Risk Factors in Urinary Calcium Oxalate Stone Formation and their Relation to Urinary Calcium Oxalate Supersaturation

BACKGROUND: We studied the effect of potential risk factors of urinary calcium oxalate saturation on calcium oxalate stone formation. METHODS: Using the Equil2 program, the DG values of calcium oxalate in 390 clinical urine specimens were estimated in 5 healthy male individuals with and without citrate therapy. RESULTS: Critical calcium-oxalate supersaturation (DG value, > 2.8) was noted in 15 out of 390 urine specimens. Of the 15, 14 late night or morning specimens had critical calcium oxalate supersaturation, while only 1 afternoon specimen was supersaturated. Critical calcium oxalate supersaturation was often associated with hyperoxaluria and hypercalciuria, while undersaturation was often associated with hypomagnesiuria, a high Ca/Mg ratio, and hypocitraturia. CONCLUSIONS: Hypomagnesiuria, hypocitraturia, and a high Ca/Mg ratio appear to be poor indicators of calcium-oxalate supersaturation, and it is hard to predict the level of calcium-oxalate saturation using single parameters.