Many veterinarians recommend that senior dogs have complete physical examinations and tests twice a year. A comprehensive physical exam targets the dog's overall health by checking his weight, lymph nodes, skin, coat, lumps, bumps, heart/lungs, teeth, eyes, etc. etc. Blood chemistry tests evaluate the functionality of his organs and can detect conditions or diseases before symptoms emerge.

Understanding Blood Tests

CBC (Complete Blood Count)
The CBC evaluates red blood cells (RBCs), white blood cells (WBCs) and platelets and can indicate the presence of an infection or disease or a deficiency of red blood cells or platelets.

RBCs are important because they carry oxygen from the lungs to all body tissues. RBCs can be measured directly by counting them under a microscope or automatically with a specialized machine.

An indirect measurement of RBCs can be made by measuring the volume of red cells as a percent of the whole blood. This is called a hematocrit or packed cell volume (PCV). A low hematocrit and a low RBC count both indicate the presence of anemia. A high hematocrit can indicate dehydration.

WBCs are important for preventing and fighting infection. WBC numbers increase when the immune system is stimulated, such as an in an infection, parasitic disease and allergies. There are five types of WBCs. A CBC includes a count of total WBC number as well as a differential. A differential is a determination of the different types of WBCs.

Platelets are thin, disc-shaped cells. The platelet count is important because platelets play a crucial role in the clotting of blood, along with coagulation factors produced by the liver.

Blood Chemistry Panel/Profile
To evaluate how the body is functioning -- are the kidneys working, how is the liver, is the pancreas functioning normally -- a veterinarian will run a panel of tests which examine the proteins, enzymes and metabolic by-products in the blood plasma.

Kidney Function
Measurement of the creatinine and blood urea nitrogen (BUN) are used to evaluate kidney function. Concentrations of both creatinine and BUN are normally low. If the kidneys stop doing their job, both BUN and creatinine concentrations rise because the kidneys are unable to excrete them efficiently. This makes them good indicators of kidney function. Dietary phosphorus is excreted primarily by the kidneys. In patients with chronic kidney failure, phosphorus is not excreted properly and results in elevated phosphorus levels.

Liver Function
When the liver is sick or damaged, many of the enzymes that are normally inside cells are released into the bloodstream. Measurement of liver enzymes in blood can help a veterinarian determine the source and type of liver disease or blockage. These enzymes are: ALT, AST and ALP. The liver is involved in making bile. Bilirubin is the orange/yellow pigment in bile. Liver disease results in the release of large amounts of bilirubin into the bloodstream. This can result in jaundice.

Products made by a healthy liver, and therefore found in abnormally low levels if the liver is not functioning well include urea (BUN), cholesterol, albumin, globulins and glucose.

Pancreas Function
The pancreas gland releases hormones as well as some digestive enzymes. Pancreatitis may be indicated by the presence of pancreatic enzymes such as lipase and amylase in the bloodstream. Blood levels of these enzymes can be several times their normal level in patients with pancreatitis. Amylase can also be elevated during kidney diseases because kidneys are responsible for secreting amylase.

Thyroid Function
T4 (thyroxin), one of the hormones produced by the thyroid gland is usually present in diminished amounts in the blood of dogs with hypothyroidism (underactive thyroid glands). TSH thyroid stimulating hormone) is produced by the pituitary gland and is elevated in the blood of most dogs with hypothyroidism.