Page 1404 - Small Animal Internal Medicine, 6th Edition

1376 PART XIII Hematology

which the number of immature forms does not exceed the
number of mature neutrophils; most dogs and cats with BOX 85.2
VetBooks.ir a regenerative left shift have leukocytosis. A degenera- Causes of Neutrophilia in Cats and Dogs
tive left shift occurs when the number of immature forms
exceeds that of mature neutrophils; the number of the latter
may be normal, low, or high. Degenerative left shifts are Physiologic or Epinephrine-Induced Neutrophilia
• Fear (C)
usually suggestive of an aggressive disease; toxic neutrophil • Excitement (?)
changes (see earlier) are common in dogs and cats with • Exercise (?)
degenerative left shifts. Disorders commonly associated with • Seizures (D, C)
degenerative left shifts include pyothorax, septic peritoni- • Parturition (?)
tis, bacterial pneumonia, pyometra, prostatitis, and acute Stress- or Corticosteroid-Induced Neutrophilia
pyelonephritis. The term extreme neutrophilia refers to situ-
ations in which the neutrophil count is above 50,000/µL • Pain (?)
• Anesthesia (?)
9
(50 × 10 /L); it can be associated with a left shift or mature • Trauma (D, C)
neutrophilia. Diseases typically associated with extreme • Neoplasia (D, C)
leukocytosis include septic foci (e.g., pyometra), immune- • Hyperadrenocorticism (D)
mediated diseases, hepatozoonosis, mycobacteriosis, and • Metabolic disorders (?)
chronic myelogenous leukemia. A leukemoid reaction refers • Chronic disorders (D, C)
to a marked neutrophilia with a severe left shift, which
includes metamyelocytes and myelocytes. It indicates severe Inflammation or Increased Tissue Demand
inflammatory disease and may be difficult to distinguish • Infection (bacterial, viral, fungal, parasitic) (D, C)
from chronic granulocytic (myelogenous) leukemia (see • Tissue trauma and/or necrosis (D, C)
Chapter 80). • Immune-mediated disorders (D)
Although a high percentage of cats and dogs with neutro- • Neoplasia (D, C)
philia have underlying infectious disorders, neutrophilia is • Metabolic (uremia, diabetic ketoacidosis) (D, C)
• Burns (D, C)
not synonymous with infection. Rather, neutrophilia in cats • Neutrophil function abnormalities (D)
and dogs is commonly the result of inflammatory or neo- • Other (acute hemorrhage, hemolysis) (D, C)
plastic processes. Several disorders resulting in neutrophilia
are listed in Box 85.2. Note: Entries in boldface are common causes; entries in italics are
Of note, neutrophilia commonly results from endogenous relatively common causes; entries in regular typeface are
epinephrine release (physiologic neutrophilia). This neutro- uncommon causes.
philia, which is associated with the release of neutrophils C, Cat; D, dog; ?, poorly documented.
from the MNP, is transient (lasting 20-30 minutes after
endogenous release of catecholamines) and is commonly
associated with erythrocytosis and lymphocytosis, the latter abdominal ultrasonography (e.g., peritonitis, pancreatic or
primarily in cats. hepatic abscess), and the collection of blood, urine, fluid,
The endogenous release or exogenous administration of or tissue samples for cytology and bacterial and fungal cul-
corticosteroids results in stress- or corticosteroid-induced tures. As noted, autologous or allogeneic neutrophils labeled
neutrophilia, which are associated with decreased neu- with radionuclides (e.g., technetium-99m or indium-111)
trophil egress from the vasculature and increased bone can be injected intravenously and the septic focus or foci
marrow release of neutrophils from the storage pool. Other identified by gamma camera imaging, but this is rarely done;
hematologic changes typical of a stress leukogram include an inflammatory focus can also be detected by radiolabeled
lymphopenia, eosinopenia, and monocytosis; the latter is ciprofloxacin.
uncommon in cats. These abnormalities are commonly seen The treatment of dogs and cats with neutrophilia is aimed
in sick dogs and cats. Dogs with hypoadrenocorticism and at the primary cause. Empiric antibiotic therapy with a
inflammatory/infectious diseases typically lack the neutro- broad-spectrum bactericidal antibiotic (e.g., trimethoprim-
philic response of normal dogs; that is, they are sick but do sulfamethoxazole, enrofloxacin, cephalosporin, amoxicillin)
not have a stress leukogram. is an acceptable approach if a cause for the neutrophilia
Clinical signs in cats and dogs with neutrophilia are cannot be identified after exhaustive clinical and clinico-
usually secondary to the underlying disorder. Pyrexia may or pathologic evaluation or as the first line of treatment in a
may not be present. If the patient has persistent neutrophilia, fairly asymptomatic dog or cat.
the neutrophils display toxic changes (see p. 1371), or a
degenerative left shift is present, every effort should be made EOSINOPENIA
to identify a septic focus or an infectious agent promptly. The Eosinopenia is defined as an absolute decrease in the number
workup in these animals should include a thorough physical of circulating eosinophils. It is commonly seen as part of the
examination (e.g., abscess), thoracic and abdominal radi- stress leukogram or with exogenous corticosteroid adminis-
ography (e.g., pneumonia, pleural or abdominal effusion), tration and is usually of little clinical relevance.