Causes 

• Anemia can happen when there's:

  • Loss of RBCs (e.g., bleeding or destruction of red blood cells)

  • Inadequate RBC production (due to bone marrow issues or low erythropoietin)

  • Destruction of RBCs (e.g., hemolysis)

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Types of Anemia

• Regenerative Anemia:

  • The bone marrow responds to anemia by making more RBCs and releasing reticulocytes (immature RBCs).

  • This happens quickly after acute blood loss or hemolysis (RBC destruction).

  • Macrocytosis (larger RBCs) usually shows up, indicating a regenerative response.

  • This response takes about 3–5 days to be noticeable.

• Nonregenerative Anemia:

  • The bone marrow doesn’t respond well to anemia.

  • Causes can include bone marrow failure, chronic illness, or insufficient erythropoietin (a hormone that stimulates RBC production).

  • The marrow isn't making enough RBCs even though the body needs them.

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Clinical Signs

• Acute Anemia:

  • Occurs after rapid blood loss (more than 1/3 of blood volume).

  • Common signs:

    • Tachycardia (fast heart rate)

    • Pale gums

    • Weak or bounding pulses

    • Low blood pressure (hypotension)

  • Can be caused by trauma, internal bleeding, or conditions like coagulopathy (bleeding disorders).

  • Hemolysis (RBC destruction) can cause jaundice (yellowing of the skin and mucous membranes).

• Chronic Anemia:

  • Happens slowly, so animals may not show severe symptoms right away.

  • Symptoms can include:

    • Lethargy (tiredness)

    • Weakness

    • Loss of appetite (anorexia)

  • The body adjusts over time, so signs can be less obvious.

  • Sometimes, signs like enlarged spleen or heart murmurs can point to the underlying cause.

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Diagnosis

• History:

  • A thorough history is essential to understand the cause (e.g., past illnesses, toxin exposure, medications, or surgeries).

• Blood Tests:

  • CBC (Complete Blood Count): Helps measure how severe the anemia is and checks how the bone marrow is responding (reticulocytes and platelets).

  • Blood Smear: A close look at RBCs for abnormalities (e.g., parasites, agglutination, or signs of injury like Heinz bodies).

  • RBC Indices (e.g., MCV and MCHC):

    • MCV: Measures RBC size; larger cells usually mean regenerative anemia.

    • MCHC: Measures how much hemoglobin (the protein that carries oxygen) is in each RBC.

  • Reticulocyte Count: Helps determine how well the bone marrow is producing new RBCs.

    • Regenerative anemia: Absolute reticulocyte count >50,000/mcL in cats or >60,000/mcL in dogs, or a corrected reticulocyte percentage >1%.

    • Takes 3–4 days after blood loss or hemolysis to show up.

• Protein Levels:

  • Low protein levels often suggest blood loss; normal or high protein levels are seen in hemolysis.

• Other Tests:

  • A biochemistry panel and urinalysis can help assess overall organ function and detect issues like kidney damage from blood loss.

  • X-rays may help find hidden causes like foreign objects (e.g., zinc poisoning).

• Bone Marrow Evaluation:

  • Needed if the cause of anemia is unclear and the bone marrow isn’t responding.

  • A biopsy can help assess the marrow’s architecture and cellular makeup, while an aspiration lets us see how RBCs and other blood cells are maturing.

• Bone Marrow Assessment:

  • MRatio (Myeloid to Erythroid Ratio):

    • A ratio less than 1 means the bone marrow is making more RBCs than white blood cells.

    • A ratio higher than 1 means the opposite.

    • This ratio is interpreted with other tests to help understand what’s going on in the bone marrow.