THE BLOODY TRUTH ABOUT CATS AND DOGSHEMATOLOGY BASICS: DIFFERENTIALS

Sarah Ouellette CVT.

THE WHITE BLOOD CELL:LEUKOCYTES

White Blood Cells

• Five major White Blood Cells• Further defined into two groups:

1. Granulocytes• Neutrophils• Eosinophils• Basophils

2. Monocellular cells (agranulocytes)• Lymphocytes • Monocytes

White Blood Cells

• Granulocytes:• Classified due to the granules present in their cytoplasm

• Monocellular cells (agranulocytes):• Classified due to their round globular shaped nucleus

** somewhat misleading due to the fact that most monocytes do not have a round nucleus**

Granulocytes

• Neutrophils (segmented neutrophils, segs)• Most predominant WBC in healthy animals• First line of defense against infections• 1 ½ times the size of RBC’s

• Function:• Seek out, ingesting, killing, and invading

microorganisms

Neutrophils

Morphology:• Canine: white cytoplasm with sm. pink granules, multi-lobed nuclei with condensed chromatin that stains deep purple

Neutrophils

Morphology:• Feline: white/pink cytoplasm witch lacks visible granules, multi-lobed nuclei with condensed chromatin that stains deep purple

Granulocytes

• Eosinophils• Second most common granulocyte• Slightly larger than neutrophils

• Function:• Hypersensitivity reactions• Parasitic infections• Allergic reactions

Eosinophils

Morphology:• Canine: variable in size, round-oval in shape. The cytoplasm is faint blue/pink that contains round pink-orange granules, lobed nuclei with condensed chromatin (less lobed than neutrophils)

Eosinophils

Morphology:• Feline: uniform in size and shape. The cytoplasm is faint blue/pink that contains rod shaped pink-lavender granules, lobed nuclei with condensed chromatin (less lobed than neutrophils)

Eosinophils

• A specific morphologic variant of the eosinophil is seen in greyhounds and other sighthounds

• Lack visible granules and appear as cells with slightly segmented nuclei, grey/lavender cytoplasm, and vacuoles.

Granulocytes

• Basophils• Occasionally observed/difficult to find• Slt larger than neutrophils• Commonly mistaken for monocytes

• Function:• Hypersensitivity reactions• Parasitic infections• Allergic reactions

Basophils

Morphology:• Nucleus is segmented with dense chromatin

• Can also commonly have a kidney bean shaped nucleus

• Cytoplasm is pale blue/grey/lavender • Contains a few distinct dark blue/purple granules• Distinct “cobblestone” appearance• Cytoplasm MAY contain small vacuoles

• Most commonly confused with monocytes

Basophils

• Canine • Feline

Monocellular cells

• Lymphocytes• Second most common WBC seen• Slightly larger than red blood cells• Commonly confused with nRBC

• Function:• Antibody immunity• Cell mediated immunity

Lymphocytes

Morphology:• Small amount of light blue cytoplasm • Coarsely clumped chromatin

• takes up the majority of the cell

• Nucleus is round-oval in shape • may be slightly indented

nRBC v.s lymphocytes

• nRBC • lymphocyte

Lymphocytes

Monocellular cells

• Monocytes• Largest WBC• Increased # indicative of chronic inflammation

• Function:• Phagocytosis• Release inflammatory mediators

Monocytes

Morphology:• Variable in shape from round to angular • Grey/blue cytoplasm• Nucleus is irregular and variable in shape

• and has a lacey less dense chromatin pattern

• May have a few small vacuoles

(not distinguishing factor)*

Monocytes

• Canine

Monocytes

• Feline

Immature WBC

Left shift• Increased numbers of immature neutrophils• Most common cause is inflammation • Can also be seen in some marrow disorders (leukemia) or severe bone marrow injury

• Cells are classified based

on their stage of maturation

Immature WBC (neutrophils)

• Shape of the nucleus differentiates these cells

• Myelocyte – nucleus appears round• Metamylocyte – kidney bean shape• Band cell- horseshoe shape• Mature cell – segmented

Immature WBC

• Band cells• Widths of the nuclear margins

are smooth and parallel

Toxic changes

• Hypersegmentation• Neutrophil with 5 or more lobes

• Causes:

• Common ageing artifact• Exposure to excessive amounts of EDTA

• Also seen in:• Glucocorticoid therapy• Hyperadrenocorticism• Chronic infections

Toxic Changes

Toxic Neutrophils• Occurs when the maturation in the bone marrow is

accelerated• Often accompanied by a left shift

• Causes:• Inflammation

• Graded as mild, moderate and severe• Severity of abnormalities and number of cells affected

• We evaluate five main features to determine toxicity…

Toxic changes

1. Cytoplasmic basophillia - cytoplasm develops a streaky irregular darker blue appearance

2. Presence of dohle bodies

3. Cytoplasmic vacuolation - vacuoles are present within the cytoplasm of the cell giving it a frothy appearance

• Vacuolation can also be a storage related artifact

4. Nuclear immaturity - nuclear chromatin is lighter, finer and less clumped than that of normal cells

• often subtle and difficult to visualize

5. Toxic granules – distinct fine granules in the cytoplasm • change is not common and can be difficult to visualize

Toxic Changes (Neutrophil)A: Normally matured segmented

C: late band neutrophil

Both: white cytoplasm with pink granules

long and fairly narrow nuclei

tightly condensed chromatin

B: Segmented

D: Band neutrophil

Both: with toxic changes

Nucleus is larger

less condensed chromatin

bluer cytoplasm due to retention of ribosomal RNA

Toxic Changes

Reactive Lymphocytes • Large lymphocytes

• Seen in:• Antigenic stimulation

• Relatively non-specific finding • Any disease process can cause an antigenic stimulation leading to the presence of these cells in circulation

Toxic Changes

Reactive Lymphocytes • Extremely variable in size and morphologic features• Chromatin is coarsely clumped • Nucleus is extremely variable in shape• Can have an increased amount of cytoplasm• Cytoplasm stains deep blue/purple

Toxic Changes

Granular lymphocytes • Usually found in low numbers in healthy animals• Caused by chronic antigenic stimulation

• Distinguished by the presence of distinct pink granules collected into one area of the cytoplasm

Abnormal WBC

• Mast cells• Rarely seen in peripheral blood smears• Large irregular deeply staining• Round/oval nucleus difficult to visualize• Large amounts of deep blue cytoplasm • Numerous small purple cytoplasmic granules

• Seen in:• Inflammatory diseases• Certain neoplastic diseases

Abnormal WBC

• Smudge Cells or Blast cells• Dying WBC’s• Normal to see an occasional cell• Increased numbers are indicative of leukemia

• May be an artifact of slide preparation• By applying too much pressure to the slide

Abnormal WBC

• Pelger-huet anomaly• Congenital disorder in dogs• All the granulocyte nuclei fail to undergo segmentation • Can also occur in certain drug interactions

Morphology:• Nucleus is uniform • Lacks the toxic changes

• distinguishes this from an inflammatory process

• Accompanied by a normal leukogram• Neutrophils have a normal function

Pelger-huet anomaly

WBC Inclusions

• Usually include or represent phagocytosed material such as other cells, cell debris, retained cellular material and infectious organisms

WBC Inclusions

• Chediak Higashi Syndrome• Syndrome of cats (Persians)• Neutrophillic inclusion• Variable size• Round, pale blue/pink• Attaches to granules in cytoplasm• Usually see 1:3 ratio

• Tend to have lower platelet numbers• Otherwise healthy

WBC Inclusions

• Barr body• Found in neutrophils• Appendage attached to nucleus• Small tennis racket shape• No pathological significance

• Indicates that the dog is female

WBC Inclusions

• Dohle Body• Small irregular pale blue aggregate • Present in cytoplasm of neutrophils• Represents aggregates of the rough endoplasmic reticulum

• Seen in toxic changes

WBC Inclusion

• Distemper virus• Aggregates of viral particles • Round and variable in size• Pink/lavender in color • Found in RBC,WBC• Rarely seen even with + infection

WBC Parasites

• There are several organisms that can be detected from examination of a peripheral blood smear, however they can be intermittently seen and therefor further serological testing should be done

• Transmission most commonly occur through the bites of ticks

WBC Parasites

Hepatozoon canis• Protozoal parasite transmitted via ticks• Not commonly seen even with active infection • Accompanied by a severe leukocytosis• Found in a small number if cells

Morphology: • Large aqua-staining rod • Esinophilic patches• May distort the cell border

• also be seen as a clear capsule

Hepatozoon canis

WBC Parasites

Ehrlichia ewingli and Ehrlichia canis• Bacterial parasite transmitted via ticks• More commonly seen in the south• Dogs can be asymptomatic or present with a fever and polyarthritis

• Accompanied by moderate leukopenia and severe thrombocytopenia

• Rarely seen on direct smear• Is a zoonotic dz

Ehrlichia spp.

Mporohology:• E. ewingli morula – found in neutrophils • E. canis – found in lymphocytes and monocytes• Both appear as medium well defined round-oval

inclusions within the cytoplasm that stain deep blue/purple

Ehrlichia ewingli

WBC Parasites

Anaplasma phagocytophilum• Tick-born bacterial parasite• Accompanied by a mild to moderate nonregenerative anemia and thrombocytopenia

• Not commonly seen even with a positive infection• Is a zoonotic disease

Anaplasma phagocytophilum

• Morphology:• Small deep blue/purple structures • Grouped individually or in grape-like clusters• Observed in cytoplasm of circulating neutrophils and

rarely in eosinophils

PLATELETS:THROMBOCYTES

Thrombocytes

• 1’st line of defense for the normal function of clotting• (aka: hemostasis)

• Formed and released from the bone marrow

• Lifespan in the blood is 5-10 days

• Observed/counted in counting area of the blood smear • Scan feathered edge of the smear to observe for clumps

Thrombocytes

Morphology• Lack a nucleus• Vary greatly in size, shape, and granularity• Often have fuzzy edges • Can have string-like projections arising from the body of the cell

• Stain pale lavender to dark purple

Thrombocytes

Normal morphology: Dog• Round, discoid, oval, elongated, or flat• Some appear granular

• Containing few purple/blue granules

surrounded by a pale blue matrix

Thrombocytes

Morphology: Cat• Morphologically similar to the dog• Spherical or elongated• Tendency to clump

• More variable in size• May be as large as the red blood cells

• considered normal

Thrombocyte Abnormalities

• 90% of bleeding disorders in dogs and cats results from abnormalities with either platelet numbers or platelet function

• Greyhounds tend to have a lower number of platelets overall

Thrombocyte Abnormalities

Activated platelets:• Spider/Thread-like projections

• Fibrin strands

• Smaller body

• Form platelet clumps

• Non-pathological finding

Thrombocyte Abnormalities

Clumping• Causes:

1. Sample collection (slow venipuncture)

2. Age of the sample (samples over 24 hours are prone to clumping)

3. Common in cats but is normal

• The feathered edge should be

scanned first to observe for this

abnormality, the clumps being

heavier tend to be pushed to the

edge of the smear

Thrombocytes

• Platelet clumping on feathered edge (10x magnification)

Thrombocyte Abnormalities

Mega platelets or megathrombocytes• Large platelets

• Can be an indication of an early production and release

• May be as large as the RBC’s

• Can be a normal in cats

Megathrombocytes

Platelet disorders

Quantitative abnormality• Thrombocytopenia: • Decreased number of platelets• Normal function

• Caused by:• Increased utilization of platelets • Increased destruction of platelets• Decreased production

Platelet disorders

Qualitative abnormalities:• Numbers are normal but the function is compromised• Hereditary function defect

• Ex: von wilebrans disease and hemophelia

• Very rare defect• Usually accompanied by and anemia and/or neutropenia

• Other causes: • Cancer, immune or infectious etiologies, NSAID’s

Platelet disorders

Thrombocytosis:• Increase in the number of platelets • Very rare, usually secondary to another problem

• Causes:• Iron deficiency’s anemia, certain inflammatory conditions,

severe trauma (fractures), certain drug therapies, neoplasia, certain gastrointestinal diseases

• Transient thrombocytopenia caused by excessive exercise or epinephrine injections

Questions?