Calcium oxalate crystalluria.

Calcium oxalate crystals were obtained from urine specimens submitted to a hospital laboratory. The incidence of crystalluria was 4.2 per cent of 42 times the maximum reported incidence of urinary calculi. In our opinion the crystalluria was real and not artifactual. The crystalline structure was determined by polarized light, x-ray diffraction and electron microprobe analysis. Calcium oxalate occurs in several forms--the dihydrate as bipyramidal and dodecahedral prisms, the monohydrate as biconcave ovals, dumbbell shapes and intermediate forms.