CLINICAL PATHOLOGY

Clinical Textbook for Veterinary Technicians by Dennis M. Mccurnin 4 th edition Saunders

Accurate clinical pathology data is invaluable in the diagnosis of diseases in all species.

Repetition of the data (tests) provides a means of monitoring and evaluating the success of chosen treatments.

The most commonly used clinical laboratory procedures in veterinary practices are

hematologyurinalysisclinical chemistry cytology

Hematology

Hem(e) = bloodOlogy = study of

Hematology = study of blood

CBC = complete blood countProvides the veterinarian with the following information

* PCV (packed cell volume)* WBC count (leukocytes)* RBC count (erythrocytes)* hemoglobin* RBC indices* total plasma protein* evaluation of the blood smear for RBC morphology and WBC differential

Hematological procedures are performed on anticoagulated whole blood.

The preferred anticoagulant is EDTA and is commercially available in “purple top” tubes.

Equipment: microscope microhematocrit centrifuge (to determine PCV)refractometer (determine the plasma protein and

urine specific gravity)hemacytometer (counting chamber)

Erythrocytes

PCV = percentage of total blood volume accounted for by RBCs* hematocrit

RBC indicies = calculations provided when automated analyzers are used.

MCV = mean corpuscular volumeMCH = mean corpuscular hemoglobinMCHC = mean corpuscular hemoglobin concentration

* Could be used to help evaluate and determine causes of anemia.

The erythrocytes of most mammals are disc shaped and anuclear.

They appear flat with an area in the center of the cell with less hemoglobin.

The RBCs of animals differ in size. From largest to smallest: dog

horse cow

cat sheep goat

* Anisocytosis = RBCs that vary in size (cows more than other species)

•Poikilocytosis = term used to indicate changes in RBC shape

•Leptocytes = RBCs with an increased surface area that makes them highly deformable. (Target Cells)

•Acanthocytes = RBCs with a membrane abnormality that causes the cells to develop multiple, irregularly spaced club shaped projections.

•Crenated cells = cells which have numerous rounded, evenly spaced projections

•Schisotcytes = fragmented RBCs

•Spherocytes = RBCs that appear smaller than normal and show no central pallor

•Schisotcytes = fragmented RBCs

•Spherocytes = RBCs that appear smaller than normal RBCs and exhibit no central pallor

* Metarubricyte (NRBC) = immature nucelated RBCs

•Polychromasia = term used to describe a variation in the color of RBCs.

•Polychromatophilic = bluish in color when stained

•Hypochromic RBCs = have an increased area of central pallor with a narrow, peripheral rim of hemoglobin within the cell.

* Rouleaux – groupings of RBCs that resemble stacked coins (it is important to establish this from true agglutination)

Possible Parasites in RBCs:

* Haemobartonella felis – the parasite responsible for the feline infectious anemia.

•Babesia spp. – various species that can infect any domestic animal

Other Morphological Abnormalities

•Howell-Jolley bodies – small, often singular, deeply basophilic nuclear remnants that are occasionally seen on normal blood films - can be seen with regenerative anemias.

•Basophilic stippling: is due to staining of small amounts of cytoplasmic RNA in RBCs. They can be found in markedly regenerative anemia in dogs and cats but most commonly in cattle

•Heinz bodies: denatured hemoglobin that has fused to the RBC membrande and appear as refractile projections from the RBC cell membrane.