|Purred: Mon Jun 25, '07 8:33pm PST |
|The many possible causes of anemia can be divided into three categories. Blood loss anemia is caused by the leaking of blood out of the vascular system. Hemolytic anemia is the result of the destruction of red blood cells circulating within the blood stream. Nonregenerative anemia refers to a decrease in erythrocyte production.
An in-hospital test called a "packed cell volume," or PCV, will approximate closely the percentage of red blood cells present. However, the veterinarian will typically opt to perform a complete blood count or CBC, which not only provides a more exact count of the red blood cells, but also measures the white blood cells and the platelets.
A CBC will tell the veterinarian whether the anemia is regenerative or nonregenerative. A regenerative anemia is one in which the bone marrow has released new red blood cells into the circulation in an attempt to replace the ones that were missing. If the initial CBC results suggest a nonregenerative anemia, it is possible either that the bone marrow has not had adequate time to react to the anemia or that the bone marrow is not able to produce the new red blood cells for some other reason. CBCs are usually run periodically until the patient's red blood count is stable and has returned to normal. If an animal has a true nonregenerative anemia, it will be necessary to determine the cause by means of further diagnostics. These may include fecal examination for blood parasites, urinalysis, serum chemistry, or bone marrow aspiration.
Animals get anemia for many different reasons. The most common ones are drug or toxin reaction, disease, and blood loss. Many common household products pose a serious toxic threat; acetaminophen, the active ingredient in Tylenol, is among the deadliest. Onions, whether cooked, raw, or dehydrated, are also especially dangerous. Other anemia-inducing substances include anti-inflammatory medications like aspirin, zinc, and propylene glycol, which is sometimes found in canned food.
Certain infectious diseases that animals contract are immune-mediated -- that is, the body begins killing its own red blood cells, resulting in hemolytic anemia. These diseases are more common among dogs. Other infectious diseases that can lead to anemia include the feline leukemia virus, feline immunodeficiency virus and blood parasites such as Haemobartonella and Babesia. Cancer and kidney failure, as well, can make a cat or dog anemic.
Blood loss, of course, means fewer red blood cells, so animals that have lost blood through trauma often become anemic. Fleas are literally bloodsuckers and are especially threatening to kittens and puppies, which are smaller and have less blood than adult animals.
Treatment varies according to the underlying cause of the anemia. With severe anemia, a blood transfusion is needed to replace the lost blood. In order to treat the underlying disease that is causing the anemia, intravenous fluids and certain medications may also be necessary.
Some specific anemia conditions include:
* Kidney failure. Anemia of chronic failure is primarily associated with reduced stimulation of bone marrow to produce red cells due to low production of the hormone erythropoietin
* Hemoglobin oxidation. Hemoglobin carries the oxygen inside the cell so reduced function of the hemoglobin leads to Heinz body anemia or methemoglobinemia. Oxidation interferes with red cell function.
* Blood parasites (such as Mycoplasma haemofelis and Mycoplasma haemominutum, formerly called Haemobartonella felis)
* Blood type incompatibility hemolytic anemia; where red cells burst (neonatal isoerythrolysis, transfusion reactions)
* Virus-associated or drug-related bone marrow disorders (aplastic anemia, or larger than normal red blood cells produced in FeLV-infected cats)
* Parasites. Hookworms or fleas (heavy infestations, especially in kittens)
* Trauma blood loss (hit-by-car, deep penetrating wounds)
* Abnormal red cell production due to inherited conditions (osmotic fragility syndrome, Pyruvate Kinase deficiency, congenital porphyria)
* Uncommonly, see iron deficiency anemia of kittens (5-10 weeks old; is transient
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