Anemia/Erythrocyte%20Disorders

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Anemia/Erythrocyte Disorders

• Laboratory Procedures

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Anemia

• Defined
• A condition of reduced oxygen carrying capacity
  of erythrocytes

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Erythrocyte disorders

• May be associated with
• Decreased production of RBCs
• Increased destruction of RBCs
• Inappropriate loss of RBCs

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Diagnosis

• A systemic, diagnostic approach to anemia is
  necessary and should include
• Good history
• Physical exam
• CBC
• Blood film/slide analysis

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Treatment

• Should be aimed at correcting the primary
  disorder and supporting the patient.
• IMPORTANT to establish whether the anemia is
  REGENERATIVE or NON-REGENERATIVE.
• Reticulocyte counts are used to evaluate if the
  anemia is regenerative or non-regenerative.
  WHY???
• Remember that regenerative anemias are usually
  the result of hemorrhage or hemolysis and
  non-regenerative anemias may involve the bone
  marrow.

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Treatment Continued

• Remember that regenerative anemias are usually
  the result of hemorrhage or hemolysis and
  non-regenerative anemias may involve the bone
  marrow.
• (Remember Myeloproliferative Disorders???)

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Regenerative v. non-regenerative

• Regenerative Anemia
• Increased reticulocytes, nRBCs, anisocytosis,
  polychromasia and Howell-Jolly bodies.
• Indicates the bone marrow has responded to a
  demand for RBCs by increasing production and
  releasing into circulation adequate numbers of
  immature RBCs (aka polychromatophils)

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Polychromatophils

• Bluish to reddish-blue cytoplasm
• Slightly larger than mature RBCs (why?)
• When stained with New Methylene Blue
  Reticulocytes

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Erythrocyte Life Span

• Stem Cell ? Rubriblast? Prorubricyte ? Rubricyte?
  Metarubricyte? Reticulocyte? RBC
• Metarubricyte- nucleated RBC released in severe
  anemia.

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ReticulocytesRemember these???

• Irregular net-like structures in
  polychromatophils when stained with New Methylene
  Blue. These structures are called reticulum.
• Reticulum is irregular clumps of ribosomal RNA
  and organelles like mitochondria.
• Most species only have one form of reticulocyte.
  Which species has two NORMALLY?

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Reticulocytes - continued

• Non-regenerative anemia
• Decreased production of erythrocytes caused by
  inadequate production of RBCs by the bone
  marrow.
• Canine reticulocytes when stained with New
  Methylene Blue are AGGREGATE only.
• Will appear as hyperchromatocytes and as
  macrocytes in comparison with normocytes.

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Feline Reticulocytes

• Punctate v. Aggregate
• The aggregate reticulocytes mature into the
  punctate form within 12 24 hours.
• Punctate reticulocytes circulate for 7 10 days
  before all RNA is lost.
• Reticulocyte counts of feline blood should only
  include the percentage of aggregate reticulocytes
  as punctate reticulocytes are not counted since
  they dont reflect the most recent bone marrow
  response.
• e.g. An anemic cat with only punctate
  reticulocytes is NOT actively regenerating RBCs
  at this time, but has shown some bone marrow
  regneration in the last 7 10 days.

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HemorRhage anemia

• Blood loss anemias are associated with acute,
  sub-acute and chronic hemorrhage.
• Hemorrhage Defined as the escape of blood from
  a ruptured vessel. May be external or internal.
• Acute Extremely sudden onset. Usually follows
  trauma or surgical procedures
• Sub-acute Recent or rather sudden onset. May
  take hours-days for clinical signs to appear.
• Chronic A continuous, constant loss of blood.
  Parasitism is most common cause of chronic
  anemias.

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Hemorrhage Anemia - Continued

• Most common cause of hemorrhage related anemia is
  trauma.
• Can also be caused by thrombocytopenia which is
  characterized by petechial hemorrhages on ear
  pinna(e), mucous membranes, and other non-haired
  areas like the abdomen.
• Treatment Includes steroids, plasma or whole
  blood transfusions, and avoidance of trauma.

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Iron-deficiency anemia

• Iron is important in the body because it is the
  main constituent of hemoglobin.
• Caused by chronic external blood loss.
• Note severe flea infestations, GI parasites,
  gastric ulcers and bleeding tumors can cause
  significant blood loss over time.
• The iron and hemoglobin lost with this external
  bleeding result in the formation of altered RBCs
  and decreased life span.
• Treatment includes correcting the cause of the
  blood loss and iron supplements.

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Hemolytic Anemia

• Defined The increased destruction of
  erythrocytes. (aka, hemolysis)
• Caused by immune components attaching directly or
  indirectly to the RBC membrane, altering its
  structure.
• The body, attempting to regain homeostasis,
  begins to remove these altered cells.
• In cats, the most common cause of hemolytic
  anemia is Mycoplasma haemofelis, a blood born
  parasite. Feline Leukemia can also stimulate an
  immunohemolytic anemia. Treatment is aimed at
  suppressing the immune system w/ steroid therapy.
• In dogs, the most common cause is an underlying
  inflammatory process.

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Blood-Borne Parasites

• Several commonly seen blood parasites can produce
  anemia through hemolysis.
• The parasite attaches to the erythrocyte
  membrane, causing an increased destruction of the
  cells.
• Animals having non-specific signs such as weight
  loss, anorexia, fever of unknown origin (FUO),
  hepatomegaly and splenomegaly should have blood
  films examined for the presence of blood
  parasites.

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Toxin-induced anemia/Heinz body anemia

• Drugs can be a source of anemia in small animals.
  
• Hemoglobin will denature and form Heinz Bodies.
• Cats are considered to be more susceptible to
  Heinz body formation due to the structure of
  their hemoglobin.
• One of the most common Heinz body anemias seen in
  the dog is onion toxicity.
• Acetaminophen toxicity can cause anemia in cats
  and dogs.

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Ehrilichiosis

• Ehrlichia is a rickettsial disease spread by the
  brown dog tick.
• First recognized in the US in 1963 and gained
  prominence because of the large losses among
  working military dogs stationed in Vietnam.
• Infection occurs when the organism is transported
  via the tick saliva during a blood meal.
• Infection is initially in WBCs.
• Can be transmitted from infected animal to
  non-infected animal.
• Infected circulating cells can infect other
  organs and may result in platelet consumption and
  erythrocyte destruction.

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Female Tick Laying Eggs
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Von Willebrands Disease

• Canine vWD is the most common inherited blood
  disorder.
• In healthy dogs, von Willebrands factor (vWF)
  promotes platelet clumping. Decreasing amounts
  of the factor causes a bleeding disorder.
• Has been identified in 54 breeds, with Doberman
  Pinschers, German Shepherds, and Labrador
  Retrievers being the most common.
• Dogs with this disorder should not be bred and
  special care must be taken at times of surgery to
  ensure hemostasis.