Gender differences in seasonal variation of urine stone risk factors.

Abstract

We determined whether men and women differ in urine stone risk factors during the 4 seasons of the year. Measurements from 28,498, 24-hour urines from stone forming patients prior to treatment were analyzed to determine whether monthly variation was significant and whether the sexes differed using ANOVA. Locations of supersaturation maxima were determined. The 2 sexes showed modest sodium depletion in summer with a corresponding decrease in urine calcium but men showed a remarkable decrease in urine volume, causing high calcium oxalate supersaturation. Women had maximum calcium oxalate supersaturation in early winter because of decreasing urine volume and increasing urine calcium excretion. Urine pH was reduced in the 2 sexes during summer but the decrease was far more marked in men, who had a uric acid supersaturation spike. Overall the sexes differ markedly in the timing of stone risk. Men show a dual summer calcium oxalate and uric acid high risk, while women show a high early winter calcium oxalate high risk.