Page 1400 - Small Animal Internal Medicine, 6th Edition

1372 PART XIII Hematology

MATURATION MARGINAL
VetBooks.ir PROLIFERATIVE STORAGE CIRCULATING

BONE MARROW VASCULAR
COMPARTMENT COMPARTMENT
FIG 85.2
Theoretical neutrophil compartments in bone marrow and
blood.

A basic review of neutrophil physiology follows. Three
theoretical physiologic neutrophil compartments exist in the
FIG 85.1 bone marrow (Fig. 85.2). The proliferative compartment is
Left shift and toxic changes in a dog with an intraabdominal composed of dividing cells (myeloblasts, progranulocytes,
abscess (Diff-Quik stain; ×1000). and myelocytes); myeloblasts take approximately 48 to 60
hours to mature into metamyelocytes. The maturation com-
and Döhle bodies (small, bluish cytoplasmic inclusions partment consists of metamyelocytes and band neutrophils;
that consist of aggregates of endoplasmic reticulum). This the transit time through this compartment is 46 to 70 hours.
change occurs in the bone marrow and indicates that the The storage compartment is composed of mature neutro-
neutrophils are “losing the battle” against the offending phils; the transit time in this compartment is approximately
agent. 50 hours, and it contains an estimated 5-day supply of neu-
2. Giant neutrophils, bands, and metamyelocytes are large trophils. Mature neutrophils leave the bone marrow by a
polyploidal cells that may result from skipped cell divi- random process that involves changes in cell deformability
sion; they represent yet another manifestation of systemic and adhesiveness.
inflammation and are more common in cats than dogs. Two neutrophil pools are present in the vascular com-
partment (see Fig. 85.2). The marginal neutrophil pool
Other neutrophil morphologic abnormalities recognized (MNP) consists of neutrophils that are adhered to the
during a careful examination of blood smears include the vascular endothelium (and are thus not counted during a
Pelger-Huët anomaly (cats and dogs) and Chédiak-Higashi CBC). The circulating neutrophil pool (CNP) consists of the
syndrome (cats). The Pelger-Huët anomaly occurs when the neutrophils circulating in the blood (i.e., the cells counted
nucleus of polymorphonuclear leukocytes fails to divide, but during a differential WBC count). The total blood neutro-
the nuclear chromatin and cytoplasm maturation is com- phil pool is composed of the MNP plus the CNP. In dogs
plete (i.e., the nucleus has a band-like appearance, with the CNP is approximately equal in size to that of the MNP.
mature clumped chromatin). Cats and dogs with this However, in cats the MNP is approximately two to three
anomaly typically have profound “left shifts” in the absence times the size of the CNP. The neutrophil has an average
of clinical signs. On careful examination of the smear, blood transit time of approximately 6 to 8 hours in dogs and
however, the cells in the left shift are mature cells with 10 to 12 hours in cats, with all blood neutrophils replaced
nuclear hyposegmentation and not immature neutrophils. every 2 to 2.5 days. Once the neutrophils leave the blood
This anomaly may be acquired or inherited (autosomal dom- vessel (by diapedesis), they normally do not return to the
inant) and is usually considered of minimal clinical rele- circulation and are lost in the lungs, gut, other tissues, urine,
vance. We have seen it primarily in Australian Cattle dogs or saliva.
and in dogs undergoing chemotherapy.
Chédiak-Higashi syndrome, a lethal autosomal recessive
condition of Persian cats with smoke-colored haircoats and LEUKOCYTE CHANGES IN DISEASE
yellow eyes, is characterized by enlarged neutrophilic and
eosinophilic granules in association with partial albinism, Because the lower limit for the reference range for basophil
photophobia, increased susceptibility to infections, bleeding and monocyte counts is 0, basopenia and monocytopenia are
tendencies, and abnormal melanocytes. not discussed.
Nuclear hypersegmentation (i.e., four or more distinct
nuclear lobes) may result from a prolonged neutrophil transit NEUTROPENIA
time (old neutrophils). It occurs in dogs with hyperadreno- Neutropenia is defined as an absolute decrease in the number
corticism, cats and dogs receiving corticosteroid therapy, of circulating neutrophils. It can result from decreased (or
and cats and dogs with chronic inflammatory disorders. impaired) cell production within the bone marrow or from