Clinical presentation of dogs (or cats) withanemia varies with the severity and durationof the anemia, and with the underlyingdisease. There may be few historical findingsrelated to anemia and often it is an incidentalfinding when labwork is performed.Listlessness (which may also be described aslethargy, weakness or reduced exercisetolerance) and inappetence, although commoncomplaints in dogs with anemia, are non-specific findings. Other historical complaintsseen in patients with anemia can includecollapse, syncope, and evidence of hemorrhageor hemolysis (icterus or pigmenturia). Youmay need to ask the client more specificquestions to reveal this background.

A careful physical examination can providehelpful information regarding anemia.Physical examination findings in dogs withanemia depend on the underlying diseaseprocess and severity of anemia. Findings mayinclude mucous membrane pallor, tachypnea,tachycardia, a soft systolic heart murmur (notlouder than grade III/IV), and pulse changes(hyperkinetic femoral pulses). Animals withhemorrhagic shock have the above findingsexcept that pulses will be weak, extremitiescool, and a heart murmur may or may not bepresent. Other findings associated with specifictypes of anemia may include icterus(hemolysis), fever (infectious, immune-mediated, or neoplastic disease), hemorrhages(hemostatic problem, trauma),hepatosplenomegaly (immune-mediateddisease, neoplasia, spenic torsion, infection),and endocrine alopecia (hypothyroidism).

CANINE ANEMIAS

May • 2000

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LABORATORY CLASSIFICATION OF ANEMIA

Classification of anemia is an importantstep in determining the cause, best approachto treatment, and prognosis.

1. Severity based on hematocrit(packed cell volume, PCV) – an arbitrary classification

Severity PCVMild 30 - 37%Moderate 20 - 30%Severe 10 - 20%Critical < 10%

Mild, non-regenerative anemias areoften caused by chronic disease and maynot be worth pursuing. Anemia of chronicdisease in dogs typically does not producea hematocrit <20%, so the magnitude ofanemia can be very helpful in determiningcause.

2. Regenerative versus non-regenerative There are many laboratory indicators

that an anemia may be regenerative,including macrocytosis and perhapshypochromasia (decreased MCHC),increased anisocytosis, and presence ofHowell Jolly bodies, normoblastemia,polychromasia, and reticulocytosis.Antech Diagnostics grades polychromasiaon the following scale:

Grade % Polychromatic RBCs1+ 2 - 5%2+ 6 - 10%3+ 11 - 15%4+ > 15%

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CANINE ANEMIAS (CONT’D.)

The gold standard for evaluatingwhether anemia is regenerative ornon-regenerative is the presence orabsence and degree of reticulo-cytosis. A corrected reticulocytepercentage (%) or absolute reticulo-cyte number is required to correctthe raw reticulocyte % for the effectof anemia.

WHY IS THIS IMPORTANT?As an example, consider a

reticulocyte % of 5. Five % reticu-locytes in a dog with a PCV of 20% istwice as many reticulocytes as 5%reticulocytes in a dog with a PCV of10%. There are 2 ways to correct thereticuloycte % for the degree ofanemia, as follows:

a. Corrected retic. % = reticulocyte % x (patient PCV%)

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A corrected reticulocyte % of< 1% indicates a non-regenerativeanemia. The higher the correctedvalue, the stronger the regener-ative response.

b. Absolute reticulocyte number =reticulocyte % x RBC count

An absolute reticulocytecount of < 60,000 cells/µlindicates a non-regenerativeanemia. The higher thereticulocyte count, the strongerthe regenerative response.

These 2 methods do exactly thesame thing (correct for the effect ofanemia) and give the sameinterpretation.

The reticulocyte production index,which is a modification of thecorrected reticulocyte %, is not anessential value and its validity hasbeen questioned.

RULE OUTS FOR REGENERATIVEANEMIAS:1. Hemorrhage

a. Peracute (over minutes tohours) and acute (over hoursto days) blood loss willinitially be non-regenerative.

Development of a fullregenerative response takes 5-7days after the onset of anemia.

b. Chronic blood loss anemia maybecome non-regenerative andmicrocytic due to irondeficiency.

c. Hemorrhage may be due to acoagulopathy or to some localdisease (eg, tumor, ulcer,trauma).

d. Hemorrhage is often occult,such that the lack of visiblebleeding cannot be used toexclude it as a cause foranemia.

2. Hemolysis (decreased RBClifespan)

a. May occur intra- or extra-vascularly, and may be due tointrinsic red cell abnormalities(such as pyruvate kinase orphosphofructokinase deficien-cies) or disorders outside thered cell (AIHA, zinc or oniontoxicoses, hypophosphatemia,snake envenomation, and DIC).

b. Acute hemolytic anemia maybe non-regenerative. Develop-ment of a full regenerativeresponse takes 5-7 days afterthe onset of anemia.

c. Immune-mediated hemolyticanemia also can be non-regenerative, if it involvesattack of bone marrowprecursors.

d. Patient signalment, or clientreport of pigmenturia, orangestool, or toxin exposure (onion,zinc) can increase the clinicalindex of suspicion for hemo-lysis. Laboratory abnormalitiesthat support hemolysis as acause of anemia include:presence of markedregenerative anemia alongwith a normal total protein,hyperbilirubinemia, abnormalbilirubinuria, hemoglobinemia,hemoglobinuria, red cellautoagglutination, presence ofHeinz bodies or numerousspherocytes.

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WHEN IS BONE MARROWEVALUATION NECESSARY?

Indications for bone marrowevaluation include non-regenerativeanemias without apparent cause,presence of pancytopenia or anemiaand neutropenia, and reports of“blasts” or atypical cells onperipheral blood smear review.

RULE OUTS FOR NON-REGENERATIVE ANEMIAS:1. Anemia of chronic disease2. Renal failure3. Endocrinopathies

a. Addison’s diseaseb. Hypothyroidism

4. AIHA with bone marrowinvolvement (maturation arrestor red cell hypoplasia).

5. Bone marrow disease such asmyelodysplasia, hematopoieticneoplasia, myelophthisis(crowding out of marrow bycancer cells), aplastic anemia(phenylbutazone, estrogen,phenobarbital, radiation),ehrlichiosis, and systemicmycoses.

6. Nutritionala. Iron deficiencyb. Folic acid deficiency (seen

occasionally in severe intestinal disease)

c. Protein-calorie malnutrition7. Early hemorrhage or hemolysis

ACTH PREPARATIONS

We currently recommend usingthe synthetic ACTH productcosyntropin (Cortrosyn®; OrganonPharmaceutical) for ACTH responsetesting in dogs and cats. To reducereagent cost, consider using themini-dose regime: measure serumcortisol before and 1 hour after IVadministration of 5 µgm/kgcosyntropin. The reconstituted vialcan be stored refrigerated for up to2 months without loss of bioactivity.