Monosodium Urate Monohydrate as Spherulites

Abstract

The demonstration of urate crystals in synovial fluid and within synovial leukocytes is recognized as the most definitive criterion for the diagnosis of gout (1). The characteristic crystals have been described by scientists from Van Leeuwenhoek in the 1600’s to the present as being “needle-like” in shape. These crystals have been further described by their anisotropic quality of birefringence detectable by using the polarizing microscope. Addition of a first order red quartz conpensator to the optic system helps identify monosodium urate monohydrate (MSUM) by its ability to alter the light’s wavelength and change the transmitted color from red to yellow in the gamma plane of the compensator (2). MSUM is thus, by definition, negatively birefringent. Crystals which are blue when parallel to the gamma plane are defined as positively birefringent.