Uric acid crystals are seen in a variety of shapes, including rhombic, four-sided flat plates (whetstones), wedges, and rosettes.Form in urine when pH < 5.5
They usually appear yellow-brown, but may be colorless and have a six-sided shape, similar to cystine crystals.
Uric acid crystals are highly birefringent under polarized light, which aids in distinguishing them from cystine crystals .
Increased amounts of uric acid crystals, particularly in fresh urine, are associated with increased levels of purines and nucleic acids and are seen in patients with leukemia who are receiving chemotherapy, in patients with Lesch-Nyhan syndrome, and, sometimes, in patients with gout.
urinalysis & body fluids by susan kinstrasinger