Distinguishing Canine Leukocyte Increase and Decrease:
During the early stages of the illness, there is an increase in total white blood cell count, with a higher proportion of neutrophils and a shift to the left in the nuclear pattern, manifesting as a significant presence of bandshaped and immature nuclei, indicating a proliferative left shift. In later cases, the total white blood cell count tends to decrease, with minimal change in the proportion of neutrophils and a left shift in the nuclear pattern, known as a regressive left shift. Relative erythrocytosis may occur due to dehydration and circulatory failure, characterized by thickened blood, slower erythrocyte sedimentation rate, and an increased hematocrit over 40%.
Metabolic acidosis may develop, marked by decreased plasma bicarbonate levels, along with hyponatremia, hypochloremia, and hypokalemia. The urine output may be reduced with high specific gravity, containing abundant protein, renal epithelial cells, and various casts.
Severe leukopenia, where the white blood cell count falls below 3.0X10^9/L and shows no signs of recovery, suggests a poor prognosis and reduced likelihood of recovery.
On the other hand, a marked leukocytosis, primarily characterized by a significant increase in neutrophils and leftward shift of the nucleus, is known as regenerative left shift. This indicates a strong immune response, robust bone marrow hematopoietic function, and the release of a large number of granulocytes into the peripheral blood. Such a situation suggests that the dog's body is moving towards recovery, and the prognosis is generally favorable.
A normal or slightly elevated white blood cell count reflects a new balance between bone marrow production and tissue demand. This balance is achieved when the bone marrow responds to cytokines (growth factors) released from areas of tissue damage, leading to an increase in neutrophil production.
The absence of a left shift suggests that the bone marrow has met the tissue's demand for increased neutrophils. This also implies a good prognosis for the dog.
