ANEMIA in Animals

Anemia is an absolute decrease in RBC numbers, hemoglobin concentration, or PCV.

  • Signs include pale mucous membranes, increased heart rate, and hypotension. Diagnosis can be made by CBC, but may be refined by additional tests. Treatment can be symptomatic, but often requires addressing the underlying cause. Anemia is defined as an absolute decrease in the red cell mass as measured by RBC count, hemoglobin concentration, and/or PCV.
  • It can develop from loss, destruction, or lack of production of rbcs. Anemia is classified as regenerative or nonregenerative
  • With regenerative anemia, the bone marrow responds appropriately to the decreased red cell mass by increasing RBC production and releasing reticulocytes. With nonregenerative anemia, the bone marrow responds inadequately to the increased need for rbcs.
  • Anemia caused by hemorrhage or hemolysis is typically regenerative. Anemia caused by decreased erythropoietin or an abnormality in the bone marrow is nonregenerative

Clinical Findings:

Clinical signs in anemic animals depend on the degree of anemia, the duration (acute or chronic), and the underlying cause. Acute anemia can result in shock and even death if more than a third of the blood volume is lost rapidly and not replaced. In acute blood loss, the animal usually presents with one or more of the following:

●         tachycardia

●         pale mucous membranes

●         bounding or weak peripheral pulses

●         hypotension

The cause of the blood loss may be overt, e.g., trauma. If no evidence of external bleeding is found, a source of internal or occult blood loss must be sought, e.g., a ruptured splenic tumor, other neoplasia, coagulopathy, GI ulceration, or parasites. If hemolysis is present, the animal may be icteric.

Animals with chronic anemia have had time to accommodate, and their clinical presentation is usually more indolent with vague signs such as:

●         lethargy

●         weakness

●         anorexia

These animals may have similar physical examination findings such as pale mucous membranes and weak peripheral pulses. The lack of expected clinical signs may alert the clinician to the time frame involved. Splenomegaly, abdominal distention, and/or heart murmur may be present,depending on the underlying cause of anemia.


Clinical Evaluation

A complete history is an important part of the evaluation of an anemic animal. Questions might include duration of clinical signs, history of exposure to toxins (e.g., rodenticides, heavy metals, toxic plants), drug treatments, vaccinations, travel history, and any prior illnesses.

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Serologic Testing

  • A CBC, including a platelet and a reticulocyte count, will provide information on the severity of anemia and degree of bone marrow response and also allow for evaluation of other cell lines.
  • A blood smear should be evaluated for abnormalities in RBC morphology or size and for RBC parasites.
  • The RBC indices (measures of size and hemoglobin concentration) are calculated by automated cell counters calibrated for the species in question.
  • RBC size is expressed by the mean corpuscular volume (MCV) in femtoliters and can reflect the degree of regeneration. Macrocytosis (an increase in the MCV) usually correlates with a regenerative anemia
  • Macrocytosis can be a heritable condition in Poodles without anemia and may be seen in anemic cats infected with feline leukemia virus. Microcytosis (a decrease in the MCV) is the hallmark of iron-deficiency anemia and can also be heritable in Akitas.
  • Anemia in animal

Key Points

  • Anemia can be defined as regenerative or nonregenerative and is based on classic findings noted on a CBC or blood smear evaluation. Regenerative vs. Nonregenerative anemia can help narrow a list of differential diagnoses.
  • Plasma protein can be useful in classifying the underlying cause of anemia.
  • Clinical signs depend on the severity and duration (acute vs. Chronic) of the anemia.
  • Bone marrow evaluation may be necessary for further characterization of nondegeneracy

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