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My Dog Has a High Red Blood Cell Count

High Red Blood Cell Count in Dogs

If your dog has a high red blood cell count, the medical term for this clinical presentation is polycythemia. While anemia is the decreased circulation of red blood cells, polycythemia in dogs consists of the increased concentration of red blood cells circulating within the dog's body. While the number of red blood cells circulating in the body are important as red blood cells carry oxygen, as with many things in life, too much of a good thing can be harmful. If your dog has a high red blood cell count, you may want to learn more about what causes this condition and what can be done about it.

dog blood test

My Dog Has a High Red Blood Cell Count 

If your dog has a high red blood cell count, it helps to better understand what is normal and abnormal when it comes to red blood cell counts in dogs.

When it comes to high red blood cell count in dogs (polycythemia), what is generally being calculated is a dog's hematocrit which isthe volume percentage of red blood cells in the blood.

Normal hemotocrit values in dogs range between 36 and 55 percent. Usually, clinical signs in dogs are seen when the hematocrit rises above 65 percent, explains veterinarian Dr. Joey.

Polycythemia in dogs can be divided into primary and secondary. When it is primary (polycythemia vera), the issue stems from the bone marrow which is where red blood cells are produced. In this case, the bone marrow is responsible for producing too many red blood cells.

In secondary polycythemia, the condition occurs secondary to chronically low oxygen levels (hypoxia) or as a response from the kidneys producing abnormal levels of erythropoietin, a hormone that tells the body to make more red blood cells.

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Causes of Increased Red Blood Count in Dogs 

dog trick

Dogs with high red blood counts often may feel poorly.

Secondary polycythemia is far more common than primary in dogs, and as mentioned, is associated with abnormal levels of erythropoietin. Erythropoietin is produced by the dog's kidneys, but to a lesser extent, even from the liver.

The production of erythropoietin, as already stated, takes place when there are lower than normal oxygen levels. It is therefore important investigating why there are lower than normal oxygen levels.

Increased Altitude

Polycythemia can take place as a result of high altitude. This physiological response is a form of adaptation to fast exposure to high altitudes and is often called altitude sickness. In this case, the body is responding to the lower oxygen levels found at higher altitudes by increasing hematocrit and hemoglobin levels. This helps increase the amount of oxygenated blood to the body.

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A Matter of Dehydration

If your dog has a high red blood cell count, dehydration can be a cause. Dehydration takes place when your dog's water loss exceeds his water intake. Often, dehydration in dogs can take place when affected dogs are suffering from fluid loss from repeated or prolonged vomiting and diarrhea. This form of polycythemia can be resolved with fluid replacement therapy and tackling the underlying cause for the vomiting and diarrhea if found.

Heart Disease

In a young dog, it is possible that some type of congenital heart disease may be to blame for the higher red blood cell count. Chronic heart disease such as congestive heart failure, or abnormal flow of blood from the right side to the left side of the heart (cardiac right-to-left shunts) can also be potential culprits. If the vet suspects a heart problem, echocardiography (heart ultrasound) is a good diagnostic test to consider.

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Lung Disease

When the lungs are affected this can lead to reduced oxygen levels, triggering an increased production of red blood cells. Lung disease may include pulmonary fibrosis, emphysema, lung parenchymal disease and chronic obstructive pulmonary disease. As the blood becomes more viscous due to its concentration, it can also lead to pulmonary arterial hypertension as a secondary complication.

Kidney Disease

A dog's kidneys may be affected by a variety of types of cancer and these may cause disruption in the kidney's production of erythropoietin, a hormone that triggers the spleen to produce red blood cells, a process known as erythropoiesis. Types of kidney cancer include renal carcinoma, renal lymphosarcoma, renal fibrosarcoma and other types of tumors. Non-cancerous causes include pyelonephritis (kidney infection). Important tests include an ultrasound of the dog's kidneys along with oxygen saturation or blood gas measurements.

Hormonal Issues 

Over active adrenal glands can be a cause in the case a dog has a high red blood cell count. In this case, the increased red blood cells in affected dogs is usually mild. In dogs suffering from Cushing's disease (hyperadrenocorticism) the high numbers occur because cortisol has an erythropoietic effect on the bone marrow (capacity to stimulate the bone marrow to produce more red blood cells. A similar effect can be found in dogs being administered corticosteroid drugs (steroids) or androgen drugs.

Did you know? In some cases, slight elevations in red blood cell count can be caused by excessive stress or excitement when the blood is drawn. What happens in this case is that the dog's spleen contracts and the adrenaline released causes the erythrocytes to raise a little higher (stress-polycythemia).

The tissue sample taken from the liver is checked under a microscope.

The tissue sample taken from the liver is checked under a microscope.

At the Vet's Office 

Diagnosis of polycythemia in dogs derives from blood tests checking for increased numbers of red blood cells. It is not unusual for dogs to also show increases in hemoglobin concentration and leukocytes (white blood cells).

The vet will have to investigate as to why a dog has a high red blood cell count. The underlying cause will need to be found so to initiate appropriate treatment. The vet may ask questions about the dog's symptoms, if the dog is on any medication and other reports that may help in diagnosis.

Further tests may include urinalysis, an electrolyte panel, hormone assays, x-rays and ultrasound images.

If several tests are run with no hints as to what may be wrong, it may help to check for bone marrow issues. A bone marrow biopsy may be needed and sedation or anesthesia is usually required for this test. The sample will then need to be sent to a pathologist so to look at the sample. This can help a bone marrow disorder (polycythemia vera). Treatment for this disorder requires phlebotomy, fluid replacement and administration of hydroxyurea. 

Treatment varies based on underlying causes and may include administration of fluids, electrolyte supplementation, correcting or ameliorating hormonal issues, cardiac issues, pulmonary issues and kidney issues, etc.

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