gums.
Anemia isn’t a diagnosis
Like a lot of things we talk about in medicine, anemia isn’t really a diagnosis, it’s a symptom of an underlying disease. There’s always a cause of anemia, and successfully fixing the anemia means first identifying what’s causing it, and treating that.
When we talk about diagnosing anemia, we first try to put the problem into one of three categories, then go from there.
Hemorrhage
Hemorrhage, which is more succinctly described as “bleeding”, can occur on the outside of the body where we can see it, or on the inside, where we can’t. While deep cuts can cause what appears to us to be significant bleeding, they are almost never enough to cause anemia, unless they involve the severing of a very large vessel.
Most of the time bleeding that leads to anemia occurs into a body cavity, such as the thorax (chest) or abdomen. A dog that gets hit by a car can sustain a ruptured spleen, which will result in substantial blood loss into the abdomen. Dogs will also readily eat rat poison, which works by inhibiting clotting and causing spontaneous bleeding, often into the lungs and chest. And certain types of tumors can rupture and bleed into the inside of the body as well.
Slower blood loss within the body can lead to anemia as well. The classic example of this is ulcers in the stomach or intestines that bleed slowly into the gastrointestinal tract.
Decreased production of red blood cells
Quite a few diseases fall into this second category. Usually these are diseases of the bone marrow, which is the location in the body where red blood cells are produced. Cancer of the bone marrow can cause a decrease in the amount of red blood cells produced.
The hormone erythropoietin, which is produced by the kidneys, influences the production of red blood cells. When erythropoietin levels are low, fewer red blood cells are produced in the bone marrow. Dogs that have long-term kidney disease often suffer from anemia for this reason.
Drugs can also suppress red blood cell production. Estrogen is a great example, and used to be used commonly to treat urinary incontinence problems in spayed female dogs. However, because its use can cause mild anemia, we typically don’t use estrogen for this purpose anymore.
Destruction of red blood cells
Lots of diseases fall into this category. Infectious diseases, such as those transmitted by ticks and fleas, are probably the most common. Autoimmune diseases also cause destruction of red blood cells for reasons that we don’t really understand. And cancers of the blood vessels can destroy red blood cells as well.
Some drugs cause oxidative damage to red blood cells in dogs but not other species. Tylenol is a great example of this, and it’s one reason why we almost never use it in veterinary medicine. And ingestion of the mineral zinc in sufficient quantities can also lead to red blood cell destruction. This usually happens after a dog swallows pennies, which contain zinc, or ingests zinc-containing sunscreen or diaper rash cream.
Treating anemia
Sometimes treating anemia is relatively simple. This is usually the case when the anemia results from blood loss. If you can stop the loss of blood, either by closing the wound or treating the problem causing the bleeding, the bone marrow will eventually catch up, and the anemia will resolve. Sometimes the anemia is so severe that the patient needs a blood transfusion, but this is usually only the case with very sudden and large losses.
If the problem is infectious in origin, identifying the particular disease is critical to successful treatment. Most tick- and flea-borne diseases respond to the antibiotic doxycycline. Autoimmune causes of anemia usually must be treated over a long period of time with drugs that suppress the immune response and thus stop the red blood cell destruction. These dogs are always at risk for recurrence of the disease for the rest of their lives, and must be carefully monitored.
If cancer is causing the anemia, either bone marrow cancer or cancers of the blood vessels, treatment protocol differs, as does prognosis.