Laboratory Assessment of Anemia and Erythrocytosis (II)

Vocabulary practice flashcards covering the laboratory differentiation of regenerative and nonregenerative anemias, hemorrhagic and hemolytic conditions, iron deficiency, chronic diseases, and mechanisms of erythrocytosis based on VET 402 Lecture 9.

Regenerative Anemia Timeline

The expected bone marrow response time to anemia or hypoxia, requiring $2\text{ to }4\text{ days}$ to show initial reticulocyte evidence and up to $7\text{ days}$ for robust peak evidence of regeneration.

Protein Pattern in Blood Loss vs. Hemolysis

Blood loss leads to concurrent decrease in total protein (both albumin and globulins lost together with red blood cells), whereas red blood cell destruction maintains total protein within the reference interval.

Biochemical Hallmarks of Hemolysis

Laboratory abnormalities specific to red blood cell destruction rather than hemorrhage, including increased bilirubin, bilirubinuria, hemoglobinemia, and hemoglobinuria.

Hemorrhage (Blood Loss)

The loss of whole blood (both red blood cells and plasma proteins) from the vascular system, manifesting acutely as a regenerative anemia or chronically as regenerative to nonregenerative if progressive iron depletion ensues.

Acute Blood Loss Kinetics

The progression following severe hemorrhage where whole blood is lost together on Day $0$, interstitial fluid replaces plasma volume by Day $1$ ($\sim 24\text{ hr}$) unmasking anemia and hypoproteinemia, reticulocytosis peaks on Day $7$, plasma proteins normalize by Day $7$, and red cell mass normalizes within $2\text{ to }3\text{ weeks}$.

Internal Blood Loss

Bleeding into tissues or internal body cavities where extravasated red blood cells are phagocytosed by macrophages and iron is recycled back into the body, maintaining a regenerative erythroid response.

External Blood Loss

Bleeding out of the body (e.g., via the gastrointestinal tract, urinary tract, or skin parasites), resulting in progressive iron depletion that can cause chronic nonregenerative anemia.

Melena

Dark, tarry stool formed from digested blood originating from upper gastrointestinal hemorrhage, representing a frequent cause of chronic external blood loss and secondary iron deficiency.

Intravascular Hemolysis

Accelerated red blood cell destruction caused by direct cell lysis within the vascular system, resulting in the release of free hemoglobin into the circulating plasma.

Extravascular Hemolysis

Accelerated red blood cell destruction through phagocytosis by macrophages in the spleen, liver, and other organs; it is overall more predominant than intravascular hemolysis.

Haptoglobin

A plasma carrier protein that binds free hemoglobin dimers released during intravascular hemolysis; the complex is recognized by CD163 receptors on macrophages and internalized for heme degradation into bilirubin.

Hemoglobinemia

The presence of excess free hemoglobin in plasma or serum giving it a pink-to-red discoloration, which occurs when intravascular hemolysis overwhelms the binding capacity of haptoglobin.

Hemoglobinuria

The excretion of excess free hemoglobin into urine during severe intravascular hemolysis when plasma haptoglobin is saturated and renal tubular reabsorption capacity is exceeded.

Icterus

Yellow discoloration of plasma, mucous membranes, and tissues resulting from hyperbilirubinemia, commonly caused by marked extravascular hemolysis or hepatobiliary disease.

Immune-Mediated Hemolytic Anemia (IMHA)

A disorder where anti-erythrocyte antibodies ($\text{IgG}$ or $\text{IgM}$) and complement ($\text{C3b}$, membrane attack complex) target red blood cells, causing extravascular phagocytosis via macrophage $\text{Fc}\gamma\text{R}$ and $\text{C3R}$ or intravascular complement lysis.

Spherocytes

Small, dense, spherical erythrocytes that lack central pallor, formed when splenic macrophages partially phagocytose antibody- or complement-coated red cell membranes; hallmark of canine IMHA.

RBC Agglutination

The spontaneous clumping of erythrocytes into irregular clusters caused by antibody cross-linking (particularly $\text{IgM}$), serving as diagnostic evidence for immune-mediated hemolytic anemia.

Heinz Bodies

Aggregates of denatured, oxidized hemoglobin that adhere to the internal red blood cell membrane, appearing as pale refractile bumps on Wright's stain and distinct blue structures on New Methylene Blue stain.

Ghost Cells

Extremely pale, evacuated erythrocyte membranes devoid of internal hemoglobin, characteristic of acute intravascular hemolysis or severe oxidative damage.

Microangiopathic Hemolytic Anemia

Mechanical red blood cell injury and fragmentation occurring when circulating erythrocytes snag and shear against intravascular fibrin strands in microvessels.

Schistocytes

Irregularly shaped, sharp erythrocyte fragments formed by mechanical shearing against intravascular fibrin strands or turbulent blood flow.

Keratocytes

Erythrocytes with helmet-shaped appearances or paired spicules, formed after mechanical fragmentation or the rupture of a peripheral pseudovacuole blister.

Nonregenerative Anemia

Anemia resulting from decreased or ineffective erythropoiesis, characterized by an inadequate reticulocyte response, minimal polychromasia, and absent-to-few nucleated red blood cells on blood smear.

Anemia of Inflammation

The most common form of nonregenerative anemia in animals, characterized by mild normocytic-normochromic indices, increased bone marrow macrophage iron, elevated hepcidin, blunted EPO production/response, and shortened RBC survival.

Hepcidin

A liver-produced peptide hormone elevated in inflammatory states that sequesters iron within storage macrophages and blocks dietary iron absorption in the intestine.

Prussian Blue Stain

A special histochemical stain used to visualize bone marrow hemosiderin reserves, showing abundant iron in macrophages in anemia of inflammation and absent iron in iron deficiency.

Anemia of Chronic Kidney Disease

A moderate to severe normocytic-normochromic nonregenerative anemia caused primarily by decreased erythropoietin ($\text{EPO}$) production by failing kidneys, along with decreased hepcidin excretion and uremic toxins.

Iron Deficiency Anemia

An anemia classically presenting with microcytic-hypochromic red blood cells ($\downarrow\text{MCV}$, $\downarrow\text{MCHC}$), target cells, keratocytes, schistocytes, and often thrombocytosis, caused by chronic external blood loss or deficient dietary intake.

Extra Cell Division in Iron Deficiency

The pathophysiologic mechanism where developing erythroid precursors undergo an extra mitotic division in an attempt to reach target intracellular hemoglobin concentrations, resulting in microcytosis.

Myelophthisis

The crowding out, displacement, or replacement of normal hematopoietic bone marrow elements by abnormal proliferating cells (e.g., neoplasia, inflammation, or myelofibrosis), leading to nonregenerative anemia and concurrent cytopenias or pancytopenia.

Dacrocytes

Teardrop-shaped red blood cells visible on blood films that are characteristically associated with primary bone marrow pathology, such as myelofibrosis.

Erythrocytosis

An elevation in circulating red blood cell mass, measured clinically as an increased hematocrit ($\text{HCT}$), red blood cell count, or hemoglobin concentration.

Relative Erythrocytosis

An increased hematocrit ($\text{HCT}$) without an actual increase in total red blood cell mass, typically caused by dehydration (accompanied by elevated plasma proteins) or transient epinephrine-mediated splenic contraction (common in horses and cats).

Absolute Erythrocytosis

A true, documented expansion of total circulating red blood cell mass, classified as primary (autonomous erythroid neoplasia) or secondary (erythropoietin-mediated).

Polycythemia Vera

A primary absolute erythrocytosis caused by autonomous red blood cell neoplasia occurring independently of erythropoietin ($\text{EPO}$) regulation.

Secondary Absolute Erythrocytosis

An absolute increase in red blood cell mass driven by increased erythropoietin ($\text{EPO}$) production, which may be an appropriate response to chronic tissue hypoxia (e.g., high altitude, chronic cardiopulmonary disease) or inappropriate secretion by renal cysts or rare tumors.