Hematology

Pancytopenia is defined as anemia (typically non-regenerative), neutropenia, and thrombocytopenia. The term implies that the bone marrow is responsible for the cytopenias, with very few extramedullary diseases producing this constellation of hematologic abnormalities. Exceptions are severe bacterial sepsis which can result in anemia of inflammatory disease, severe neutropenia with a left shift and toxic change from […]

Changes in total and differential leukocyte count are usually grouped into patterns, which facilitate interpretation. These patterns are: Stress leukogram Physiologic leukocytosis Inflammatory leukogram, including a table on how we use terminology to describe changes in mature (segmented) and immature (bands, metamyelocytes etc) neutrophils and how we use this terminology to understand what is going

Erythrocytosis is defined as an increase in red blood cell (RBC) mass, usually absolute, and is also associated with an increased hematocrit (HCT) and hemoglobin concentration. Although some use the term polycythemia interchangeably with erythrocytosis, the two are not synonymous. Polycythemia in precise terms refers to an increased number of any hematopoietic cell in blood, be it RBCs,

There are many different causes, which can be separated mechanistically as done below. A retrospective study of anemia in 456 dogs (excluding those with acute blood loss anemia) showed that the most frequent causes of anemia were inflammatory disease and cancer-associated anemia (which could be multifactorial in origin and the cohort could have included cases

There are three main mechanisms for anemia: Hemorrhage: This is due to loss of RBCs outside vessels. These anemias are usually regenerative (given sufficient time for a bone marrow response). Hemorrhage can be: Internal: Into a tissue or body cavity, such as the peritoneum. External: In this case, blood (RBC, plasma) is lost from the body,

Changes in red blood cell (RBC) size on a blood smear correspond to changes in diameter of the cell and not necessarily to changes in red blood cell volume, as assessed by the hematologic analyzer. Cells can appear smaller but be of normal volume (e.g. spherocytes) whereas other cells actually appear bigger because they are

Platelet aggregation (clumping) will affect platelet counts. This often results in a falsely decreased count as clumps of platelets will not be counted with any automated hematology analyzers. Similarly, the numbers of platelets cannot be accurately counted manually (with a hemocytometer) in clumped samples (it is impossible to know how many platelets are in a

Platelets tend to very in size in all species, with some large platelets being seen in all species. The variation in platelet volume is measured on hematologic analyzers as the platelet distribution width. This is analogous to the red blood cell distribution width and is calculated similarly (standard deviation of platelet volume ÷ mean platelet

A common and important morphologic abnormality of neutrophils is so-called “toxic change“. Contrary to what has been written in many books, toxic change in neutrophils is not necessarily associated with “toxemia”. The term derives from the fact that these abnormalities were first noticed in human patients with gram negative sepsis and endotoxemia. However, toxic change

The five major categories of leukocytes in mammals are neutrophils, eosinophils, basophils, lymphocytes, and monocytes. The first three collectively are called granulocytes, because they contain granules in their cytoplasm, and the latter two collectively are called mononuclear cells in reference to their round nuclei. These collective terms are somewhat misleading since some granulocytes have barely perceptible granules