Page 1372 - Small Animal Internal Medicine, 6th Edition

1344 PART XIII Hematology

BOX 82.3
VetBooks.ir Pathogenetic Classification of Anemias

Regenerative
Blood loss (after 48-96 hours)
Hemolysis

Semiregenerative
IDA

Nonregenerative
ACD
ARD
Bone marrow disorder
Blood loss/hemolysis (first 48-96 hours)
Endocrine anemia
FIG 82.2
Strongly regenerative anemia in a dog depicting ACD, Anemia of chronic disease; ARD, anemia of renal disease;
anisocytosis, polychromasia, and nucleated RBCs, including IDA, iron deficiency anemia.
a large immature rubricyte (middle) (×1000).
the diagnosis is still uncertain after evaluating the blood
smear. Some of the abnormalities detected during a careful
examination of the blood smear and their clinical implica-
tions are summarized in Table 82.2. This evaluation should
be conducted under an oil immersion lens in a monolayer
field in which the erythrocytes are in a single layer and 50%
of the cells are touching.
A CBC and reticulocyte count in an anemic patient
provide more absolute data by which to assess the degree of
regeneration. However, the information presented here must
be used cautiously because the number of reticulocytes
should increase proportionally to the decrease in the HCT.
For example, a reticulocyte count of 120,000/µL (or ≈4%)
represents an appropriate response for a dog with an HCT
of 30% but not for one with an HCT of 10%.
With the advent of automated analyzers that provide
reticulocyte counts, it has become apparent that up to 10%
of dogs with normal HCT have a high reticulocyte count. We
now know that excitement causes the release of reticulocytes
FIG 82.3
RBC dot plot of a dog with strongly regenerative anemia from the spleen into systemic circulation; hence, an excited
(reticulocyte count, 360,000/µL) due to immune mediated dog will likely have a higher reticulocyte count than a calm
hemolysis. Note the large reticulocyte cloud in purple one. Approximately half of the dogs with a normal HCT and
(RETICS). Fig. 82.1, A, depicts a normal canine RBC dot high reticulocyte count have catecholamine-related splenic
plot for comparison. PLT, Platelets. release of reticulocytes. The other half are the most impor-
tant ones: they are usually dogs with early immune-mediated
appropriately to the anemia (i.e., whether the anemia is hemolysis or with hemangiosarcoma (HSA); they are not yet
regenerative or not; see Figs. 82.2 and 82.3). Several pieces sufficiently anemic, but they are regenerating. Therefore a
of information can be acquired during the examination of blood smear should always be evaluated in a dog with reticu-
a good-quality, properly stained blood smear, including locytosis, regardless of the HCT.
the RBC size and morphology, approximate numbers and Overall, normal dogs and cats with a normal HCT have less
morphology of white blood cells and platelets, and pres- than 100,000 reticulocytes/µL and 50,000 reticulocytes/µL,
ence of autoagglutination, nucleated RBCs, hypochromasia respectively. Most dogs have between 10,000 and 60,000/µL.
(IDA), polychromasia (indicative of regeneration), and RBC As noted, when evaluating dot plots from a LaserCyte or Pro-
parasites. Ideally, the clinician or technician should always CyteDx (IDEXX), the presence of a large reticulocyte cloud
perform this cursory evaluation of the blood smear; a blood is almost always indicative of regeneration (see Fig. 82.3);
sample should be submitted to a diagnostic laboratory for however, given that dogs with IDA frequently have reticu-
further analysis and evaluation by a clinical pathologist if locytosis, the MCV and MCHC should also be evaluated.