1988 Volume 79 Issue 10 Pages 1646-1652
A method was described for an estimation of the metastable limit of calcium oxalate crystallization in whole human urine. Spontaneous nucleation of calcium oxalate crystals was assessed by titrating 225μl of the urine with increasing quantities of sodium oxalate (1-15mM/L, 25μl) to determine its practical metastable limit using an aggregometer.
The results were as follows:
1) The minimum amount of oxalate necessary to induce nucleation of calcium oxalate was detectable by the turbidity of the aggregometer. The limit of metastability of calcium oxalate in the urine by this method gave fairly good agreement with a method of using a Coulter counter.
2) The measured metastable limit of each sample of urine was inversely proportional to the concentration of urinary calcium, total concentration product of calcium and oxalate in the urine and calcium oxalate ion activity product index.
3) The metastable limit of calcium oxalate in calcium stone formers has a tendency to show a low value comparing with that in healthy controls.
4) Treatment of rice-bran or citrate was able to improve the metastable limit of calcium oxalate in whole urine.
5) It was suggested that the determination of metastable limit using an aggregometer was useful and convenient for evaluating the propensity of calcium oxalate crystallization in the urine and the efficacy of prophylactic treatment of calcium stone.
