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What is cytology and how is it used on my pet?
- Cytology is the retrieval of cells, fluid, blood, pus, and urine for microscopic
evaluation. Once the biopsy has been taken, the cells are stained with special stains
examining the population of cells, bacteria, or yeast.
- In the case of solid masses, a very small gauge needle is attached to a large syringe.
The needle is inserted into the mass and the cells are actually aspirated of "sucked" into
the shaft of the needle. If the bottom of the syringe fills with blood or fluids, the biopsy
is contaminated and harder to evaluate. The best fine needle aspirate is when only a small
number of representative cells are retrieved. These cells, then, are spread out onto a glass
slide and stained. The goal, in any cytological prep, is to have a single layer of cells to
examine, without contamination. The morphology, or how the cells look, is evaluated. For
example, cells derived from glandular tissues have a round or boxy "look," and cells from
connective tissue (scar tissue, tendons, ligaments, fascia, and bone) have a slender,
spindle-shaped look. Then the nucleus (the brains of the cell) is evaluated. In some cases,
determining whether a cell or group of cells is malignant or benign can be gained by
examining the nucleus. Malignant nuclei often show the chromosomes dividing or there may be
more than one nucleoli in the nucleus.
- In the case of bodily fluids, such as urine and cavity fluids, the fluid is first
centrifuged at a high rate of speed to separate the fluid from the cells. The "pellet" is
then spread out onto a slide and stained. In this instance, we are often looking for
organisms (bacteria and yeast - fungi), inflammatory cells, and cancer cells. If bacteria
are found, information as to the kind of antibiotic to use can be derived. And in the case of
yeast, as in ear discharge, we can better determine which medications are best to use.
- Lastly, a direct cytology of feces in clinical cases of diarrhea can be very important. A
lot of information can be gleaned from this prep. Are there an overwhelming number of
bacteria indicating an "overgrowth of bacteria in the small bowel?" Are there microscopic
parasites, such as Giardia, that may be producing the diarrhea? Is there a large number of
blood cells noted likely indicating a possible GI hemorrhage or bout of colitis?
Our in-house cytology lab is a big part of how we practice medicine. Thirty years of looking
at slides has been very helpful in determining whether that mass should be removed or left
alone; cytological preps can help sort out reasons for anemia, accumulation of cavity fluids,
or solving the dilemma of the patient that is now having accidents in the house. In the end,
however, we can always send off the slides to a "boarded" pathologist for review and second
opinion.
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