Effects of a 'common sense diet' on urinary composition and supersaturation in patients with idiopathic calcium urolithiasis.

OBJECTIVES

To test whether dietary advice as the only treatment is able to reduce urinary supersaturation in patients with idiopathic calcium urolithiasis.

METHODS

By means of EQUIL 2, we calculated relative supersaturations of calcium oxalate (RS(CaOx)), brushite (RS(Brushite)), apatite (RS(Apatite)) and uric acid (RS(UA)) of 24-hour urine samples of 68 healthy male controls as well as of 47 male idiopathic calcium stone formers (ICSF) before and after individualized dietary advice (DA). Main goals of DA were (1) to keep urine volume > 2,000 ml/day, and (2) to reduce meat protein intake to 1 g/kg body weight per day. Compliance was judged from changes in urine volume and U(Urea)xV.

RESULTS

In the whole group of ICSF, DA did not alter supersaturations. Only in those 9 ICSF (19%) with good compliance (increase in volume and decrease in U(Urea)xV), RS(CaOx) and RS(UA) fell by 26 and 49%, respectively. Besides poor compliance, these findings can be explained by positive correlations between changes in volume and U(Urea)xV in ICSF (r = 0. 319, p = 0.037) or U(Na)xV (r = 0.342, p = 0.019). For instance, ICSF with volumes >/= 2,000 ml/day had evidence of elevated protein and salt intake; thus, DA mainly focused on protein and salt intake, but not on volume. This resulted in decreases in U(Urea)xV and U(Na)xV, but also in volume; thus, RS(CaOx) remained unaltered.

CONCLUSIONS

DA is able to significantly lower RS(CaOx); however, because intakes of fluid and protein are directly and positively linked to each other, this only can be achieved if high fluid and lower meat protein intake are equally stressed in all ICSF.