Renal excretion of hydrogen ions in stone formers

Urinary hydrogen ion excretion has been studied in 68 adult stone formers and in 50 controls. Under basal state, the stone formers showed statistically significant higher urinary pH, and lower 24-hour urinary titrable acid, ammonium and total hydrogen. On the 3rd day of ammonium chloride loading test, the stone formers showed statistically significant higher urinary pH and lower 24-hour urinary titrable acid, ammonium, total hydrogen and plasma bicarbonate. 'Clearance' indices of hydrogen ion excretion were also depressed in a great majority of the stone formers. The results indicate the frequent co-existence of defective urinary acidification with nephrolithiasis.