Crystallization Properties in Urine from Calcium Oxalate Stone Formers

Abstract

Purpose We determine whether stone formers and normal subjects can be distinguished in terms of supersaturation with calcium oxalate, and inhibition of calcium oxalate growth and aggregation. Materials and Methods An estimate of the ion activity product of calcium oxalate was obtained from the analysis of calcium, oxalate, citrate and magnesium in 16-hour urine samples obtained between 6 a.m. and 10 p.m. The inhibition of calcium oxalate crystal growth and aggregation was assessed in 8-hour urine specimens obtained between 10 p.m. and 6 a.m. Results The ion activity product of calcium oxalate was higher and inhibition of crystal aggregation was lower in stone formers than in normal subjects. Inhibition of crystal growth was lower only in male stone formers. Quotient 1 (10 2 × ion activity product of calcium oxalate/inhibition of crystal growth), quotient 2 (10 2 × ion activity product of calcium oxalate/inhibition of crystal aggregation) and quotient 3 (10 4 × ion activity product of calcium oxalate/[inhibition of crystal growth × inhibition of crystal aggregation]) were significantly higher in stone formers. Conclusions The biochemical risk situation in calcium oxalate stone formers can be summarized by quotient 2 or 3.