Veterinary Hematology Overview
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Questions and Answers

Which species has the highest mean corpuscular volume (MCV) values indicating the largest red blood cells (RBCs)?

  • Sheep
  • Goats
  • Dogs (correct)
  • Llamas

    • What do hypochromic red blood cells indicate in terms of hemoglobin concentration?

  • Increased cholesterol levels
  • Normal hemoglobin levels
  • Decreased hemoglobin concentration (correct)
  • High iron concentration

    • Heinz bodies are associated with which type of damage to red blood cells?

  • Physical trauma to the RBCs
  • Viral infections
  • Nutritional deficiencies
  • Oxidant damage (correct)

    • Acanthocytes are commonly observed in which specific conditions?

    <p>Hepatic lipidosis in cats and hemangiosarcoma in dogs</p> Signup and view all the answers

    What is the cause of basophilic stippling in red blood cells?

    <p>Aggregation of ribosomes into small granules</p> Signup and view all the answers

    Which of the following is true regarding the classification of anemia?

    <p>MCH and MCHC are used to classify anemia</p> Signup and view all the answers

    What condition typically results in pale red blood cells with a decreased concentration of hemoglobin?

    <p>Iron deficiency</p> Signup and view all the answers

    What appearance do Heinz bodies take when stained with methylene blue?

    <p>Blue and pale</p> Signup and view all the answers

    What is the primary concern when interpreting plasma protein concentration in the presence of hyperlipemia?

    <p>It can falsely increase the plasma protein concentration by 2 g/dL.</p> Signup and view all the answers

    Which method can be used to determine total leukocyte concentration?

    <p>Unopette dilution or particle counting instruments.</p> Signup and view all the answers

    Which of the following is true regarding reticulocyte regeneration in dogs?

    <p>Regeneration takes at least 3 days before reticulocytes appear in circulation.</p> Signup and view all the answers

    How does hemoglobin concentration relate to packed cell volume (PCV) in most species?

    <p>It is approximately one-third of the PCV.</p> Signup and view all the answers

    What does an increased mean cell volume (MCV) indicate about RBCs?

    <p>They indicate increased red cell turnover.</p> Signup and view all the answers

    Which term describes the variation in red blood cell size?

    <p>Anisocytosis.</p> Signup and view all the answers

    Which type of red blood cell abnormality is caused by intravascular trauma?

    <p>Schistocytes.</p> Signup and view all the answers

    Which characterization best describes the red blood cells of Akita and Shiba Inu dogs?

    <p>They normally exhibit microcytic RBCs.</p> Signup and view all the answers

    What are codocytes primarily associated with in animals?

    <p>Increased serum cholesterol concentrations</p> Signup and view all the answers

    What characteristic feature distinguishes stomatocytes from other red blood cells?

    <p>Presence of a clear mouth-like area in the center</p> Signup and view all the answers

    What does polychromasia indicate in a blood sample?

    <p>Young erythrocytes with a reticulocyte response</p> Signup and view all the answers

    Which type of anemia is characterized by red blood cells of normal volume?

    <p>Normocytic anemia</p> Signup and view all the answers

    Why might band cells be present in peripheral blood, albeit in small numbers?

    <p>As a result of increased red blood cell production</p> Signup and view all the answers

    What is a key identifying feature of metamyelocytes?

    <p>Bean-shaped nucleus not typically found in blood</p> Signup and view all the answers

    What would suggest an increased mean corpuscular volume (MCV) in red blood cells?

    <p>Macrocytic anemia</p> Signup and view all the answers

    What does the presence of rouleaux formation in blood indicate?

    <p>Inflammation and infection</p> Signup and view all the answers

    Which statement accurately describes metarubricytes?

    <p>They are smaller than rubricytes and still contain a nucleus.</p> Signup and view all the answers

    What characterizes polychromatophilic erythrocytes?

    <p>They contain nuclear remnants and may appear blue-pink.</p> Signup and view all the answers

    Which of the following best describes acute inflammatory changes in neutrophils?

    <p>They are accompanied by a left shift within a few hours.</p> Signup and view all the answers

    What is true about granulocyte (myeloid) cells?

    <p>They are derived from stem cells.</p> Signup and view all the answers

    Which of the following is accurate regarding the maturation sequence of megakaryocytes?

    <p>The sequence starts with megakaryoblasts and ends with mature megakaryocytes.</p> Signup and view all the answers

    What defines toxic neutrophil changes in the context of acute inflammation?

    <p>They indicate a severe infection or inflammation.</p> Signup and view all the answers

    How do rubricytes differ from their precursor cells?

    <p>They have less coarse chromatin compared to prorubricytes.</p> Signup and view all the answers

    Which anatomical site is considered optimal for bone marrow aspiration in small dogs and cats?

    <p>Proximal femur</p> Signup and view all the answers

    What is the approximate myeloid-erythroid (M:E) ratio in normal conditions?

    <p>0.5:1 to 3:1</p> Signup and view all the answers

    Which cell type should be present at least 5 to 10 per slide for a proper hematological evaluation?

    <p>Megakaryocytes</p> Signup and view all the answers

    What is a potential reason for the increased number of macrophages in a sample?

    <p>Immune-mediated disorders</p> Signup and view all the answers

    In which phase is the myeloblastic series most abundant?

    <p>Proliferative pool</p> Signup and view all the answers

    What percentage of the total erythroid cells does the prorubricyte stage typically represent?

    <p>65%-75%</p> Signup and view all the answers

    What type of leukemia may complicate the identification of the hemodiluted samples?

    <p>Monocytic leukemia</p> Signup and view all the answers

    Which of the following does NOT typically increase the complexity of sample evaluation for hemodilution?

    <p>High red blood cell count</p> Signup and view all the answers

    What is the composition of the segmented neutrophils in the myeloid series?

    <p>80%-85%</p> Signup and view all the answers

    What characteristic is true for metamyelocytes compared to myelocytes?

    <p>Metamyelocytes have a kidney-bean shaped nucleus.</p> Signup and view all the answers

    How do band neutrophils differ from segmented neutrophils?

    <p>Band neutrophils have horseshoe-shaped nuclei.</p> Signup and view all the answers

    What is a distinguishing feature of osteoblasts compared to osteoclasts?

    <p>Osteoblasts appear larger than plasma cells.</p> Signup and view all the answers

    Which cell type is primarily recognized for lysis of bone?

    <p>Osteoclasts</p> Signup and view all the answers

    What best describes the appearance of monocytes in peripheral blood compared to bone marrow?

    <p>Monocytes in peripheral blood appear identical to their bone marrow counterparts.</p> Signup and view all the answers

    What does a decreased myeloid to erythroid (M:E) ratio indicate?

    <p>Increased RBC production</p> Signup and view all the answers

    Which condition is suggested by disorderly maturation of cells?

    <p>Immune-mediated hemolytic anemia</p> Signup and view all the answers

    An increased M:E ratio primarily suggests which of the following?

    <p>Decreased RBC production</p> Signup and view all the answers

    What percentage of mature cells, such as metamyelocytes and bands, should ideally be observed in a normal sample?

    <p>80% to 90%</p> Signup and view all the answers

    Which of the following is NOT a typical indication of increased myeloid cell production?

    <p>High erythropoietin levels</p> Signup and view all the answers

    What does the presence of spherocytes in a blood sample predominantly suggest?

    <p>Immune-mediated hemolytic anemia</p> Signup and view all the answers

    Eccentrocytes in a blood sample are associated with which mechanism of RBC damage?

    <p>Oxidative damage</p> Signup and view all the answers

    Which of the following statements about rouleaux formation is accurate?

    <p>It is normal in horses and enhanced by increased plasma protein concentration.</p> Signup and view all the answers

    Leptocytes are characterized by what distinct feature?

    <p>Excess membrane relative to internal contents</p> Signup and view all the answers

    What is the primary consequence of agglutination of red blood cells?

    <p>Formation of clumps of RBCs</p> Signup and view all the answers

    What characterizes the staining of neutrophils in different species?

    <p>Cows exhibit faint pink granules in neutrophils.</p> Signup and view all the answers

    In which situation do eccentrocytes often appear?

    <p>During oxidative damage to RBCs</p> Signup and view all the answers

    Which of the following best describes the feature of polychromatophilic erythrocytes?

    <p>They indicate a regenerative response in anemia.</p> Signup and view all the answers

    What should be suspected if a steroid response is absent in a sick dog?

    <p>Hypoadrenocorticism</p> Signup and view all the answers

    In the evaluation of neutrophilia, what should be examined if there is no left shift present?

    <p>Lymphocyte numbers</p> Signup and view all the answers

    Which abnormality indicates the presence of lymphocytic leukemia?

    <p>Large-diameter, lighter-staining nucleus</p> Signup and view all the answers

    What is the primary feature of rubriblasts in the erythroid cell maturation sequence?

    <p>Presence of several nucleoli</p> Signup and view all the answers

    What condition can lead to lymphopenia necessitating consideration of a steroid response?

    <p>Stress or excitement</p> Signup and view all the answers

    In horses, why is bone marrow evaluation particularly important?

    <p>To determine if anemia is regenerative</p> Signup and view all the answers

    What is characteristic of erythroid cells as they mature?

    <p>Nuclei size decreases and chromatin becomes denser</p> Signup and view all the answers

    What is the expected quality of lymphocytes during an excitement response?

    <p>Normal appearance with increased numbers</p> Signup and view all the answers

    Which statement about lymphocytes is true?

    <p>Normal lymphocytes have a smaller diameter than neutrophils.</p> Signup and view all the answers

    What distinguishes regenerative anemia from nonregenerative anemia?

    <p>The presence of immature RBCs circulating in the bloodstream.</p> Signup and view all the answers

    What does a high concentration of reticulocytes indicate?

    <p>A regenerative bone marrow response to anemia.</p> Signup and view all the answers

    Which of the following correctly describes the features of monocytes?

    <p>They participate in the inflammatory response by migrating into tissues.</p> Signup and view all the answers

    What is the significance of MCHC levels in hemolytic conditions?

    <p>MCHC can be falsely elevated due to intravascular hemolysis.</p> Signup and view all the answers

    What does the presence of granular lymphocytes indicate?

    <p>An increase in natural killer or T cell activity.</p> Signup and view all the answers

    Which assertion about hyperchromic anemias is correct?

    <p>Hyperchromic anemias do not occur as a distinct category.</p> Signup and view all the answers

    What characteristic is commonly seen in reactive lymphocytes?

    <p>They have a basophilic cytoplasm and irregular nuclear shape.</p> Signup and view all the answers

    Which specific characteristic distinguishes microcytic anemia?

    <p>Decreased mean corpuscular volume (MCV)</p> Signup and view all the answers

    Heinz bodies are indicative of which condition in red blood cells?

    <p>Oxidative damage</p> Signup and view all the answers

    The presence of which pathogens is linked to dark blue inclusions in red blood cells?

    <p>Babesia species</p> Signup and view all the answers

    What type of inclusion characterizes Cytauxzoon felis in infected red blood cells?

    <p>Signet-ring shaped structures</p> Signup and view all the answers

    What classification of anemia is primarily linked to disorders in bone marrow?

    <p>Primary erythrocytosis</p> Signup and view all the answers

    Which condition is described by the presence of paired or single RBC inclusions?

    <p>Babesia infections</p> Signup and view all the answers

    What appearance is indicative of Heinz bodies when viewed under a microscope without staining?

    <p>Small, pale structures at the RBC margins</p> Signup and view all the answers

    Which of the following best describes the appearance of anemic red blood cells due to iron deficiency?

    <p>Small and hypochromic</p> Signup and view all the answers

    What does the presence of echinocytes indicate regarding the condition of red blood cells?

    <p>Artifact from smear preparation</p> Signup and view all the answers

    Howell-Jolly bodies in red blood cells are indicative of which condition?

    <p>Suppressed splenic function</p> Signup and view all the answers

    Siderotic granules in red blood cells typically indicate what underlying issue?

    <p>Impaired heme synthesis</p> Signup and view all the answers

    What abnormality is characterized by the presence of spiculated projections on red blood cells?

    <p>Acanthocytosis</p> Signup and view all the answers

    In which scenario would nucleated red blood cells most likely be found in peripheral circulation?

    <p>Regenerative anemia</p> Signup and view all the answers

    What is the primary association of basophilic stippling in red blood cells?

    <p>Lead poisoning</p> Signup and view all the answers

    Which of these conditions can contribute to the formation of siderocytes in red blood cells?

    <p>Chloramphenicol exposure</p> Signup and view all the answers

    What might be suggested if nucleated red blood cells are observed during a blood examination?

    <p>Active regenerative response</p> Signup and view all the answers

    What condition can lead to a falsely low white blood cell (WBC) concentration?

    <p>Splenic contraction</p> Signup and view all the answers

    Which factor is typically associated with neutrophilia in inflammation?

    <p>Left shift of neutrophils</p> Signup and view all the answers

    What is a characteristic change associated with neutropenia due to severe inflammation?

    <p>Neutrophil consumption exceeding marrow capacity</p> Signup and view all the answers

    Which option describes a typical scenario accompanying inflammatory conditions?

    <p>Nonregenerative anemia and thrombocytopenia</p> Signup and view all the answers

    What condition can contribute to irreversible neutropenia?

    <p>Viral infections such as FeLV</p> Signup and view all the answers

    What factor may contribute to the variations in bone marrow response to inflammation across species?

    <p>Species-specific bone marrow reserve capacity</p> Signup and view all the answers

    What causes neutropenia with a left shift when inflammation is present?

    <p>Excessive consumption of neutrophils</p> Signup and view all the answers

    What might be a cause of mild increases in packed cell volume (PCV)?

    <p>Excitement or exercise</p> Signup and view all the answers

    What is the primary difference between Type I and Type II myeloblasts?

    <p>Type I myeloblasts have no azurophilic granules.</p> Signup and view all the answers

    Identify the true statement regarding promyelocytes based on their cytoplasmic characteristics.

    <p>Promyelocytes contain many azurophilic granules.</p> Signup and view all the answers

    Which of the following statements best describes the cytoplasmic characteristics of myelocytes?

    <p>Myelocytes exhibit no primary granules and have a rounded nucleus.</p> Signup and view all the answers

    What is a distinguishing feature of granulocytes compared to other white blood cells?

    <p>They have irregularly shaped nuclei characterized by fine chromatin patterns.</p> Signup and view all the answers

    Which of the following best describes the characteristics of macrophages?

    <p>Their cytoplasm appears gray-blue and often vacuolated.</p> Signup and view all the answers

    What is considered a primary characteristic of megakaryocytes?

    <p>These cells are very large and have interconnected nuclei.</p> Signup and view all the answers

    Which feature is typical for the maturation sequence of myeloid cells?

    <p>Myeloblasts mature into band neutrophils in a linear sequence.</p> Signup and view all the answers

    Identifying which type of cell may suggest a lymphoproliferative disorder is associated with which cells?

    <p>Lymphoblasts</p> Signup and view all the answers

    What is a defining characteristic of metarubricytes in terms of their size and cellular content?

    <p>They are smaller than rubricytes and still contain a nucleus.</p> Signup and view all the answers

    Which feature is unique to polychromatophilic erythrocytes when stained with methylene blue?

    <p>They are blue-pink and may contain nuclear remnants.</p> Signup and view all the answers

    Which statement correctly describes granulocyte (myeloid) cells?

    <p>They are derived from stem cells and play a role in immune response.</p> Signup and view all the answers

    What distinguishes megakaryocytes from other hematopoietic cells in terms of size?

    <p>They are the largest hematopoietic cells with a distinct maturation process.</p> Signup and view all the answers

    In the context of acute inflammatory changes, what does a left shift refer to?

    <p>An increase in immature neutrophils in the peripheral blood.</p> Signup and view all the answers

    What type of transition occurs in the maturation of normoblasts to reticulocytes?

    <p>The complete loss of all cellular organelles.</p> Signup and view all the answers

    Which of the following statements is true regarding acute inflammatory consumption?

    <p>It is characterized by the presence of toxic changes in neutrophils.</p> Signup and view all the answers

    What is the typical appearance of erythroblasts transitioning into more mature stages of erythropoiesis?

    <p>Erythroblasts gain a more basophilic staining as they mature.</p> Signup and view all the answers

    Which feature is characteristic of metamyelocytes compared to myelocytes?

    <p>They possess kidney-bean shaped nuclei.</p> Signup and view all the answers

    What is the distinguishing cytological feature of band neutrophils?

    <p>They have horseshoe-shaped nuclei.</p> Signup and view all the answers

    What indicates that osteoclasts are specialized macrophages?

    <p>They lyse bone tissue.</p> Signup and view all the answers

    How do macrophages typically appear when they accumulate hemosiderin?

    <p>They present with a reddish-brown pigmentation.</p> Signup and view all the answers

    What is true about the maturity sequence of monocytes in the bone marrow?

    <p>Monocytes appear identical in bone marrow and peripheral blood.</p> Signup and view all the answers

    Which cell type is characterized by having irregularly sized spicules on the surface and is commonly seen in cholestatic liver disease?

    <p>Acanthocytes</p> Signup and view all the answers

    What do Howell-Jolly bodies signify in a blood smear?

    <p>Suppressed splenic function</p> Signup and view all the answers

    Which of the following is NOT associated with the formation of echinocytes?

    <p>Chloramphenicol exposure</p> Signup and view all the answers

    What condition is associated with the presence of basophilic stippling in red blood cells?

    <p>Lead poisoning</p> Signup and view all the answers

    What do siderotic granules in red blood cells indicate?

    <p>Presence of iron granules</p> Signup and view all the answers

    Which type of cell abnormality is typically a sign of regenerative anemia?

    <p>Nucleated red blood cells</p> Signup and view all the answers

    What are siderocytes commonly associated with?

    <p>Myelodysplasia</p> Signup and view all the answers

    Which of the following cell types remains in circulation with a retained nucleus, often indicating regenerative states?

    <p>Nucleated red blood cells</p> Signup and view all the answers

    What does an increased M:E ratio suggest in a hematological evaluation?

    <p>Increased myeloid cell production</p> Signup and view all the answers

    Which condition is indicated by disorderly maturation of hematopoietic cells?

    <p>Leukemia</p> Signup and view all the answers

    What is the typical range for the percentage of mature cells, such as metamyelocytes and bands, in a normal sample?

    <p>80% to 90%</p> Signup and view all the answers

    What does a decreased M:E ratio imply regarding hematopoietic activity?

    <p>Decreased myeloid cell production</p> Signup and view all the answers

    Which of the following conditions is NOT typically associated with an increased M:E ratio?

    <p>Increased erythropoiesis</p> Signup and view all the answers

    What cellular characteristic is commonly seen with hemangiosarcoma?

    <p>Acanthocytes and schistocytes</p> Signup and view all the answers

    Which condition is associated with reticulocytosis and polychromasia?

    <p>Acute blood loss</p> Signup and view all the answers

    What is a common finding in chronic blood loss?

    <p>Microcytosis and increased RDW</p> Signup and view all the answers

    Eosinophils participate in which type of responses?

    <p>Inflammatory and immune responses</p> Signup and view all the answers

    What is the primary feature of basophils?

    <p>Containment of histamine and heparin</p> Signup and view all the answers

    What morphological feature distinguishes cat eosinophils from other species?

    <p>Rod- or barrel-shaped granules</p> Signup and view all the answers

    Which type of anemia is characterized by the presence of spherocytes?

    <p>Hemolytic anemia</p> Signup and view all the answers

    What is a characteristic feature of erythrocyte parasites like Mycoplasma species?

    <p>Attachment to RBC membrane</p> Signup and view all the answers

    What is the first step to assess neutrophilia in a sick dog?

    <p>Check for left shift in neutrophils</p> Signup and view all the answers

    In horses, what is a key factor in determining if anemia is regenerative?

    <p>Bone marrow evaluation results</p> Signup and view all the answers

    What does lymphopenia in a sick dog typically suggest?

    <p>Possible steroid response</p> Signup and view all the answers

    Which characteristic best distinguishes rubriblasts in the erythroid series?

    <p>Presence of multiple nucleoli</p> Signup and view all the answers

    What abnormality is indicated by the presence of lymphocytosis in patients?

    <p>Viral infections or leukemias</p> Signup and view all the answers

    What does a lack of a left shift in neutrophils suggest during the evaluation of a sick dog?

    <p>Excitement response may be present</p> Signup and view all the answers

    What morphological feature defines a metarubricyte within erythroid cells?

    <p>Round nucleus with gradually condensed chromatin</p> Signup and view all the answers

    In the context of neutrophilia, what does the presence of large-diameter lymphocytes indicate?

    <p>Lymphocytic leukemia</p> Signup and view all the answers

    Study Notes

    Plasma Protein Concentration

    • Determined by refractometry
    • Hyperlipemia can falsely increase concentration by 2 g/dL

    Total Leukocyte Concentration

    • Measured using Unopette dilutions or instruments designed for particle counting
    • Detects all nuclei in solution, including nucleated RBCs

    Hemoglobin Concentration

    • An index of RBC mass per unit volume of blood
    • Provides information similar to PCV
    • In most species (except camels), hemoglobin concentration is about a third of the PCV

    Mean Cell Volume (MCV)

    • Reflects RBC size
    • Macrocytic: Suggests increased red cell turnover
      • Some toy poodles, miniature poodles, and greyhounds may have macrocytic RBCs
    • Microcytic: Suggests defective red cell growth
      • Akita and Shiba Inu dogs may have microcytic RBCs
    • Normocytic: Red cell size is unchanged
    • Dogs have the highest MCV values (largest RBCs)
    • Sheep, llamas, and goats have the lowest MCV values (smallest RBCs)

    Mean Corpuscular Hemoglobin (MCH) and Mean Corpuscular Hemoglobin Concentration (MCHC)

    • Used to classify anemia

    RBC Morphology

    • Changes in Size:
      • Anisocytosis: Variation in RBC size
      • Microcytic RBCs: Smaller than normal, with decreased MCV
      • Macrocytic RBCs: Larger than normal, with increased MCV
    • Changes in Shape (Poikilocytosis):
      • Poikilocytes: Abnormally shaped RBCs
      • Schistocytes: RBC fragments, usually caused by intravascular trauma
      • Keratocytes: RBCs with two or more spicules
      • Acanthocytes (Spur Cells): Irregular, spiculated RBCs with unevenly distributed surface projections
        • May result from changes in cholesterol or phospholipid concentrations in the RBC membrane
        • Commonly seen in cats with hepatic lipidosis and dogs with hemangiosarcoma
    • Changes in Color:
      • Polychromasia: Presence of young erythrocytes (larger and slightly bluer) - Degree of polychromasia correlates with reticulocyte response
      • Hypochromic RBCs: Pale, with decreased hemoglobin concentration (usually from iron deficiency)
    • Structures in or on RBCs:
      • Heinz bodies: Caused by oxidant damage, denaturation of hemoglobin, appear as small, pale structures near the margin of RBCs (may protrude)
      • Basophilic Stippling: Aggregation of ribosomes into small granules, caused by membrane folding - target cell formation (codocytes)
      • Codocytes: Thin and bowl-shaped with a dense central area of hemoglobin (target appearance) - May be seen in animals with increased serum cholesterol concentrations
      • Stomatocytes: RBCs with a mouthlike clear area in the center - Found in dogs with hereditary stomatocytosis

    Reticulocytes

    • Corrected percentage for a reticulocyte value greater than 1% indicates RBC regeneration
    • Count greater than 60,000 cells/L indicates RBC regeneration
    • Takes at least 3 days for reticulocytes to appear in the circulation
    • Horses do not release reticulocytes

    Rouleau and Agglutination

    • Rouleau: Stacking of RBCs resembling a roll of coins, can occur in normal conditions but may change in response to inflammation
    • Agglutination: Clumping of RBCs, indicates autoimmune hemolytic anemia

    Anemia Types

    • Regenerative: Increased reticulocyte count
    • Nonregenerative: Normal or decreased reticulocyte count
      • Normochromic: Normal MCHC
      • Hypochromic: Decreased MCHC
      • Normocytic: Normal MCV
      • Microcytic: Decreased MCV
      • Macrocytic: Increased MCV

    Bone Marrow Collection

    • Common sites:
      • Large Dogs: Dorsal approach to the iliac crest
      • Small Dogs and Cats:
        • Lateral approach to the wing of the ilium for core biopsies
        • Trochanter fossa of proximal femur for aspiration biopsies
        • Proximal humerus for both aspiration and core biopsies

    Bone Marrow Cells

    • Myeloid Cells:
      • Myeloblasts: 5% of ancestral myeloid cells (AMC)
      • Progranulocytes, Myelocytes: 15% of AMC
      • Metamyelocytes, Bands: 80-85% of AMC
    • Erythroid Cells:
      • Rubriblasts: 5% of ancestral erythroid cells (AEC)
      • Prorubricytes, Rubricytes: 65-75% of AEC
      • Metarubricytes: 20-30% of AEC
    • Megakaryocyte Cells:
      • Maturation sequence: Megakaryoblasts, promegakaryocytes, megakaryocytes
      • Megakaryoblasts are larger than any other types of precursors
    • Other Cells:
      • Macrophages: Usually present in small numbers, increased numbers may indicate immune-mediated disorders
    • Myeloid:Erythroid (M:E) Ratio:
      • Approximately 0.5:1 to 3:1
      • Hemodiluted samples are difficult to evaluate

    Cytochemistry and Immunophenotyping

    • Provide additional information for bone marrow analysis

    Red Blood Cell Morphology

    • Spherocytes: Dark-staining RBCs without central pallor. Most easily identified in dogs. Suggest immune-mediated hemolytic anemia
    • Eccentrocytes: Hemoglobin shifted to one side, clear eccentric zone. Indicate oxidative damage and may occur with Heinz bodies.
    • Leptocytes: Excess membrane relative to internal contents, may occur in vitro with excess EDTA.
    • Rouleaux Formation: Stacking of RBCs, normal in horses, enhanced with increased plasma protein concentration
    • Agglutination: Clumps of RBCs, associated with immune-mediated hemolytic anemia

    Leukocytes

    • Neutrophils: Contain small granules in cytoplasm that stain differently in different species
    • Lymphocytes: Responsible for immune responses, have a round to oval nucleus with minimal clear cytoplasm
    • Monocytes: Participate in inflammation, migrate into tissues and develop

    Anemia

    • Hypochromic Anemia: RBCs contain less hemoglobin than normal (decreased MCHC)
    • Normochromic Anemia: RBCs contain a normal amount of hemoglobin (normal MCHC)
    • Hyperchromic Anemia: Does not occur, MCHC can be falsely elevated with intravascular hemolysis

    Anemia Responsiveness

    • Regenerative Anemia: Increased number of immature RBCs circulating, indicating increased RBC production. Reticulocyte count greater than 60,000 cells/L
    • Nonregenerative Anemia: No increase in immature RBCs, indicates lack of bone marrow response

    Bone Marrow Evaluation

    • Indications: Nonregenerative anemia, neutropenia, thrombocytopenia, gammopathies, possible neoplastic marrow disease.
    • Horses: Useful for determining if anemia is regenerative because horses don't release reticulocytes
    • Sites: Ilium, ribs, sternum in horses, cattle, camelids.
    • Erythroid Cells: Round nuclei, moderate to deep blue cytoplasm, pinker as hemoglobin is produced
    • Erythroid Cell Maturation: Rubriblast -> prorubricyte -> rubricyte -> metarubricyte -> polychromatophilic erythrocyte -> mature erythrocyte
    • Other Cell Types: Macrophages, osteoblasts, osteoclasts, mast cells
    • Interpretation:
      • 50% cells and 50% fat is normal
      • Decreased M:E ratio suggests increased RBC production, decreased neutrophils, or both
      • Increased M:E ratio suggests increased myeloid cell production, decreased RBC production, or both

    Neutrophilia

    • Left Shift: Presence of immature neutrophils (bands, metamyelocytes, myelocytes) indicates inflammation
    • No Left Shift: Consider lymphopenia, indicating a steroid response, possibly combined with inflammation
    • Normal or Increased Lymphocytes: Consider excitement response

    Lymphocytosis

    • Excitement Response: Lymphocytes appear normal
    • Lymphocytic Leukemia: Abnormal morphology, including large diameter and light staining nucleus, visible nucleoli, increased cytoplasm
    • Chronic Canine Ehrlichiosis: Secondary granules present, eosinophilic precursors have pink granules, basophilic precursors have purple granules

    Monocyte Cells

    • Difficult to Distinguish: From Myeloid Series, monocyte cells have irregular nuclear outlines
    • Maturation Sequence: Monoblasts -> promonocytes -> monocytes
    • Bone Marrow Appearance: Same as peripheral blood. Precursors are difficult to identify.

    Acanthocytes

    • Blood smear from a dog with cholestatic liver disease
    • Irregularly sized spicules

    Erythrocyte Inclusions

    • Associated with immature RBCs in ruminants
    • Lead poisoning often causes basophilic stippling
    • Nucleated RBCs are an indication of regenerative anemia, a nonfunctioning spleen, or steroids (endogenous or exogenous)
    • Howell-Jolly bodies are nuclear remnants in RBCs
    • Siderotic granules are visible iron granules in RBCs (siderocytes)

    Anemia

    • Microcytic Anemia
      • RBCs are small (decreased MCV)
      • Usually because of iron deficiency
      • Can be caused by portocaval shunts
    • Macrocytic Anemia
      • RBCs are large (increased MCV)
      • Usually due to vitamin B12 or folate deficiency
      • Can be caused by liver disease

    Polycythemia

    • Secondary Polycythemia
      • Generalized hypoxia
      • Increased erythropoietin production
    • Primary Polycythemia
      • Bone marrow disorder
      • Cells appear normal, and maturation process is normal

    Leukocyte Responses

    • Falsely Low White Blood Cell (WBC) Concentration
      • May cause a mild increase in PCV (not greater than 60%)
      • Causes a mild increase in PCV (not greater than 60%)
    • Lymphocyte Vacuolation
      • May occur after ingestion of swainsonine (locoweed ingestion in horses or cattle)
      • It also occurs in lysosomal storage diseases

    Response to Inflammation

    • Increased demand for leukocytes as a result of consumption
    • Bone marrow should respond by releasing more leukocytes and increasing production
    • Most inflammation is associated with some degree of neutrophilia
    • Severity of inflammation can be predicted by the degree of left shift and the toxic changes present
    • Neutropenia with left shift may occur when the consumption of neutrophils by the inflammatory process exceeds the bone marrow's capacity to produce neutrophils
    • Species variation in the amount of bone marrow reserve to respond to inflammation

    Neutropenia

    • Reversible Neutropenia
      • Typically accompanied by nonregenerative anemia and thrombocytopenia
      • Causes include chemotherapeutic agents, other drugs such as estrogen or phenylbutazone in dogs, and ehrlichiosis
    • Irreversible Neutropenia
      • Causes include feline leukemia virus (FeLV), hypoproliferative disorders, myelodysplasias, and myeloproliferative disorders

    Bone Marrow Cells

    • Erythrocyte Precursors
      • Prorubricytes - Largest of the erythrocyte precursors - Nucleus is round to oval with a fine chromatin pattern and nucleoli that are visible - Cytoplasm is blue-gray
      • Rubricytes - Can still undergo mitosis - Smaller than prorubricytes - Very coarse chromatin - Polychromatophilic cytoplasm
      • Metarubricytes - Still contain a nucleus - Smaller than rubricytes - Polychromatophilic cytoplasm
      • Polychromatophilic erythrocytes - Do not contain a nucleus - Blue-pink - May contain nuclear remnants (Howell-Jolly bodies) - When stained with methylene blue and reticulum is visible, they are termed reticulocytes
    • Granulocyte (Myeloid) Cells
      • Granulocytes - Irregularly shaped nuclei with fine chromatin patterns and lavender cytoplasm
      • Maturation Sequence - Myeloblast, promyelocyte, myelocyte, metamyelocyte, band neutrophil, segmented neutrophil
      • Type I myeloblasts - Most immature - Round to oval nucleus - Nucleoli - Small amount of blue-staining cytoplasm - No azurophilic granules - Cytoplasm has a ground glass appearance and may contain small vacuoles
      • Type II myeloblasts - Contain a few azurophilic granules (primary granules) in the cytoplasm - Otherwise appear similar to type I myeloblasts
      • Promyelocytes - Many azurophilic granules in the cytoplasm - Nucleus is central to eccentric - Nucleoli are present
      • Myelocytes - Can still undergo mitosis - Smaller than promyelocytes - Light blue cytoplasm - No primary granules - Nuclei are round to oval
    • Megakaryocyte Cells
      • Derived from stem cells
      • Maturation Sequence - Megakaryoblasts, promegakaryocytes, megakaryocytes
      • Megakaryoblasts - Larger than any other types of precursors
      • Promegakaryocytes - Two to four nuclei with a deep blue cytoplasm
      • Megakaryocytes - Very large - Numerous nuclei that are connected - Cytoplasm becomes granular and is sometimes light pink
    • Other Cells
      • Lymphocytes - Appear as they do in the peripheral circulation
      • Plasma Cells - Differentiated lymphocytes that produce immunoglobulin - Look similar to rubricytes, but the cytoplasm is more abundant in plasma cells and they have a clear perinuclear Golgi zone
      • Lymphoblasts - Rare - May indicate a lymphoproliferative disorder
      • Macrophages - Derived from monocytes - In low numbers in bone marrow - Cytoplasm is usually vacuolated, is gray-blue, and may contain small pink granules

    Bone Marrow Collection Sites

    • Dogs
      • Dorsal approach to the iliac crest
      • Lateral approach to the wing of the ilium
      • Trochanter fossa of proximal femur
      • Proximal humerus
    • Cats
      • Lateral approach to the wing of the ilium
      • Trochanter fossa of proximal femur
      • Proximal humerus

    Erythrocyte Morphology

    • Acanthocytes have irregularly sized spicules, are commonly seen in cholostatic liver disease, and are also seen with hemangiosarcoma
    • Echinocytes (burr cells) have evenly distributed blunt to sharp surface projections
      • May be an artifact from slow drying of a blood smear
      • Seen in renal disease, lymphoma, rattlesnake envenomation, and when RBCs are engulfed by macrophages
    • Commonly Misidentified Cells
      • Spherocytes are characterized by a lack of central pallor
      • Schistocytes are fragmented RBCs
      • Basophilic Stippling is associated with immature RBCs in ruminants and lead poisoning
    • Nucleated RBCs are RBCs in the circulation that have retained their nucleus
      • Indicate regenerative anemia, a nonfunctioning spleen, or steroid use (endogenous or exogenous)
    • Howell-Jolly Bodies are nuclear remnants in RBCs that appear as dark staining, round inclusions, and are associated with regenerative anemia or suppressed splenic function
    • Siderotic Granules are visible iron granules in RBCs (siderocytes), associated with chloramphenicol, myelodysplasia, and impaired heme synthesis

    Anemia

    • Acute Blood Loss
      • Acanthocytes, schistocytes, reticulocytosis, polychromasia, and thrombocytopenia are commonly present
    • Chronic Blood Loss
      • Iron deficiency anemia
      • Decreased MCV (microcytosis), increased RDW, MCHC usually normal
      • Keratocytes and schistocytes are common
    • Blood Destruction
      • Immune-mediated hemolytic anemia
      • Neonatal isoerythrolysis
      • Erythrocyte parasites
        • Mycoplasma: haemofelis (cats), haemocanis (dogs), wenyonii (cattle), haemosuiss (swine), Candidatus Mycoplasma haemolamae (llamas and alpacas)
        • Anaplasma marginale (cattle)
      • Spherocytes are common

    Bone Marrow

    • Bone Marrow Aspirate sites:
      • Dogs and cats: Femur, humerus, or iliac crest
      • Horses, cattle, camelids: Ilium, ribs, or sternum
    • Indications: Nonregenerative anemia, neutropenia, thrombocytopenia, gammopathies, and possible neoplastic marrow disease
    • Horses: Bone marrow evaluation is essential to determine if anemia is regenerative

    Erythroid Cells

    • Erythroid cells have round nuclei and moderate to deep blue cytoplasm that becomes pinker as hemoglobin is produced
    • Maturation sequence (immature to mature): Rubriblast, prorubricyte, rubricyte, metarubricyte, polychromatophilic erythrocyte, mature erythrocyte, and polychromasia
    • Rubriblasts are large with round nuclei, slightly coarse chromatin, and nucleoli. Little cytoplasm that stains deep blue
    • Prorubricytes lack nucleoli, are smaller than rubriblasts, and have a little more cytoplasm
    • Metarubricytes have condensed, darkly stained nuclei and a small rim of cytoplasm
    • Polychromatophilic Erythrocytes have a thin, well-defined rim of blue cytoplasm, a centrally placed, round nucleus, and less chromatin than a metarubricyte
    • Mature Erythrocytes are fully hemoglobinized and lack a nucleus. They have a central pallor

    Other Bone Marrow Cells

    • Myeloid Cells (derived from stem cells)
      • Difficult to distinguish from monocyte cells
      • Maturation sequence (immature to mature): Myeloblasts, promyelocytes, myelocytes, metamyelocytes, band neutrophils, segmented neutrophils
      • Myeloblasts are the largest of the myeloid cells
      • Promyelocytes are larger than myelocytes and have a nucleus that is round, oval, or bean-shaped. They contain primary granules
      • Myelocytes have round, oval, or kidney-bean-shaped nuclei. They contain secondary granules
      • Metamyelocytes have kidney-bean–shaped nuclei, and are smaller than myelocytes
      • Band neutrophils have horseshoe-shaped nuclei, with cytoplasm similar to segmented neutrophils
      • Segment Neutrophils have a segmented nucleus with 3-5 lobes.
    • Macrophages phagocytize debris and often contain hemosiderin
    • Osteoblasts appear similar to plasma cells, but are larger.
    • Osteoclasts are specialized macrophages that lyse bone, and have a similar appearance to megakaryocytes, but have individual nuclei.
    • Mast Cells are rare, large round cells with numerous metachromatic granules within the cytoplasm

    Interpretation

    • Cellularity: Normally marrow is about 50% cells and 50% fat
      • Decreased M:E Ratio is associated with increased RBC production or decreased neutrophil production
      • Increased M:E Ratio is associated with increased myeloid cell production or decreased RBC production
    • Maturation: Approximately 80% to 90% of the cells should be more mature cells (metamyelocytes, bands, neutrophils; rubricytes, metarubricytes)
      • Disorderly maturation can be seen with leukemia, myeloid hyperplasia, immune-mediated hemolytic anemia, or marked inflammation

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