Anemia/Erythrocyte
Disorders
Laboratory Procedures
Anemia
• Defined:
• A condition of reduced oxygen
carrying capacity of erythrocytes
Erythrocyte
disorders
• May be associated with:
• Decreased production of RBC’s
• Increased destruction of RBC’s
• Inappropriate loss of RBC’s
Diagnosis
• A systemic, diagnostic approach to anemia is
necessary and should include:
•
•
•
•
Good history
Physical exam
CBC
Blood film/slide analysis
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.
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???)
Regenerative v. non-regenerative
• Regenerative Anemia:
• Increased reticulocytes, nRBC’s, anisocytosis,
polychromasia and Howell-Jolly bodies.
• Indicates the bone marrow has responded to a demand
for RBC’s by increasing production and releasing into
circulation adequate numbers of immature RBC’s (aka
polychromatophils)
Polychromatophils
• Bluish to reddish-blue cytoplasm
• Slightly larger than mature RBC’s (why?)
• When stained with New Methylene Blue = Reticulocytes
Erythrocyte Life
Span
• Stem Cell → Rubriblast→ Prorubricyte → Rubricyte→
Metarubricyte→ Reticulocyte→ RBC
• Metarubricyte- nucleated RBC released in severe
anemia.
Reticulocytes
Remember 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?
Reticulocytes - continued
• Non-regenerative anemia
• Decreased production of erythrocytes caused by
inadequate production of RBC’s 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.
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 don’t reflect the most recent bone marrow response.
•
e.g. An anemic cat with only punctate reticulocytes is NOT actively
regenerating RBC’s at this time, but has shown some bone marrow regneration
in the last 7 – 10 days.
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.
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.
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 RBC’s and decreased life
span.
• Treatment includes correcting the cause of the blood loss
and iron supplements.
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.
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.
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.
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 WBC’s.
• 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.
Female Tick Laying
Eggs
Von Willebrand’s
Disease
• Canine vWD is the most common inherited blood disorder.
• In healthy dogs, von Willebrand’s 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.