Blood Count and Urinalysis for Dogs
At some time in your dog's life, it is highly likely that laboratory tests will be performed. These can range from very simple tests, such as fecal checks for parasites or heartworm tests looking for antigens, to sophisticated bloodwork checking out various organs and their functioning. The most common tests done to the blood and urine are discussed here. Blood samples are normally taken from your dog's vein-either a leg or the jugular vein in the neck. Fasting is recommended before blood tests.
Complete Blood Count (CBC) or Hemogram
A CBC is done on blood taken directly from your dog's vein. The goal is to count the different types of cells present in your dog's blood. At the same time, an evaluation is made about the types of cells and their health and life stages. Blood counts may be lowered overall in dogs with bone marrow disorders and those undergoing certain types of chemotherapy.
PCV or Hematocrit:
This test checks to see approximately how many red blood cells your dog has. Blood in a tiny tube is spun in a centrifuge and the number of red blood cells is given as a percent of the total blood volume. Normal dogs run about 35 to 50 percent. A low PCV indicates anemia, which could have a number of causes from hemorrhage to liver or kidney disease. A high PCV is often present in dogs who are dehydrated.
With the red blood cells (RBC), an actual count is made by estimating from the number of cells spread on a slide and examined under a microscope. The amount of hemoglobin present and the age and size of the red blood cells are also measured. MCV is mean corpuscular volume, which is the average size of the red blood cells. MCH is mean corpuscular hemoglobin (the substance in the red blood cells that transports oxygen), which is the average amount of hemoglobin inside a red blood cell. MCHC is the mean corpuscular hemoglobin concentration, which is the average concentration of hemoglobin in the red blood cells, expressed as a percentage. Your veterinarian or the laboratory technician will also examine cells for maturity and for any blood-borne parasites.
An estimate will also be made of the total number of white blood cells (WBC) in the sample. White blood cells include eosinophils (cells that fight parasite infestations and are involved in allergies), and cells that fight infections or cellular invaders, including neutrophils, lymphocytes, basophils, and monocytes. The number of white blood cells such as lymphocytes may be increased in dogs with certain cancers, as well. Normally, white blood cell counts rise with bacterial infections, but if the infection is winning the battle, counts may be lower than expected. Viruses may also lower the white blood cell count.
Platelets are cells that assist in clotting and coagulation. An estimate of their numbers is also made from a blood sample on a slide examined under a microscope. Platelets can be low in number in dogs with certain immune disorders, some cancers, and bleeding disorders. Some breeds, such as Cavalier King Charles Spaniels, can have platelet anomalies that cause their numbers to be low.
Urinalysis involves looking at a urine specimen. Urine samples may be collected as a “free catch” when the dog is voiding or by using a catheter or a needle inserted directly into the bladder. The last two methods are much better if an infection is suspected, because the sample collected is sterile and any bacteria cultured from it is likely to be the culprit.
The urine is checked for certain components, such as glucose and pH. Concentration and the presence of any cells are also evaluated. Some of this is done with a specially coated test strip that gives a range for results and some is done with special instruments.
Dilute urine may mean kidney problems or increased drinking. Concentrated urine could mean dehydration or liver or kidney problems.
The urine is checked for glucose, indicating diabetes mellitus, and for protein, indicating kidney damage. The pH will tell if the urine is acidic or alkaline, which can be influenced by diet and may cause bladder crystals or stones to form.
The urine is also spun in a centrifuge and the cells collected and examined. The presence of red blood cells or white blood cells may indicate infections or damage to the urinary tract. Crystals suggest stone formation. Bacteria can indicate infection, in which case the sample may also be cultured to look for bacterial infections.
This article is excerpted from “Dog Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.
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