VTNE Review: Blood Smear Evaluation

phagocytosis

the release of substances that modulate the immune system and the the production of antibodies

function of WBCs

neutrophils

• most abundant WBCs

• nucleus is irregular and elongated

• nucleus in horse neutrophils have heavily clumped, coarse chromatin

• bovine neutrophils have darker pink cytoplasm

• primary function is phagocytosis

• increased number usually indicate infection or inflammation

heterophil

in avians, reptiles, some fish, guinea pigs, rabbits, etc, this cell is functionally equivalent to a neutrophil

have distinct eosinophilic granules in their cytoplasm

band neutrophil

• nucleus is horseshoe shaped

eopsinophil

• contain a nucleus that is similar to that of neutrophils, but the chromatin is usually not as coarsely clumped

• canine:

  • granules vary in size, stain less intently than other species, dark red and round

• feline:

  • granules are small and rod shaped and numerous

• equine:

  • granules are large and round to oval, stain an intense orange color

• capable of phagocytosis but primary function is to modulate the immune system

• increased numbers are commonly seen in patients with allergic reactions and parasite infections

basophils

• nuclei are similar to monocytes

• granules in dogs are few in number and stain a purple to blue-black color

• equine and bovine granules are more numerous and tend to stain a blue-black color and may completely pack the cytoplasm

• feline granules are round and stain a light lavender color

• involved in the mediation of the immune system

• increased numbers are seen with a variety of inflammatory and infectious conditions

• not commonly seen on the blood smear

lymphocyte

• most abundant WBCs in ruminant patients

• slightly indented nuclei

• chromatin is coarsely clumped and the cytoplasm is light blue and scanty

• chromocenters which are areas of condensed chromatin should not be confused with nuclei

• normal bovine lymphocytes may contain nucleolar rings and are large and difficult to distinguish from monocytes or neoplastic lymphoid cells

• major function is the production of antibodies

• increased number often indicate a viral infection

monocytes

• largest of the WBCs

• nucleus is occasionally the shape of a kidney bean but it is often elongated, lobulated, amoeboid

• chromatin is more diffuse and cytoplasm is a blue gray color and it may contain vacuoles and small, pink granules

• major function is phagocytosis

• increased numbers are seen in a variety of chronic infections

Pelger-Huet anomaly

• congenital hereditary defect that is characterized by the hypo-segmentation of all the granulocyte nuclei

• believed to result from an autosomal-dominant trait and is most common in Australian shepherd dogs

nuclear hypersegmentation

• neutrophils with more than five lobes

• usually attributed to the aging of neutrophils either in vivo or in vitro

• seen in the blood smears of poodles with poodle macrocytosis

toxic change

• most common disease induced cytoplasmic changes in neutrophils

• associated with conditions such as inflammation, infection, and drug toxicity

• types include cytoplasmic basophilia, Dohle bodies, vacuoles or “foaminess”, and rarely, intensely stained primary granules referred to as toxic granulation

• thought to be caused by a decreased length of time of neutrophil maturation within the marrow

atypical lymphocytes

may have basophilic cytoplasm and cleaved nuclei and may show evidence of asynchronous maturation of the nucleus and cytoplasm

reactive lymphocytes

have increased basophilia and may have more abundant cytoplasm

sometimes have a larger and more convoluted nucleus

changes usually caused by antigenic stimulation secondary to vaccination or infection

also referred to as immunocytes

Birman cat neutrophil granulation anomaly

• contain fine eosinophilic to magenta granules

• inherited as an autosomal-recessive trait

• neutrophil function is normal and affected cats are healthy

Chediak-Higashi syndrome

• have large fused lysosomes within the cytoplasm and stain lightly pink or eosinophilic

• affected animals have a slight tendency to bleed, because their platelet function is abnormal

• most often reoprted in persian cats but can also occur in cattle, foxes, and other species

siderotic granules

• granules of hemosiderin may be present in the nuetrophils and monocytes of animals with hemolytic anemia

• appear similar to Dohle bodies but can be differentiated with the use of Prussian blue stain

smudge cells

• sometimes referred to as basket cells

• degenerative leukocytes that have ruptured

• large numbers are associated with leukemia

karyolysis

degenerative change to the nucleus that is characterized by the dissolution of the nuclear membrane

usually affects neutrophils and is associated with the presence of septic exudates

karyorrhexis

refers to the fragmentation of the nucleus after cell death

pyknosis

refers to the condensing of the nucleus as the cell dies

rouleaux

• involves the grouping of erythrocytes in stacks

• increased formation is seen with increased fibrinogen or globulin concentrations

• accompanied by an increase in the erythrocyte sedimentation rate

• seen in healthy horses and may also be present from healthy cats and pigs

autoagglutination

• occurs in immune mediated disorders in which antibody coats the erythrocyte, resulting in bridging and clumping of RBCs

anisocytosis

• variation in the size of RBCs

• may indicate the presence of microcytes and/or macrocytes

• common finding in normal bovine blood

polychromasia

• refers to erythrocytes that exhibit a bluish tint when stained with Romanowsky-type stain

• blue tint is a result of the presence of organelles that remain within the cytoplasm (young cells)

• seen in high numbers during regenerative anemia

hypochromasia

• decreased staining intensity that is caused by an insufficient amount of hemoglobin within the cell

• iron deficiency is the most common cause

• will always have microcytosis which is determined by a decreased MCV

hyperchromatophilic

• refers to cells that appear to be more darkly stained than normal

• gives the appearance that the cells are oversaturated with hemoglobin

• usually microcytes or spherocytes

poikilocytes

• abnormally shaped erythrocytes

schistocytes

• RBC fragments, usually formed as a result of the shearing of the RBC via intravascular trauma

• may be observed with DIC when erythrocytes are broken by fibrin strands, with vascular neoplasms and with iron deficiency

acanthocytes

• also called spur cells

• irregular, spiculated RBCs with a few unevenly distributed surface projections of variable length and diameter

• seen in patients with altered lipid metabolism

• presence in middle aged to old large breed dogs with concurrent regenerative anemia is suggestive of hemangiosarcoma

echinocytes

• also called burr cells

• spiculated cells with numerous short, evenly spaced, blunt to sharp surface projections of uniform size and shape

• common term for abnormality is crenation

• can be seen in:

  • renal disease and lymphosarcoma in dogs

  • after exercise in horses

  • samples from healthy pigs

  • after rattlesnake, coral snake, water moccasin, and asp viper envenomation in dogs

drepanocytes

• also called sickle cells

• observed in the blood of normal deer and angora goats

• thought to be an in vitro phenomenon that is caused by high oxygen tension

keratocytes

• referred to as helmet cells, blister cells, or bite cells

• has been associated with hemangiosarcoma, neoplasia, glomerulonephritis, and various hepatic diseases

• cell may appear to contain a vacuole

• believed to form from intravascular trauma that involves the bisection of the cell by fibrin strands

• have also been demonstrated in blood from patients with anemia, liver disorders, and myelodysplastic syndrome

spherocytes

• darkly staining RBCs with reduced or no central pallor

• not easily detected in species other than dogs

• have a reduced amount of membrane surface area as a result of partial phagocytosis

• suggest the immune mediated destruction of RBCs, resulting in hemolytic anemia

• also may be seen after transfusion with mismatched or improperly stored blood, after snake envenomation, RBC parasites, and zinc toxicity

leptocytes

• characterized by an increased membrane surface area relative to cell volume

• target cells have a central area of pigment surrounded by a clear area and then a dense ring of peripheral cytoplasm

• may also appear as folded cells

• barr cells

target cell

barr cell

elliptocytes

• erythrocytes from camelid species and nonmammals are normally oval or elliptical in shape

• in other species, these cells are associated with lymphoblastic leukemia, hepatic lipidosis, portosystemic shunts, and glomerulonephritis

eccentrocytes

• described in patients with DKA or neoplasia, with Babesia canis infections, and after the ingestion of oxidants such as garlic, onions, and acetaminophen

• appear to have their hemoglobin primarily pushed to one side

dacryocytes

• tear drop shaped cells that are seen with myelofibrosis and certain other myeloproliferative diseases

• also identified in blood from llamas and alpacas that are iron deficient

basophilic stippling

• presence of small, dark blue bodies within the erythrocyte

• observed in Wright stained cells and represents residual RNA

• common in immature RBCs of ruminants and occasionally in cats during a response to anemia

• also characteristic of lead poisoning

Howell Jolly bodies

• basophilic nuclear remnants that are seen in young erythrocytes during the response to anemia

• increased numbers may be seen after the removal of the spleen or with splenic disorders

Heinz bodies

• round structures that represent denatured hemoglobin and that are caused by certain oxidant drugs or chemicals

• denatured hemoglobin becomes attached to the cell membrane and appears as a pale area with Wrights stain

• normal cats have Heinz bodies in as many as 5% of their RBCs

• often increased in concentration with diseases such as lymphosarcoma, hyperthyroidism, and diabetes mellitus in cats

nucleated erythrocytes

• represent early release of immature cells during anemia

aggregate and punctate (cats) reticulocytes