Calcium oxalate nephrolithiasis: an easy way to detect an imbalance between promoting and inhibiting factors.

Calcium oxalate stone formation depends on both urine oversaturation with calcium oxalate--which in turn depends mainly on oxalate excretion--and the excretion of inhibitors; the possibility that a ratio of these variables might differentiate stone-formers from stone-free subjects was explored, 24-h urine samples from 20 control subjects and 53 idiopathic calcium oxalate stone-formers receiving a standard diet were studied. A further group of 2-h urine samples (from 7 to 9 a.m.). collected after a overnight fast from 16 non-stone and 24 stone-forming persons on a normal diet, were also examined. The ratio 'oxalate/citrate X acid mucopolysaccharides; (Ox/Cit X AMPs) seems capable of differentiating more than 80% of stone-formers from non-stone-formers using both 24- and 2-h urine collection.