Urinary sodium excretion in renal stone formers. An epidemiological study

In the present investigation 238 randomly selected male individuals of the general population (age 19--41 years) and 42 age-matched male patients with recurrent renal stone formation (calcium oxalate and/or calcium phosphate) were studied under outpatient conditions without dietary restrictions. Urinary Na excretion was 207 +/- 82 mmol/24 h (range 55--570) in controls and 208 +/- 100 (range 76--575) in recurrent renal stone formers. Both in controls (r = 0.36; p less than 0.01) and in stone formers (r = 0.4; p less than 0.01) a significant correlation was observed between urinary excretion of sodium and calcium. Urinary sodium excretion was unrelated to systolic or diastolic blood pressure in normotensive or hypertensive individuals. This finding indicates that factors other than sodium are involved in the maintenance of hypertension. Urinary sodium, presumably an index of intake of nutrients, was significantly correlated to several coronary risk factors, e.g. fasting glucose, cholesterol and overweight. There existed a significant inverse relationship between fasting plasma phosphate and urinary sodium, but not between fasting plasma phosphate and serum iPTH or urinary cAMP. This finding points to some function of sodium excretion as one determinant of plasma phosphate.