Uric acid crystals cannot be demonstrated after fixation in an aqueous fixative.

• A. True
• B. False
• C. Not enough information
• D. Sometimes

Answer: (A)

Uric acid crystals are soluble in water, so fixation in an aqueous fixative dissolves them. Because these fixatives contain water, the crystals disappear during fixation and subsequent processing, making them undetectable with polarized light. To visualize them, use a non-aqueous fixation method (such as absolute alcohol) or examine fresh-frozen tissue where no aqueous fixation has dissolved the crystals. Under polarized light, monosodium urate crystals appear as needle-shaped, birefringent structures, so dissolution by aqueous fixatives explains why they cannot be demonstrated after such fixation.