How do you differentiate regenerative vs non-regenerative anemia in a dog?

• A. Reticulocytosis, polychromasia, and anisocytosis.
• B. Low reticulocyte count with microcytosis.
• C. Lack of polychromasia.
• D. Thrombocytopenia.

Answer: (A)

The key idea is recognizing a bone marrow response to anemia. When the body is regenerating red blood cells, the marrow releases young cells into the bloodstream, so you see signs of erythroid production on the smear.

Reticulocytosis means there are more immature red blood cells circulating. On a peripheral smear, these immature cells show up as polychromasia—a bluish tinge from residual RNA—and there is anisocytosis, a mix of cell sizes from newly released reticulocytes and older cells. Together, these findings indicate the marrow is actively compensating for anemia by producing and delivering new RBCs.

In contrast, a low reticulocyte count with microcytosis suggests a non-regenerative process or a specific cause like iron deficiency, where the marrow isn’t mounting a robust reticulocyte response. Absence of polychromasia points to a lack of recent marrow activity. Thrombocytopenia involves platelets, not red cell regeneration, so it doesn’t inform about erythropoiesis.