PHOSPHATES PRECIPITATING FROM ARTIFICIAL URINE AND FINE-STRUCTURE OF PHOSPHATE RENAL CALCULI

Phosphates precipitating from artificial urine in the pH range 6-8 wer e identified using X-ray diffraction, chemical analysis and scanning e lectron microscopy. The influence of magnesium and citrate on phases p recipitating from urine was established. From urine containing a norma l quantity of magnesium (around 70 ppm), brushite accompanied by hydro xyapatite (HAP) precipitated at pH less than or equal to 7.0 and struv ite with HAP at pH > 7.0. HAP was formed exclusively from magnesium de ficient urine at pH 7.0. Newberyite, octacalcium phosphate and whitloc kite were not identified. The chemical and phase composition and inner fine structure of 14 phosphate calculi were studied. Three types of s tones were distinguished based on their magnesium content: (I) stones rich in magnesium composed of struvite, hydroxyapatite and abundant or ganic matter, (ii) stones with low magnesium content constituted by ca lcium deficient hydroxyapatite, up to 5% of struvite, considerable amo unt of organic matter and occasionally brushite, and (iii) calculi wit hout magnesium consisting of brushite, hydroxyapatite and little organ ic matter. Conditions prevaling during stone-formation assessed for ea ch type of stone were confirmed by corresponding urinary biochemical d ata and corroborate the in vitro studies of phosphates precipitation.