Polycythemia in dogs is a condition where there is an increase in the number or concentration of red blood cells in the circulatory system. It is the opposite of anemia, a condition where red blood cell count is too low. Polycythemia can be relative, transient, or absolute. Relative polycythemia happens when dogs’ plasma volume decreases, usually from dehydration, which means the relative number of red blood cells increases. Transient polycythemia happens when the spleen contracts in response to epinephrine, the stress, anger, or fear hormone, which results in an injection of red blood cells into the circulatory system. Absolute polycythemia happens when bone marrow increases production of red blood cells. All of these can result in similar symptoms, but it is important for a veterinarian to determine which type of polycythemia is affecting a dog before beginning treatment. Here is what you should know about the symptoms, causes, and treatments for polycythemia in dogs.
Symptoms Of Polycythemia In Dogs
The symptoms of polycythemia in dogs can worsen over time and result in further symptoms because high concentrations of oxygen in the blood can cause tissue damage if left untreated. That is why it is important to consult a veterinarian at the first sign of symptoms. If you see any of the following signs of polycythemia in your dog, get to the vet right away.
- Behavioral changes
- Changes in motor or sensory skills, especially vision
- Dark red, bluish, or pale gums
- Enlarged spleen or liver
- Increased thirst
- Increased urination
- Enlarged abdomen
- Difficulty walking
- Exercise intolerance
- Difficulty breathing
Causes Of Polycythemia In Dogs
The causes of polycythemia in dogs vary depending on the type. Absolute polycythemia can be further broken down into primary and secondary absolute polycythemia, which also have different causes. Here are several of the causes for each type of polycythemia in dogs.
Relative polycythemia – This is most often caused by dehydration, but it can also be caused by blood loss, shock, vomiting, diarrhea, kidney disease, hyperventilation, and any other condition that causes a decrease in the volume of plasma.
Transient polycythemia – This is caused by contractions of the spleen, which stores mature red blood cells. The contractions result from a rush of epinephrine, which is a response to anger, fear, excitement, surprise, or exercise. Usually it is beneficial, as red blood cells deliver oxygen to parts of the body and prepare dogs for physical activity, which is helpful in a flight or fight situation.
Primary absolute polycythemia – The cause of this condition is unknown. It happens when there is an increase in growth or formation of the bone marrow, which produces red blood cells.
Secondary absolute polycythemia – This happens when there is an increase in production of the hormone erythropoietin in the kidneys. Erythropoietin is the hormone responsible for stimulating red blood cell production in the marrow. The increase in erythropoietin can be caused by adapting to high altitudes, cancer, pancreatitis, kidney disease, hyperthyroidism, Cushing’s disease, heart disease, lung disease, or other problems with the circulatory system.
Treatments For Polycythemia In Dogs
Treatments for polycythemia in dogs also vary depending on the type and cause. Secondary absolute polycythemia tends to be the most difficult to treat. If your dog suffers from polycythemia, your veterinarian will determine the cause and prescribe treatment accordingly. Here are some treatments you might expect based on which type of polycythemia your dog is diagnosed with.
Relative polycythemia – Usually this is fixed by rehydrating the dog, sometimes with intravenous fluids.
Transient polycythemia – This is most often a temporary condition brought on by stress or excitement and resolves itself without treatment.
Primary absolute polycythemia – This is a chronic, rare disease that may be resolved by a phlebotomy, more commonly know as blood letting. A catheter is put in a central vein to remove blood that is too high in red blood cells, and fluids will be replaced intravenously to avoid a drop in blood pressure. The procedure may need to be repeated several times. Medications may also be prescribed to inhibit red blood cell production.
Secondary absolute polycythemia – The underlying cause must be diagnosed, and because there are so many potential causes of the condition, treatment can vary a great deal. Often treatment of the underlying cause resolves the polycythemia and no further treatment is required, though in some cases, phlebotomies may be needed to reduce the amount of red blood cells.