section name header

Basics ⬇

Basics

Overview

  • Adults-caused by chronic external hemorrhage.
  • RBC produced by iron-limited erythropoiesis.
  • Importance-prompts clinician to look for chronic external blood loss.

Signalment

  • Fairly common in adult dogs.
  • Rare in adult cats.
  • Transient neonatal iron-deficiency anemia may occur at 5–10 weeks of age in kittens.

Signs

  • Signs of anemia (e.g., lethargy, weakness, and tachypnea) and underlying disease.
  • Intermittent melena with gastrointestinal blood loss.
  • Possible heavy bloodsucking parasite load.

Causes & Risk Factors

  • Chronic external blood loss.
  • Common causes-GI lymphoma, hookworms, GI neoplasia.
  • Less common-skin (e.g., severe flea infestation) and urinary tract.
  • Blood donor overuse.

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

  • Any cause of anemia, especially hemorrhage.
  • Microcytic anemia in portosystemic shunt disease may or may not be due to iron deficiency.
  • Anemia of inflammatory disease iron-limited erythropoiesis.

CBC/Biochemistry/Urinalysis

  • PCV usually but not always decreased, generally 10–40% in dogs.
  • Anemia either regenerative or non-regenerative.
  • Microcytosis-indicated by low normal or low MCV, accompanied by increased heterogeneity, detected by erythrocyte histogram widening or increased RDW.
  • RBC changes include microcytosis, hypochromia due to thin cell geometry, and keratocyte and schistocyte formation.
  • Newer erythrocyte indices MCVr and CHr, are sensitive for detecting iron-limited erythropoiesis; available on one hematology system.
  • Lab tests indicate iron-limited erythropoiesis, but may not differentiate true from functional iron deficiency. Clinical findings of inflammatory disease versus blood loss are required to differentiate cause of iron limited erythropoiesis. It is also possible that inflammatory disease and true iron deficiency may occur concurrently.
  • RBC morphologic changes-hypochromia (increased central pallor), oxidative lesions (e.g., keratocytes), fragmentation.
  • Decreased MCHC not sensitive or specific.
  • Thrombocytosis may occur.
  • Hypoproteinemia-consistent with blood loss.

Other Laboratory Tests

  • Hypoferremia (serum iron <70 µg/dL) and transferrin saturation <15% support the diagnosis.
  • Serum iron values may be normal during iron repletion, if blood loss is intermittent.
  • Fecal exam for hookworms.
  • Fecal examination for occult blood or melena.

Imaging

Imaging studies-GI disease that may account for blood loss.

Diagnostic Procedures

As indicated by underlying disease.

Treatment ⬆ ⬇

Treatment

Medications ⬆ ⬇

Medications

Drug(s)

Iron Supplementation

Parenteral Iron Supplementation

  • Initiate iron therapy with injectable iron.
  • Iron dextran-a slowly released form of injectable iron; one injection (10–20 mg/kg IM) followed by oral supplementation.

Oral Iron Supplementation

  • Animals with severe iron deficiency may have impaired intestinal iron absorption, making oral therapy of little value until partial iron repletion has occurred.
  • Follow injected iron with oral iron supplement for 1–2 months, or until resolved.
  • Kittens undergo spontaneous iron repletion beginning at 5–6 weeks of age.

Oral Iron Supplements

Contraindications/Possible Interactions

Oral iron is associated with unexplained death in kittens and should be avoided.

Follow-Up ⬆ ⬇

Follow-Up

Miscellaneous ⬆

Miscellaneous

Abbreviations

  • CHr = reticulocyte hemoglobin content
  • GI = gastrointestinal
  • MCHC = mean cell hemoglobin concentration
  • MCV = mean cell volume
  • MCVr = mean reticulocyte volume
  • PCV = packed cell volume
  • RBC = red blood cell
  • RDW = red cell distribution width

Author Glade Weiser

Consulting Editor Alan H. Rebar

Suggested Reading

Fry MM, Kirk CA. Reticulocyte indices in a canine model of nutritional iron deficiency. Vet Clin Pathol 2006, 35:172–181.

Radakovich LB, Santangelo KS, Olver CS. Reticulocyte hemoglobin content (CHr) does not differentiate true from functional iron deficiency in dogs. Vet Clin Pathol 2015, 44 (in press).

Steinberg JD, Olver CS. Hematologic and biochemical abnormalities indicating iron deficiency are associated with decreased reticulocyte hemoglobin content (CHr) and reticulocyte volume (MCVr) in dogs. Vet Clin Pathol 2005, 34:23–27.

Thrall MA. Regenerative anemias. In: Thrall MA, et al., Veterinary Hematology and Clinical Chemistry. 2nd ed. Ames, IA: Wiley-Blackwell, 2012, pp. 88–90.