Page 1380 - Small Animal Internal Medicine, 6th Edition

1352 PART XIII Hematology

BOX 82.4 TABLE 82.5
VetBooks.ir Classification and Causes of Nonregenerative Anemia in Distinguishing Features of Anemia of Chronic Disease
(ACD) and Iron Deficiency Anemia (IDA) in Dogs
Cats and Dogs
Anemia of chronic disease PARAMETER ACD IDA
Bone marrow disorders
• Bone marrow (or erythroid) aplasia-hypoplasia Serum iron concentration ↓ ↓↓
• Myelophthisis Total iron-binding capacity N N↑
• Myelodysplastic syndromes Percentage saturation ↓ ↓↓
• Myelofibrosis Bone marrow iron stores ↑ ↓
• Osteosclerosis, osteopetrosis
Anemia of renal disease Platelet count N, ↓, ↑ ↑, ↑↑
Acute blood loss or hemolysis (first 48-96 hours) Fecal occult blood N ±
Anemia of endocrine disorders Ferritin N ↓
• Hypoadrenocorticism
• Hypothyroidism ↓, Low; ↓↓, markedly low; ↑, high; ↑↑, markedly high; N, normal;
±, positive or negative.

encountered in which this form of anemia is acute—acute results in clinical signs of anemia and the patients are usually
blood loss (first 48-96 hours) and peracute hemolysis. In evaluated as a consequence of their primary disorder (e.g.,
these two cases, the bone marrow has not yet had time to cancer, infection). ACD develops secondary to a variety of
mount a regenerative reticulocyte response, and the patients chronic inflammatory, degenerative, or neoplastic condi-
have severe clinical signs. tions. Although the term anemia of chronic disease implies a
When evaluating dogs and cats with symptomatic nonre- chronic onset, it has been established that cats can develop
generative anemias of acute onset, the clinician should try to ACD in as little as 2 weeks. However, some of those cats were
answer the following questions: receiving fluid therapy that might have resulted in hemodilu-
tion (Ottenjan et al., 2006). In most cats with ACD, the PCV
• Has this patient had an acute blood loss or does it have values range from approximately 18% to 25%, whereas in
hemolytic anemia and has not yet been able to mount dogs they range from approximately 25% to 35%. Therefore
a regenerative response (i.e., <48-96 hours have elapsed ACD can usually be excluded in dogs with a PCV less than
since the event)? 20% and in cats with a PCV less than 17% to 18%. The RBC
• Does this patient have chronic anemia but is now symp- indices are normocytic and normochromic, and the CBC
tomatic because of intercurrent disease (e.g., heart failure, may also reflect the nature of the primary problem (e.g.,
sepsis)? leukocytosis, neutrophilia, monocytosis, hyperproteinemia
resulting from a polyclonal gammopathy). Some cats with
Most clinical and clinicopathologic abnormalities in cats ACD have microcytic hypochromic RBC indices, a condi-
and dogs with nonregenerative anemia have been discussed. tion that mimics IDA.
In general RBCs in dogs and cats with nonregenerative Sustained inflammatory or neoplastic processes cause
anemias are normocytic and normochromic; however, in iron to be sequestered within the bone marrow MPS, and it
cats with FeLV-related hypoproliferative anemias, RBCs are is therefore not available to the erythroid precursors for
usually macrocytic and normochromic. As noted, in dogs normal erythropoiesis. This unavailability of iron is mainly
and cats with IDA, the RBC indices are microcytic and mediated by hepcidin, lactoferrin, and other acute-phase
hypochromic. reactants released from leukocytes during inflammation. In
The clinical evaluation of a cat or dog with nonregenera- cats and dogs with ACD, the serum iron concentration and
tive anemia differs radically from that of a patient with a total iron-binding capacity (TIBC, or transferrin concentra-
regenerative form because the absence of regeneration tion) are usually decreased and the Hb saturation is low, but
reflects primary or secondary bone marrow abnormalities iron stores in the bone marrow are increased (Table 82.5).
(e.g., bone marrow disorder, ACD). Therefore, after extra- Although serum ferritin concentrations are the main feature
marrow causes have been ruled out by performing a physical that distinguishes ACD from IDA (i.e., high in ACD and low
examination and serum biochemical profile and urinalysis, in IDA) in humans, the results of ferritin assays in dogs and
a bone marrow aspiration or biopsy is typically indicated in cats with IDA and ACD are not as clear-cut. Therefore, to
these patients. differentiate ACD from IDA conclusively, evaluation of bone
marrow iron stores by Prussian blue staining is important.
Anemia of Chronic Disease After a diagnosis of ACD has been confirmed, every effort
ACD is the most common form of nonregenerative anemia should be made to identify the cause of the problem if it is
in cats and dogs, but because it is mild it almost never not already evident.