Neutrophilia is an abnormal increase in the most common type of white blood cells in dogs, neutrophils. This is not a problem that develops on its own but is a symptom of a much larger issue. Neutrophilia may be the result of one of several causes. Once the underlying cause is treated, neutrophilia often ceases to be an issue. Laboratory tests are needed to diagnose neutrophilia and its underlying causes.
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Formation of Neutrophils
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Neutrophils are formed in the bone marrow of an animal and released into a dog's blood stream only for a short period of time. Once in the blood stream, they move into the body's tissues. Normally they circulate out and are destroyed in the liver or spleen or they return back to the bone marrow. When a part of the body becomes injured or infected, neutrophils begin to gather in that space and the body increases the output of neutrophils as well as other types of white blood cells, to fight off any effects of the injury.
Physiological Neutrophilia
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Physiological neutrophilia is the least worrisome type of neutrophilia. Physiological neutrophilia occurs most often in animals that are young and healthy. It can occur after a period of extreme fear, excitement, physical activity or during any time when an excess of the hormone epinephrine is released into the bloodstream. This is often a passing occurrence observed in a blood test. This type of neutrophilia may be the result of the stress incurred just from visiting the veterinarian. Often the body will correct itself within one to two hours after the event.
Stress Induced Neutrophilia
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Prolonged psychological and/or physical stress, such as transportation, traumatic injury, intense or prolonged pain, or even something as simple as boarding at a kennel, may cause a specific variety of neturophilia called "stress induced neturophilia". With stress induced neutrophilia, other factors will be present when a blood sample is taken. A decrease in several other types of white blood cells, including lymphocytes, which fight disease and eosinophils, which control allergic reactions. An increase in a white blood cell type called monocytes, which digest cellular waste, can also be observed in stress induced neutrophilia. Stress induced neutrophilia often resolves itself when the traumatic incident is over. This can take several days to several weeks.
Corticosteroids
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The use of corticosteroids, such as cortisone, can cause bone marrow to release an abnormal amount of neutrophils. The effects of corticosteroid induced neutrophilia occur from four to eight hours after the administration of the drug, and cease one to three days after treatment with the drugs has been stopped. Clinical observations similar to stress-induced neutrophilia may be present.
Inflammation and Infection
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Acute, or sudden, inflammation, infection or tissue death may result in neutrophilia. The drainage or removal of a septic, or infected, organ, tissue, or other area of focus may also increase neutrophils. The inflammation or infection causes the dog's body tissues to increase the demand for white blood cells, and also causes the bone marrow to release more neutrophils. Chronic infection or inflammation, such as pyometra, pyoderma or even leukemia, will often manifest as neutrophilia. Whether acute or chronic in onset, the underlying disease or issue must be resolved before the level of white blood cells will even out and neutrophilia will cease to be a problem.
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