URINARY SODIUM TO POTASSIUM RATIO AND URINARY STONE DISEASE

The relation was investigated of urinary sodium to potassium ratio in first morning voided urine (spot urine) to urinary stone disease in 3, 625 men and women aged 25 to 74 years participating in the baseline ex amination of the Gubbio Population Study. History of urinary stone dis ease (excre tion of stone, and/or radiographic or ultrasonic evidence of urinary stone, and/or operation for urinary stone removal) was repo rted by 127 individ uals (3.50%). Prevalence of urinary stone disease was lower in women than in men (2.59 and 4.58%, P < 0.001) and positiv ely related to age (P < 0.001). Compared to nonstone formers, stone fo rmers (N = 127) had higher urinary sodium to potassium ratio (P < 0.01 ), with similar plasma potassium and sodium concentration. In both sex es, urinary stone disease was positively related (P < 0.001) to sodium to potassium ratio: quartile analysis of this ratio showed that preva lence of stone formers in quartile 4 compared to quartile 1 was 3.33 t imes higher in women (P < 0.005, 95% confidence interval 1.36/8.60) an d 2.71 times higher in men (P < 0.004, 95% confidence interval 1.35/5. 93). In multiple logistic regression, urinary stone disease was signif icantly related to age, sex, and urinary sodium to potassium ratio (P < 0.01), controlled for other possible confounders, with or without ex clusion of stone formers with plasma creatinine >1.20 mg/dl. In an alt ernative model, with urinary sodium to potassium ratio not included, u rinary stone disease was positively related to urinary sodium to creat inine ratio (P < 0.001) and weakly (P = 0.079) related inversely to ur inary potassium to creatinine ratio. The data indicate that high sodiu m to potassium ratio in the urine is related to urinary stone disease.