Page 255 - Clinical Hematology Atlas

CHAPTER 24 BODY FLUIDS 239

CRYSTALS SOMETIMES FOUND IN SYNOVIAL FLUID

Cells that may be found in normal synovial fluids include lymphocytes, monocytes, and
synovial cells. Synovial cells, which line the synovial cavity, resemble mesothelial cells (see
Figure 24-19) but are smaller and less numerous. Increased numbers of polymorphonuclear
neutrophils may be seen in bacterial infection and acute inflammation. When neutrophils
are seen, a careful search for bacteria should be performed. Tumor cells are possible but quite
rare. LE cells may also be seen (see Figure 24-18).
It is important to perform a careful evaluation for crystals in synovial fluid. Although it
is not necessary to use a stain, Wright stain is sometimes used. A polarizing microscope with
a red compensator should always be used for confirmation. The most common crystals are
monosodium urate, calcium pyrophosphate, and cholesterol.

B
A

FIGURE 24–30 Monosodium urate crystals
(synovial fluid 31000; Wright stain). Needlelike
crystals with pointed ends may be intracellular
(A), extracellular (B), or both.

Associated with: Gout