[Exaggerated calciuric response to an acute acid load in patients forming renal calcium stones]

Calciuric response to an acute acid load was studied in 13 recurrent calcium stone formers and in 9 control subjects. The evolution of calcium and citrate urinary excretion related to creatinine, of plasma acid base status, of urinary pH, of acid excretion was analysed before and after NH4Cl administration (2 mmol/Kg). Fasting calciuria (expressed as Ca/Cr) was identical in the 2 groups, however the urinary calcium excretion after the acid load was greater in the stone formers group than in the controls (0.378 +/- 0.113 vs 0.253 +/- 0.108 mg/mg). The increase in acid excretion and the decrease in urinary citrate excretion were identical in the 2 groups.