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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Chronic hemorrhage is rare in horses
  • May arise from the GI, urinary, or respiratory tract
  • Physiologic adaptations often obscure clinical signs until the PCV is <0.12 L/L
  • Regenerative responses usually compensate for losses until the rate of erythropoiesis is exceeded by the rate of blood loss, or if chronic blood loss occurs externally, when iron deficiency causes maturation arrest of marrow erythroid precursors
  • Chronic internal hemorrhage allows reutilization of some red blood cells, iron, and plasma protein
  • Chronic external hemorrhage often causes deficiencies of these blood constituents

Signalment!!navigator!!

No breed, sex, or age predilection.

Signs!!navigator!!

  • Overt signs (e.g. tachycardia, tachypnea, or weakness) may not occur until PCV <0.12 L/L
  • Pale mucous membranes, exercise intolerance, and marked increases in heart and respiratory rates may occur with stress
  • Other signs of an underlying disease process may be present

Causes and Risk Factors!!navigator!!

Depends on the primary disease process:

  • GI tract—severe parasitism, GI tract ulceration, neoplasia
  • Renal/urologic—hemorrhagic cystitis, urolithiasis, trauma, neoplasia, pyelonephritis
  • Respiratory—exercise-induced pulmonary hemorrhage, ethmoid hematoma, guttural pouch mycosis, fungal rhinitis, neoplasia
  • Miscellaneous—immune-mediated thrombocytopenia, coagulopathies

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

CBC/Biochemistry/Urinalysis!!navigator!!

  • Macrocytosis or increased mean cell volume may occur with regenerative anemia. Microcytic, hypochromic anemia with low serum iron, low marrow iron stores, and increased total iron-binding capacity may occur with chronic blood loss
  • Hypoproteinemia may reflect external blood loss although plasma total protein concentration may be normal due to compensation
  • Increased total and indirect bilirubinemia indicates internal blood loss
  • Chronic tissue hypoxia may cause increased serum hepatic enzyme activities and serum creatinine concentrations
  • Microscopic or gross hematuria may indicate a primary renal/urologic problem

Other Laboratory Tests!!navigator!!

See CBC/Biochemistry/Urinalysis.

Imaging!!navigator!!

  • Ultrasonography may identify NSAID-induced right dorsal colitis; intra-abdominal or intrathoracic masses
  • Upper respiratory tract radiography for sinus or ethmoidal masses

Other Diagnostic Procedures!!navigator!!

  • Bone marrow aspirate. If the myeloid to erythroid ratio is <0.5, the anemia is regenerative
  • Positive fecal occult blood indicates GI hemorrhage or blood swallowed
  • Positive fecal examination for parasitic ova supports a diagnosis of parasitism when accompanied by weight loss, diarrhea, or poor deworming history
  • Gastroscopy may reveal gastroduodenal ulceration or gastric squamous cell carcinoma
  • Cystoscopy may identify urethral, bladder, or ureteral hemorrhage
  • Upper airway endoscopy may demonstrate rhinitis, neoplasia, guttural pouch mycosis, ethmoid hematoma, or blood in the trachea
  • Erythrocytophagia and hemosiderophages may be identified in abdominal fluid, tracheal aspirate, or bronchoalveolar lavage fluid
  • Ultrasonography-guided biopsies of masses may help characterize the primary disease process

Treatment ⬆ ⬇

TREATMENT

  • Should be based on identification and elimination of the source of the underlying disease, which may necessitate inpatient care
  • Blood transfusion usually is unnecessary unless PCV is <0.10 L/L or there are signs of tissue hypoxia

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

If there is evidence of true iron deficiency, ferrous sulfate can be administered (2 mg/kg PO daily).

Contraindications/Possible Interactions!!navigator!!

Avoid parenteral iron dextran solutions; they can cause fatal reactions.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Response to treatment of the underlying disease should be assessed
  • Monitor response by weekly evaluation of PCV. Increase of PCV to the reference range should occur over 6–12 weeks
  • Serial bone marrow aspiration is rarely necessary
  • Client education should include recommendations regarding the underlying disease (e.g. parasite control)
  • Prognosis depends on identifying the underlying disease

Prevention/Avoidance!!navigator!!

  • Ensure correct dosing of NSAIDs
  • Parasite control program

Expected Course and Prognosis!!navigator!!

Dependent on the cause of chronic anemia.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

  • Anemia
  • Hemorrhage, acute

Age-Related Factors!!navigator!!

N/A

Zoonotic Potential!!navigator!!

N/A

Pregnancy/Fertility/Breeding!!navigator!!

Depends on the cause of chronic anemia.

Abbreviations!!navigator!!

  • GI = gastrointestinal
  • NSAID = nonsteroidal anti-inflammatory drug
  • PCV = packed cell volume

Suggested Reading ⬆ ⬇

Meindel MJ, Wilkerson MJ.Anemia. In: Sprayberry KA, Robinson NE, eds. Robinson's Current Therapy in Equine Medicine, 7e. St. Louis, MO: WB Saunders, 2015:471–475.

Author(s) ⬆

Author: Margaret C. Mudge

Consulting Editors: David Hodgson, Harold C. McKenzie, and Jennifer L. Hodgson

Acknowledgment: The author and editors acknowledge the prior contribution of Nicholas Malikides.