Hematology and Cytology of Small Mammals

Chapter 36 Hematology and Cytology of Small Mammals

This chapter provides photomicrographs and other information that may be useful during the examination of blood smears and tissue aspirates from selected small mammals. More comprehensive discussions are available elsewhere regarding the evaluation of blood smears from many of these species; these texts are listed among the references.* While knowledge of the plausible differential diagnoses is often critical in the interpretation of cytologic findings, the same general principles of cytology used in dogs and cats can be applied to small mammals. The reference list below includes several excellent veterinary cytology references.

Some of the conditions described here can be accurately diagnosed in house without the delay and expense involved in using a commercial laboratory. Wright’s-Giemsa (modified Romanowsky), new methylene blue, and acid-fast stains were used on the specimens in these photomicrographs. Diff-Quik-type processing or other forms of three-step quick stains, while acceptable for the evaluation of up to several specimens per day, is considered less favorable for use in a busier in-house laboratory for the following reasons: (1) if a large number of slides are to be processed daily, Diff-Quik-type stains are expensive and labor-intensive; (2) jars containing Diff-Quik stains can easily be contaminated with bacteria and fungal elements, particularly when slides containing material from skin, otic, or fecal samples are processed; (3) in many nonneoplastic tissue cells, Diff-Quik staining may create nuclear textures that inaccurately indicate immature changes; (4) polychromasia of red blood cells (RBCs), an important manifestation of erythroid regeneration, is generally not evaluable on Diff-Quik-stained blood smears; and (5) these stains produce variable staining of mast cell granules, occasionally rendering them invisible.

Most of the photomicrographs in this chapter were taken under immersion oil by using a 100× objective and 10× eyepiece, equaling 1000× magnification. For some lesions, evaluation of cytologic specimens can readily be performed by using the microscope’s 40× objective (high dry, 400× magnification). In fact, this lens can be more useful than the 100× lens because it provides a larger field of view, allowing the examiner to evaluate a larger portion of the slide in less time while revealing compelling cellular details and other features. Nonetheless, many clinicians and technicians are not satisfied with the quality of the resolution of this lens. In defense of the 40× objective, optically it is designed to be used principally with slides that have been cover-slipped. A good technique for temporary placement of a cover slip is to deposit a very small drop of immersion oil on the stained smear and then place a rectangular glass cover slip on the drop of oil. If resolution is then not improved upon examination of cover-slipped material, suspect that the lens may have been inadvertently soiled with immersion oil during previous use. A thorough cleaning of the external surface of the lens can be successful, using several cotton swabs thickly moistened with lens cleaner, followed by extended buffing with several dry cotton swabs. On microscopes used by numerous operators, and particularly those where the 100× (oil-immersion) lens receives heavy use, the 40× lens may require frequent cleaning.

Sep 6, 2016 | Posted by in SUGERY, ORTHOPEDICS & ANESTHESIA | Comments Off on Hematology and Cytology of Small Mammals

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