Evaluation of Erythrocytes: Anemia and Regeneration Flashcards Preview

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Which of the following conditions distinguish intravascular from extravascular hemolysis? bilirubinuria bilirubinemia hemoglobinuria hemoglobinemia

hemoglobinemia hemoglobinuria


Name some causes of hemolytic anemias.

  • immune-mediated
  • hemoparasites
  • infectious agents
  • chemicals and plants
  • fragmentation
  • hypoosmolality
  • hypophosphatemia
  • hereditary RBC defects


What are some of the causes of immune-mediated erythrocyte destruction?

IMHA (mostly dogs) neonatal isoerythrolysis (mostly horses and cats) lupus erythematosus (dogs) incompatible blood transfusion penicillin and sulfonamides (horses) cephalosporins, levamisole, primicarb insecticide (dogs) propylthiouracil, and possible griseofulvin, albendazole (cats)


Describe the pathological mechanism of IMHA.

attachment of IgG or IgM causes fixation of complement to RBC membranes - Macrophages phagocytize them - forms spherocytes


How can you detect IMHA in a dog?

Coombs test - but be careful because false positives and negatives do occur


Name three erythrocyte parasites.

anaplasma (ruminants) mycoplasma (not in horses) babesia cytauxzoon felis (non regenerative) theileria (ruminants and horses)


Name some infectious agents that cause IMHA.

leptospira and clostridium (primarily ruminants and horses) FeLV (decreases RBC production mostly) EIA virus (acute stage of infection = "coggins") Sarcocystis species (cattle and sheep) trypanosoma (not imp. in US)


Name two chemicals/plants that can cause anemia. 


Name two causes of hypoosmolality.

hypotonic fluid administration - IV or oral

water intoxication 


Name two causes of hypophosphatemia.

decreased RBC ATP concentration

postparturient hemoglobinuria

ketoacidotic diabetes mellitus following insulin therapy (cats and dogs)

hepatic lipidosis (cats)

hyperalimentation (dogs and cats)


Miscellaneous hemolytic anemias

liver failure in horses

splenic torsion in dogs

selenium deficiency in cattle grazing on st. augustine grass

postparturient hemoglobinuria in cattle not associated with hypophospatemia


Causes of blood loss anemia


blood sucking parasites

coagulation disorders


GI ulcers

inflammatory bowel diseases


Distinguish between external and internal hemorrhage

External - erythrocytes, plasma, proteins and iron are lost to the world or a parasite; decreased PCV and TP

Internal - iron is conserved, some erythrocytes and plasma proteins may be reabsorbed from body cavities, slight hyperbilirubinemia may occur; decreased PCV and increased TP 


Causes of acute hemorrhage


recent surgery 

bleeding ulcers

bleeding tumors (esp. hemangiosarcoma)

severely marked decrease in platelets (thrombocytopenia usually less than 25k/microliter)

inherited or acquired coagulopathies 


Acute hemorrhage laboratory findings

usually does not cause appreciable thrombocytopenia

hematocrit is variable depending on time after hemorrhage

plasma protein concentration variable based on time after hemorrhage - initial probably unchanged, shifts start few hours post and continue for 2-3 days - decreased PCV and TP 12-24 hours after blood loss as a result of dilution by interstial fluid; TP will return to normal in about a week unless ongoing loss

in 3 days retics appear in blood, peak at 7-10 days


How can a chronic blood loss cause a non-regenerative anemia?

if severe iron deficiency develops


Lab findings of chronic blood loss

hypoproteinemia - if hemorrhage is ongoing

can be regenerative or non-regenerative

microcytic hypochromic if iron deficient

thrombocytosis (seen in 50% of cases)

fragmentation morphologies due to thin cells being produced


Describe the mechanism of the development of iron deficiency anemia. 

decreased bone marrow iron since iron used to maintain erythropoiesis 

iron stores absent - RBCs produced without iron

-> iron deficiency anemia characterized by microcytosis and hypochromasia 


Causes of iron deficiency anemia

dietary deficiency of iron (can be secondary to acidosis, excess vitamin C, or excess zinc)

copper deficiency (necessary for absorption of iron from GI and release of iron from stores in macrophages in the body; seen in ruminants)

chronic external blood loss - ie. bleeding ulcers, flea infestation


Name causes of a macrocytic anemia.

FeLV infection in cats

myeloproliferative disorders

folate deficiency



What are some causes of non-regenerative anemias?

  • Reduced erythropoiesis
    • chronic renal disease - decreased EPO, RBC lifespan
    • hormone deficiencies - ie. hypothyroid dogs
    • anemia of inflammatory dz
    • cytotoxic damage to bone marrow (chemo)
    • infectious agents
    • immune mediated
    • myelophthis
  • Defective erythropoiesis - disorders of heme/nucleic acid synthesis, abnormal erythroid maturation


What are the causes of anemia from chronic renal dz?

decreased erythropoietin production (=main mechanism)

supression of erythropoiesis by uremic toxins

decreased RBC lifespans - uremic toxins kill via extravascular hemolysis

hemorrhage - often have oral and GI ulcers due to uremia


Non regenerative anemias due to endocrine disorders produce what type of anemia? 

moderate normocytic normochromic

not associated with poikilocytosis


Describe the pathogenesis of anemia of chronic inflammatory dz. 

cytokines - inhibition of erythroid progenitor cells, insufficient EPO response, impaired iron absorption and release of iron stores from macrophages, increased iron sequestration in bone marrow, spleen and liver; shortened erythrocyte lifespan


What does an anemia of inflammatory disease look like?

mild to moderate non regenerative

slight microcytosis 


Name some disorders of nucleic acid synthesis and the anemias they cause.

folic acid deficiency - macrocytic anemia

cobalamin deficiency - macrocytic anemia in humans, normocytic anemia in dogs and cats with inherited defects in cobalamin absorption (giant schnauzers, border collies, beagles)


Pyridoxine (vitamin b6) deficiency causes what type of anemia?

microcytic anemia (due to disorder in heme synthesis)


Lab findings of chronic iron deficiency anemia

  • mild to severe anemia
  • slight to marked microcytosis
  • normal or decreased MCHC
  • slight to marked hypochromasia (dogs and ruminants)
  • low to high retic counts
  • poikilocytosis in severe animals
  • thrombocytosis
  • erythroid hyperplasia in marrow with little or no stainable iron (except this is normal in cats)
  • low serum iron concentration
  • normal or high serum TIBC
  • low saturation of transferrin with iron 
  • decreased serum ferritin


Why do erythroid precursors cluster around macrophages in the bone marrow and spleen?

They are obtaining their iron (required for hemoglobin synthesis) from these iron-storing cells as well as from circulating transferrin


Name two iron binding/transport proteins

transferrin - beta globulin, correlates with TIBC, transport

ferritin - primarily found in cells, few in plasma, correlates with total body iron stores, stain bone marrow with prussian blue to evaluate