Body fluids

Published on 04/03/2015 by admin

Filed under Hematology, Oncology and Palliative Medicine

Last modified 04/03/2015

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24 Body fluids

Fluid in the cavities that surround organs may serve as a lubricant or shock absorber, provide circulation of nutrients, or function for collection of waste. Evaluation of body fluids may include total volume, gross appearance, total cell count, differential cell count, identification of crystals, biochemical analysis, microbiological examination, immunological studies, and cytological examination. The most common body fluid specimens received in the laboratory are cerebrospinal fluid (CSF); pleural, peritoneal, and pericardial fluids (together known as serous fluids); and synovial fluids. Under normal circumstances, the only fluid that is present in an amount large enough to sample is CSF. Therefore, when other fluids are present in detectable amounts, disease is suspected.

This atlas addresses primarily the elements of fluids that are observable through a microscope. For a more detailed explanation of body fluids, consult a hematology or urinalysis textbook that includes a discussion of body fluids, such as Hematology: Clinical Principles and Applications* or Fundamentals of Urine and Body Fluid Analysis.^†

Because the number of cells in fluids is often very small, a concentrated specimen is preferable for performing the morphological examination. Preparation of slides using a cytocentrifuge is the method commonly used. This centrifuge spins at a low rate of speed to minimize distortion of cells, concentrating the cells into a “button” on a small area of the glass slide. The three elements of the cytocentrifuge are a cytofunnel, filter paper to absorb excess fluid, and a glass slide. These elements are clipped together in a clip assembly, and the entire apparatus is then centrifuged slowly. Excess fluid is absorbed by the filter paper, leaving a monolayer of cells in a small button on the slide. When the cytospin slide is removed from the centrifuge, it should be dry. If the cell button is still wet, the centrifugation time may need to be extended.

When preparing cytocentrifuge slides, a consistent amount of fluid should be used to generate a consistent yield of cells. Usually two to six drops of fluid are used depending on the nucleated cell count. Five drops of fluid will generally yield enough cells to perform a 100-cell differential if the nucleated cell count is at least 3/mm³. For very high counts, a dilution with normal saline may be made. The area of the slide where the cell button will be deposited should be marked with a wax pencil in case the number of cells recovered is small and difficult to locate (Figure 24-1). Alternatively, specially marked slides can be used.

FIGURE 24–1A Wright-stained cytocentrifuge slide demonstrating a concentrated button of cells within the marked circle.

FIGURE 24–1B Wright-stained cytocentrifuge slide from a cerebrospinal fluid containing few cells, demonstrating the importance of marking the cell concentration area.

There may be some distortion of cells as a result of centrifugation or when cell counts are high. Dilutions with normal saline should be made before centrifugation to minimize distortion when nucleated cell counts are high. When the red blood cell (RBC) count is extremely high (more than 1 million), the slide should be made in the same manner as the peripheral blood smear slide (see Chapter 1). However, the examination of the smear should be performed at the end of the slide rather than the battlement pattern used for blood smears. This is because the larger, and usually more significant, cells are likely to be pushed to the end of the slide.

When examining the cytospin slide, the entire cell button should be scanned under the 10× objective to search for the presence of tumor cells. The 50× or 100× oil immersion lens should be used to differentiate the white blood cells. For the performance of the differential, any area of the cell button may be used, but if the cell count is low, a systematic pattern starting at one end of the side of the button and working toward the other is recommended.

Any cell that is seen in the peripheral blood may be found in a body fluid in addition to cells specific to that fluid (e.g., mesothelial cells, macrophages, tumor cells). However, the cells look somewhat different than in peripheral blood, and some in vitro degeneration is normal. The presence of organisms, such as yeast and bacteria, should also be noted (see Figures 24-12 to 24-14).

Cells sometimes found in cerebrospinal fluid

FIGURE 24–5 Reactive lymphocytes (CSF ×1000).

Reactive lymphocytes (Figure 24-5) are associated with viral meningitis and other antigenic stimulation. The cells will vary in size; nuclear shape may be irregular and cytoplasm may be scant to abundant with pale to intense staining characteristics. (See description of reactive lymphocytes, Figure 14-7.)