Whether a veterinarian is faced with an ill patient or is simply monitoring an elderly patient, he or she wants to know how the body is functioning: Are the kidneys working? How is the liver? Is the pancreas functioning normally? To evaluate these organs, a veterinarian may run a general panel of tests called a blood chemistry profile, which examines the proteins, enzymes, and metabolic by-products in the blood. The tests included in each profile vary from laboratory to laboratory, but these common blood tests evaluate organ function, electrolyte status, hormone levels, and more. They are important in evaluating older pets, pets with vomiting and diarrhea or toxin exposure, pets receiving long-term medications, and general health prior to anesthesia.
Today, many veterinarians have machines that perform some of these basic tests right in the office. More complicated tests must be sent to specialized laboratories. The following tests are used to assess kidney, liver, pancreas, and thyroid function: Albumin (ALB) is the most abundant protein in normal plasma. It is used to evaluate hydration, hemorrhage, and intestinal, liver, and kidney disease.
Alkaline Phosphatase (ALKP) is an enzyme present in liver, kidney, bone, and intestine. Elevations of this enzyme may indicate liver damage, Cushing's disease, active bone growth in young pets, or bone cancer. Elevations in this test are especially significant in cats. Alanine aminotransferase (ALT) is an enzyme involved in forming amino acids. It is found primarily in the liver. Measurement of ALT is used to measure active liver damage, but elevations of this enzyme do not indicate the cause. Measurement of the enzyme Amylase (AMYL) is usually used to evaluate the pancreas, and elevations indicate pancreatitis or kidney disease. Bilirubin is the orange-yellow pigment in bile and is formed by the breakdown of hemoglobin in red blood cells. Increased amounts of bilirubin occur during liver failure and some blood diseases. It is this increased bilirubin that gives the yellowish appearance of jaundice. Elevated levels of total bilirubin (TBIL) may indicate liver or blood disease. This test helps identify bile duct problems and certain types of anemia. Blood Urea Nitrogen (BUN) is a measurement of non-protein nitrogen. It is useful in evaluating kidney function, dehydration, and urinary tract obstruction. An increased blood level of BUN is called azotemia and can be caused by kidney, liver, and heart disease, urethral obstruction, shock, and dehydration. Calcium (Ca) is an abundant mineral element found primarily in the skeleton. It plays an important role in many organs and muscle. Blood levels can be altered in diseases of the parathyroid gland, kidney, and bone. Tumors, hyperparathyroidism, kidney disease, and low albumin are just a few of the conditions that alter serum calcium. Cholesterol (CHOL) in pets is used to supplement the diagnosis of hypothyroidism, liver disease, Cushing's disease, and diabetes mellitus. Plasma concentrations of the electrolyte Chloride (Cl) are altered in certain kidney diseases, gastrointestinal problems, and adrenal malfunction. Chloride is often lost with vomiting and Addison's disease. Elevations can also indicate dehydration. Creatinine (CREA), like BUN, is used to evaluate kidney function. It is considered a much better measurement than BUN because it is less influenced by diet and other factors. An elevated creatinine indicates kidney failure and helps distinguish between kidney and non-kidney causes of an elevated BUN. Glucose (GLU) or blood sugar concentrations can be altered in diseases of the pancreas such as diabetes, as well as the adrenal and pituitary glands. Elevated levels may indicate diabetes mellitus, whereas low levels can cause collapse, seizures, or coma. A cat's glucose level can be elevated if it is very scared when the blood is drawn.
Potassium (K) is an electrolyte that is present at high concentrations inside cells. It is lost with vomiting, diarrhea, or excessive urination. Increased levels may indicate kidney failure, Addison's disease, dehydration, and urethral obstruction. High levels can lead to cardiac arrest. The majority of the electrolyte Phosphorus (PHOS) is present in bone. The small intestine, kidney ,and skeleton are all involved in maintaining levels of phosphorus. Concentrations are often elevated during kidney failure, hyperthyroidism, and bleeding disorders. Sodium (Na) is intricately involved in water balance. Concentrations of sodium can vary due to a variety of drugs and diseases. It is lost with vomiting, diarrhea, and kidney and Addison's disease. This test helps indicate hydration status. Total protein (TP) indicates hydration status and provides additional information about the liver, kidneys, and infectious diseases. Thyroxine (T4) is a hormone produced by the thyroid gland. Concentrations will be altered in various forms of thyroid disease. Decreased levels often signal hypothyroidism in dogs, whereas high levels indicate hyperthyroidism in cats. Free T4 is a measurement of the fraction of hormone not bound to proteins in the blood.
The tests listed above are the most common ones that your veterinarian will use to assess your pet's health. However, for any given disorder there may be more specific tests your veterinarian may need to perform to properly diagnose your pet's condition. All pets over 8-10 years of age (this may vary from clinic to clinic) should have bloodwork yearly along with their regular physical examination. It is also important to have bloodwork evaluated prior to any anesthetic procedure. Understanding the tests performed on your pet will help you better understand any illnesses detected and enable you to work with your veterinarian to make decisions about your pet's treatment.