UNDERSTANDING YOUR PET’S BLOOD, TISSUE & URINE LABORATORY RESULTS

Blood and urine tests help determine causes of illness accurately, safely, and quickly allow us to monitor the progress of case management and medical treatments.

This guide can help you understand your pet’s laboratory diagnostic test results. Proper communication with your veterinarian is essential regarding interpretation of any lab results. Normal reference laboratory ranges are not provided here, as these may vary depending upon the type of instrumentation and reagents used. Each veterinary diagnostic laboratory or in-clinic diagnostic test machine comes with its own normal reference ranges.

Complete Blood Count (CBC)

A CBC gives information on hydration status, anemia, infection, the blood’s clotting ability (platelet count), and the ability of the immune system (white blood cells) to respond to a stress or other disease event. This test is important for pets with fevers, vomiting, weakness, pale gums, or loss of appetite. If your pet needs surgery, a CBC may detect a potential bleeding disorder or other unseen abnormalities.

Hematocrit (HCT, PCV)measures the percentage of red blood cells in the sample to detect conditions such as anemia and dehydration.

Hemoglobin (HGB)and mean corpuscular hemoglobin concentration (MCHC) measures the oxygen-carrying pigments of red blood cells.

White blood cell (WBC)or leukocyte count measures the body’s ability to respond to stress or a variety of conditions.  Increases or decreases indicate certain diseases or infections.

Granulocytes(neutrophils; PMNs),lymphocytes and monocytesare specific types of white blood cells.

Eosinophilsare another specific type of white blood cell that may indicate allergic or parasitic conditions.

Platelet countmeasures the tiny cells that help form blood clots.

Reticulocytesandnucleated red blood cellsare immature red blood cells. High levels indicate a regenerative anemia.

Serum Blood Chemistries

These tests evaluate organ function, electrolyte status, and hormone levels. They also give barometers of adrenal function and other diseases. We use these tests for base lines as pets age, pre-anesthetic evaluation, monitoring long term medications, as well as evaluating sick animals.

Albumin(ALB) is an important serum protein that helps evaluate hydration, presence of blood loss from hemorrhage, and intestinal, liver, and kidney disease. It maintains the oncotic pressure that keeps the fluid within the blood vessels rather than allowing it to leak out into the tissues.

Alkaline phosphatase(ALK P) elevations may indicate liver damage, Cushing’s disease (overactive adrenal function), arthritis, and active bone growth in young pets. Levels rise slightly as animals age. This test is especially significant in cats as even slight elevations may indicate of liver disease.

Alanine aminotransferase(ALT, SGPT) is an indicator of active liver cell damage but does not identify the underlying cause. Liver cleansing herbs such as milk thistle or SAMe are used along with a grain-free liver sparing diet, once more definitive diagnostics are completed.

Amylase(AMYL) elevations show pancreatitis, when the serum lipase is also high, or become increased in the presence of kidney disease.

Aspartate aminotransferase (AST, SGOT) increases may indicate liver, heart, or skeletal muscle damage, but this is an enzyme released from many injured cells.

Blood urea nitrogen(BUN) indicates the amount of protein nitrogen in the blood and usually reflects kidney function. An increased blood level is called azotemia and may be caused by kidney, liver, heart disease, urethral obstruction, shock, dehydration, impaired intestinal food absorption, or an intestinal or stomach foreign body. A low BUN may indicate a cirrhotic liver or portal caval liver shunt. It can be elevated normally as a result of eating a raw diet.

Calcium(CA) deviations may indicate a variety of diseases. Cancers, kidney disease, hyperparathyroidism, and anal gland tumor, are just a few of the diseases that alter calcium levels. In dogs, but not cats, the calcium concentration is corrected upwards when the albumin level is below 3.5 mg/dl. The result is the corrected calcium.

Cholesterol(CHOL) may be altered in hypothyroidism, liver disease, Cushing’s disease, high fat diets, and diabetes mellitus.

Chloride(CL) is an electrolyte often lost with vomiting and in Addison’s disease (underactive adrenal function). Elevations may indicate dehydration.

Cortisolis a hormone released in pulsatile fashion from the adrenal glands in response to stress or certain adrenal diseases. More specific, dynamic diagnostic tests of adrenal function include the ACTH stimulation test, low-dose dexamethasone suppression test, and urine cortisol-creatinine ratio.

Creatinine level reflects kidney function. This test helps distinguish between kidney (renal) and non-renal causes of an elevated BUN.

Gamma glutamyl transferase(GGPT) is an enzyme that specifically measures bile flow through the liver. Stasis of bile flow is seen in liver or gall bladder disease and in corticosteroid excess.

Globulinlevel reflects all the blood proteins other than albumin, and typically increases with chronic inflammation and certain diseases such as feline infectious peritonitis (FIP). Low levels are seen in the very young and in immune deficiency states.

Glucoseis a blood sugar. Elevated levels may indicate diabetes mellitus (cats, dogs). Low levels can cause fainting, collapse, seizures, or coma.

Potassium(K) is an electrolyte lost with vomiting, diarrhea, or excessive urination. Increased levels may indicate kidney failure, Addison’s disease, dehydration, and urethral obstruction. High levels are normal in the Japanese dog breeds because of their unique red blood cell membrane. In disease states, high levels can lead to cardiac arrest. Low levels may occur with loss of appetite especially in cats.

Lipaseis an enzyme that may indicate pancreatitis, when the serum amylase is also elevated.

Sodium(NA) is an electrolyte lost with vomiting, diarrhea, kidney disorders, and Addison’s disease. This test helps indicate hydration status.

Phosphorus (Phos) elevations are often associated with kidney disease, hyperthyroidism, and some bleeding disorders.

Bilirubinelevations may indicate liver, gall bladder, or hemolytic diseases.

Total protein indicates hydration status and provides additional information about the liver, intestine, kidneys, and presence of infection.

Thyroid tests (T4, FreeT4, T3, FreeT3, TSH, and TgAA) are performed to measure thyroid function. A complete thyroid antibody profile is much preferred over a simple total T4 test, which can be misleading. Age- and breed-specific normal ranges should be taken into account. Genetic screening of dogs intended for breeding is important, as up to 90% of canine thyroid disease is due to heritable autoimmune thyroiditis. Dogs testing positive for this heritable disorder need to be treated with thyroid hormone and should not be used for breeding purposes. Decreased levels may signal hypothyroidism, non-thyroidal illness or use of certain drugs, while high levels indicate hyperthyroidism in older cats, and may also occur from eating the throat or gullet part of red raw meat and in thyroid tumors.

TLI, B12, Folateare intestinal tests to indicate malfunction of the digestive tract of cats and dogs.

Bile Acidsare measured as a specific test for liver function, including congenital liver shunts (portacaval shunts, microvascular dysplasia), cirrhosis, and active liver disease. They can also be measured in urine.

Urinalysis (UA)

Evaluates kidney function, bladder pathology including tumors, urinary tract infections, urine concentration, presence of bladder stones and crystals.

Urine-Cortisol Creatinine Ratio(UCCR) is a simple screening test for Cushing’s disease. Must be performed on urine collected at home, first thing in the morning and before exercise.

Urine-Protein Creatinine Ratio(UPCR) measures kidney function and is abnormal in kidney failure.

Other Diagnostics

Cytologyis performed by a pathologist looking at a tissue or body fluid sample for evidence of any abnormality.

Culture and Sensitivityis measured on a body discharge or urine sample to determine the type of bacteria or fungus present, and the best antibiotic or antifungal drug to treat the condition.

Biopsy is a sample of tissue sent to a pathology laboratory for analysis. Histopathology is performed on specially prepared stained or frozen sections of the tissue to identify any abnormality.

Fecal exams analyze for intestinal parasites of various types.

It is important to remember that not all elevations may be significant. Laboratory tests are tools for assisting with the potential diagnosis of a medical condition or illness. Which is why it is important that your Veterinarian use the findings of the laboratory results in conjunction with symptomatology, the outcomes from the physical exams and other diagnostics tests (as applicable), before the diagnosis of a condition can be reached.

Reprinted with permission from Jean Dodd’s DVM:  http://drjeandoddspethealthresource.tumblr.com/post/116836320986/pet-laboratory-results#.WMgp3TvyuUk  

This article has been amended to include additional supporting information.

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