Blood Cells & Complete Blood Counts (CBC

Blood Cells & Complete Blood Counts (CBC) in Animals : 

Blood Cells & Complete Blood Counts (CBC) in Animals Dr.Kedar Karki

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A complete blood count is a count of the total number of cells in a given amount of blood, including the red and white blood cells; often referred to as a CBC, it is one of the most common tests done to check for abnormalities of the blood.

Components of Blood : 

Components of Blood Blood is made up of a liquid portion plus all the various blood cells. It functions to transport nutrients and oxygen to the cells; wastes and carbon dioxide to the organs responsible for their removal or breakdown; and also to defend the body against bacteria, viruses, and other organisms.

Components of Blood : 

Components of Blood The liquid portion of blood is referred to as plasma, if the blood was not allowed to clot, and serum, if it was. This liquid portion, without the cells, is generally a straw or light yellow color. The liquid portion of the blood is used in the chemistry tests.

Components of Blood : 

Components of Blood Every drop of blood literally contains millions of blood cells. Although the sample drawn for a CBC may seem small, it contains such huge numbers of cells that it is an excellent and accurate portrayal of the total numbers of these cells found in the bloodstream. The CBC is concerned with the quantities and types of red blood cells, white blood cells, and platelets.

Red Blood Cells : 

Red Blood Cells RBC's are formed in the bone marrow. The bone marrow constantly produces new RBC's, since the life span of an RBC is only about 120 days. The body can respond quickly to maintain the number of RBC's present in the blood vessels. The body measures their numbers simply by evaluating the quantity of oxygen being supplied to its tissues. If not enough oxygen is available, then the body sees that as a need for more working RBC’s.

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Hematocrit: In the CBC, we determine the number of RBC’s in several different ways. The quickest and easiest is called the hematocrit, also referred to as the packed cell volume (PCV). A blood sample is placed in a tiny glass tube and spun in a centrifuge. This device spins the tube round and round at several thousand revolutions per minute. The cells are heavier than the plasma and are compacted at one end of the tube. After the tube is spun, it is examined and the PCV is determined as the percentage of the cellular portion relative to the total amount of blood in the tube (i.e., remainder being the plasma). The normal for dogs is 40-59 and cats is 29-50.

Red Blood Cell Count: : 

Red Blood Cell Count: The actual number of RBC's in a given quantity of blood. This is called the 'red count,' and is more difficult to perform than a hematocrit. The red blood cell count is not measured as a percentage of anything, but rather the actual number of cells found in a microliter (µ l). To put things into perspective for those of us who do not relish the metric system, a liter is just a little larger than a quart, and a microliter is one millionth of a liter. Each laboratory has their own set of 'normal' ranges for a RBC count, but the average is 5.6-8.7 x 106 RBC's per microliter for dogs, and 6.1-11.9 x 106/µ l for cats.

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Hemoglobin: A final way we can evaluate the RBC's is by quantifying the amount of hemoglobin present. In some anemias, the actual number of RBC's may not be real low, but if the cells contain less than the normal amount of hemoglobin, the signs of anemia could be quite severe. The normal hemoglobin level for a dog is 14-20 grams/deciliter, and 9-15.6 g/dl for cats.

White Blood Cells : 

White Blood Cells The other major type of blood cells are the white blood cells (WBC’s), which are also referred to as leukocytes. There are different types of leukocytes, and a white blood count (WBC) is a total of all the various kinds. The normal range for a WBC count in the dog would be between 6,000 and 17,000 per microliter, and in the cat, 4,900-20,000/µ l.

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The number of WBC's is typically elevated when the body is fighting a severe infection or stressed by metabolic toxins (a patient that was in acute kidney failure with waste products building up in its body would normally have an elevated WBC).

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The WBC count will be lower than normal, if an animal has been weakened from a prolonged, debilitating disease and in some viral infections.

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WBC’s are divided into two groups depending on how they react to the stains that are used to better observe them under a microscope. There are granulocytes (they are WBC's with granules that absorb the stain) and the agranulocytes (those that do not absorb the stain).

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The granulocytes include the neutrophils, eosinophils, and the basophils, while the agranulocytes are the lymphocytes and monocytes.

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Neutrophils: Neutrophils are also formed in the bone marrow. Mature cells have a multi-lobed nucleus and are referred to as 'segmented cells' (sometimes called 'segs'), while the immature ones have a single-lobed nucleus and are referred to as 'bands.'

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These cells function by actually engulfing disease-causing bacteria and other small particles. In the presence of a bacterial infection, their number in the peripheral blood increases,

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The normal range for mature neutrophils is between 3,000 to 12,000/µ l. The normal for the bands is approximately 100 to 300 per microliter.

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When total neutrophil numbers are increased, it is usually a sign of a bacterial infection or some form of extreme stress. In most viral infections, the total number of neutrophils decreases.

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Eosinophils: Eosinophils are normally seen in fewer numbers than neutrophils. They are also produced in the bone marrow and their normal range is about 100 to 1200 per microliter. They also have the ability to eat up or engulf foreign particles into their bodies.

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quantities increase in the circulating blood when the animal is suffering from an infection with parasites, or has allergies. In conditions that cause extreme or prolonged stress to the dog or cat, eosinophil numbers decrease.

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Basophils: The last of the granulocytes is the basophil. These are the least common of all the WBC’s. In many samples, none are present. Their function is unknown, but they are also produced with the bone marrow.

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Lymphocytes: Of the agranulocytes, the most abundant is the lymphocyte. There are normally 500-4,800 of these in a microliter of dog's blood, and 1,500-7,000/µ l in a cat's. They are formed and released from lymphoid tissue such as lymph nodes, spleen, etc.

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When lymphocytes numbers decrease it is referred to as a lymphopenia, and is frequently noted in the initial stages of infections (a common example would be parvovirus) or following the use of corticosteroids like prednisone. There

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An increase in the number of lymphocytes does not happen as consistently as might be expected, but is noted in prolonged illnesses. Examples of this would be when bacterial or viral infections have gone on for a long time or in certain autoimmune diseases. A common cause of increased lymphocytes is leukemia, which is a cancer of blood cell production that is usually fatal.

Monocytes: : 

Monocytes: Monocytes develop and are stored in the spleen and bone marrow. Normally, there are only 100 to 1800 of these per each microliter of dog's blood, and 0-850/µ l in a cat. They also have the ability to eat or engulf foreign material, such as infectious organisms. Additionally, they secrete various protein molecules that help in the clean up of inflamed and irritated tissue. Their numbers do not vary greatly unless there is a cancerous leukemia condition affecting their cell lines.

Platelets : 

Platelets The platelets and a protein called fibrinogen are responsible for the repair of all damaged blood vessels

Cell Morphology : 

Cell Morphology

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Normal Hematology Values for Dogs and Cats* * normal values may differ from laboratory to laboratory.