Lymphocytes also help fight infection and produce antibodies against infectious agents (viruses,
bacteria, etc.). Lymphocytes may be increased in puppies and kittens with an infection, they can
be decreased in pets who are severely stressed, and lymphocytes might be lost in some types of
diarrhea. Certain drugs, such as prednisone (a cortisone-type drug) will decrease the number of
lymphocytes in the blood stream.
Monocytes may be increased in pets with chronic infections. Eosinophils and basophils are
increased in pets with allergic diseases, or parasitic infections (worms, fleas, etc.).
Platelets are produced in the bone marrow and are involved in the process of making a blood
clot. Platelets live a few weeks and are constantly being produced by the bone marrow. Low
platelet counts occur if the bone marrow is damaged and doesn’t produce them, or if the
platelets are destroyed at a faster rate than normal. The two primary causes of platelet
destruction are immune-mediated destruction (ITP or IMT) and DIC (disseminated intravascular
coagulation). Immune-mediated thrombocytopenia happens when the animal’s immune
system destroys platelets. DIC is a complex problem in which blood clots form in the body using
the platelets faster than the bone marrow can produce new ones. Animals with a low platelet
count bruise easily and may have blood in their urine or stool.
Packed cell volume (PCV) (called hematocrit, HCT, in humans) is another measure of red blood
cells. A small amount of blood is placed in a tiny glass tube and spun in a centrifuge. The blood
cells pack to the bottom of the tube and the fluid floats on top. The PCV is the percent of blood,
that is cells, compared to the total volume of blood. In normal dogs and cats, 40-50% of the
blood is made up of blood cells and the remainder is fluid.
Blood and urine tests are performed to get an initial overview of the health, and sometimes the
function, of body organs. Some blood tests are very specific for a single organ, whereas other
tests are affected by several organs. Blood tests are often performed as a biochemistry profile,
or chemistry panel, which is a collection of blood tests to screen several organs at one time. The
makeup of a biochemical profile varies with the laboratory in which it is performed. Following
are some of the more commonly performed chemical tests:
Albumin is a small protein produced by the liver. Albumin acts as a sponge to hold water in the
blood vessels. When blood albumin is decreased, the pressure created by the heart forcing
blood through the blood vessels causes fluid to leak out of the blood vessels and accumulate in
body cavities such as the abdominal cavity or in tissues as edema. Albumin is decreased if the
liver is damaged and cannot produce an adequate amount of albumin or if albumin is lost
through damaged intestine or in the urine due to kidney disease. The only cause of increased
albumin is dehydration.
Alkaline phosphatase originates from many tissues in the body. When alkaline phosphatase is
increased in the bloodstream of a dog the most common causes are liver disease, bone disease
or increased blood cortisol either because prednisone or similar drug is being given to the pet
or because the animal has Cushing's disease (hyperadrenocorticism). In cats, the most common
causes of increased alkaline phosphatase are liver and bone disease.