Spherical calcium bodies in stone-forming urine

Twenty-four hour urine specimens from 26 active stone formers and 15 non-stone formers were passed through an ultrafilter that retained all molecules with a molecular weight greater than 50,000. Microscopic spherical bodies that laked alizarin red were observed in the urinary ultrafiltrate from 24 of 26 active stone formers. Only three of 15 non-stone-forming control urines contained these bodies. Histochemical studies showed the presence of calcium, phosphorus, and carbohydrate-protein complexes. No crystalline elements were detected.