Diagnostic tests save pet lives

Modern medicine's advances help your vet


“Thumper is scratching herself raw and the stuff I bought at the pet store doesn’t help.”

“Major is limping and has trouble getting up in the morning.”

“Venus cries when she urinates and doesn’t have a good appetite.”

“Pepper vomited her breakfast and has been lethargic for the past few days.”

“Summer has diarrhea again!”

Most pet owners face these or similar symptoms during the life of a dog. The more dogs a family owns, the more opportunities for confronting a host of medical problems, minor and major, that can affect man’s best friend. Dog illnesses run the gamut from crippling hip dysplasia to heartworm infestation, from mild digestive upset to deadly cancer; and from minor muscle injuries to deafness, heart disease, and allergies.

When dealing with canine health problems, a dog owner’s best friend is a veterinarian. Animal doctors help pet owners through a myriad of mundane and catastrophic pet diseases and injuries, and they do so with the miracles of modern medicine at their fingertips.

When a sick pet arrives on the doorstep, a veterinarian has a battery of diagnostic tests to use depending on the symptoms. Major will likely get an x-ray and perhaps an ultra-sound of his sore leg; Thumper might get a skin biopsy; Venus will get a urinalysis and blood test; Pepper will have a blood chemistry screen and a complete blood count; and Summer will get a stool check for blood and parasites as well as a battery of blood tests.

Obviously, if a bone is broken or if arthritis is suspected, an x-ray is a useful diagnostic tool, but the connection between chemical tests performed on body fluids and identification of disease is a bit more mysterious. This brief look at blood, urine, and feces tests will help remove some of that mystery, but any questions about the value of particular tests for particular dogs should be asked when the dog, the owner, and the veterinarian are in the same room.

Complete blood count

The dog’s blood often tells the story of his illness. A complete blood count, or hemogram, includes a look at the numbers of red and white blood cells and tells the veterinarian whether a dog is anemic, has an infection, or has a clotting factor disease. Blood for the test is drawn into a tube that contains an anti-coagulant so the blood doesn’t clot.

The CBC includes a hematocrit or packed cell volume test that shows the relationship between the red cells and the blood plasma. A higher than normal packed cell volume may tell the vet that the animal is dehydrated or is experiencing a shock to his system; a lower than normal PCV indicates the dog is anemic.

The CBC also includes a description of any abnormalities in blood cell shapes, size, color, or appearance; an actual count of red cells in a microliter of blood; and an assessment of blood hemoglobin, the substance that carries oxygen throughout the bloodstream. In some anemias, a dog can have a normal number of red blood cells but lack sufficient hemoglobin to carry life-giving oxygen throughout the body.

The CBC also evaluates and counts the white blood cells – the body’s defense against infection. The ratio of one white blood cell for every 600-700 red blood cells is normal for dogs. An elevated white cell count indicates infection; a depressed white cell count indicates weakness from a long illness. Extreme stress can also impact the number of white blood cells.

There are five types of white blood cells divided into general categories – granulocytes and agranulocytes. The granulocytes include neutrophils, eocinophils, and basophils, all produced in the bone marrow along with red blood cells. These types of white blood cells attack and destroy disease-causing organisms.

Lymphocytes are agranulocytes produced in the lymph nodes and spleen. A decrease in lymphocyte numbers happens at the onset of infection or following the use of steroid medications. An increase in lymphocyte numbers may indicate prolonged illness or leukemia, a fatal type of cancer.

Monocytes, the final type of white blood cell, develop in both the spleen and the bone marrow. They attack infectious organisms and produce proteins that help heal injured tissue.

The platelet is the third type of blood cell examined in the CBC. Platelets help form clots so an animal does not bleed to death from a laceration.

When the veterinarian draws blood for a CBC, he generally sends it to a laboratory with the equipment and the technicians to run the tests and evaluate the results. Sometimes, the veterinarian has a diagnosis in mind and uses the test to confirm his suspicions, and sometimes the test provides valuable clues that allow a diagnosis to be made and treatment to begin. In either case, a CBC is an essential analytical tool.

Blood chemistry

A blood chemistry screening checks the fluid portion of the blood for levels of enzymes, sugar, nitrogen, minerals, proteins, and cholesterol that give clues to the health of kidneys, liver, heart, and muscles. Individual tests include blood glucose, blood urea nitrogen, creatinine, calcium, total protein, bilirubin, alkaline phosphatase, alanine amino transferase, cholesterol and sodium and potassium levels. The sample for these tests is allowed to clot; the cells are discarded and the tests are performed on the remaining serum.

The blood glucose (sugar) test is definitive in diagnosing diabetes (high blood sugar) and hypoglycemia (low blood sugar). Hypoglycemia can cause weakness, lack of coordination, and coma in young puppies, particularly toy breed puppies from six-to-12 weeks of age; in hunting dogs involved in long periods of strenuous activity; and in dogs with long-term illness.

The blood urea nitrogen test determines whether the kidneys are properly removing nitrogen wastes from the body. A high BUN count can indicate kidney disease, heart disease, or dehydration.

Creatinine is excreted by the kidneys; an increase in creatinine levels indicates kidney malfunction.

Changes in calcium levels in the blood can lead to heart and muscle disorders or can signal a case of eclampsia (milk fever), a condition of nursing mothers.

Total protein levels include measurement of albumin and globulins and indicate malnourishment or chronic infectious disease.

Bilirubin is a byproduct of hemoglobin breakdown. High bilirubin levels indicate an increase in red blood cell destruction or a diseased liver.

Alkaline phosphase is an enzyme that can become elevated in the presence of some types of cancer or some forms of muscle or liver disease.

An elevated value for the enzyme alanine amino transferase indicates a breakdown in liver function.

Although cholesterol level is not tied to coronary artery disease in dogs as it is in humans, an elevated cholesterol count can be an indicator of poor thyroid gland function.

Sodium and potassium levels are important measures of disease to the adrenal glands, heart, or kidney and can be influenced by some medications.

Disease organisms

Blood evaluations may also discover the presence of infectious disease organisms or parasites. Viruses such as distemper, infectious canine hepatitis, and neonatal canine herpesvirus infection can be discovered in blood tests. Lyme disease can be detected in a blood test by looking for antibodies to the bacteria rather than the disease organism itself. Heartworm infestations are discovered by checking a blood sample.


If Venus has trouble urinating, if there is blood in her urine, if her frequency of urination has increased or decreased, if her water consumption has changed, or if her urine smells foul, is bloody, or appears either very dark yellow or has no color at all, Mrs. Jones should make an appointment at the veterinary clinic as soon as possible, get a urine sample first thing in the morning, and hustle Venus into the car for the trip to the dog doctor.

The urinalysis is conducted in the clinic. The tests include a biochemical assay for blood, sugar, or proteins in the sample, a specific gravity test to measure concentration, and an examination of urine sediment for evidence of infection, cancer, or kidney disease.

In some cases, a veterinarian will need a urine sample directly from the bladder. If so, he can retrieve the sample by placing a catheter through the urethra into the bladder or inserting a needle through the lower abdominal wall directly into the bladder.

Leptospirosis, a disease that also infects people, can be detected in the urine.

Feces exams

Parasites and diseases affecting the intestines can be detected by examining a dog’s feces.

Fecal flotation tests identify the eggs of intestinal parasites such as hookworms, whipworms, and tapeworms. Organisms that cause diarrhea can also be shed in the feces, and examination of fecal material can discover the presence of intestinal bleeding and verify suspected problems with nutrient assimilation. Evidence of salmonella infection, campylobacteriosis, coronavirus, and other diseases that affect digestion can be found in the feces.

These are a few of the most commonly-used tests to aid the veterinarian in diagnosing canine illness. Although they increase the costs of care, they are vital elements in diagnosing disease and evaluating treatments. If you call the veterinary clinic with a report of pet illness and the doctor wants to see your dog before prescribing medication or asks for a urine or feces sample to aid in diagnosis, comply with the request – you pay for the doctor’s expertise and depend on him to fix your pet when she gets sick and an office examination and samples of body fluids and fecal material help him to help your pet.

Information for this article came from papers by Dr. Race Foster, Dr. Marty Smith, and Dr. Holly Frisby of the Foster & Smith Veterinary Services Department; the UC Davis Book of Dogs, edited by Mordecai Siegal; and the Dog Owner’s Home Veterinary Handbook by Delbert G. Carlson DVM, and James M. Griffin MD.

Norma Bennett Woolf

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