BACKGROUND: The ''stone clinic effect'' refers to the effect of encouraging a high intake of fluid and diet counseling in the clinical evolution of kidney stone disease. Objective: Our objective was to determine the extent of this variable in patients with nephrolithiasis. METHODS: Twenty-five patients (11 female and 14 male; 47.64±10.55 years old) with recurrent nephrolithiasis were prospectively followed for one year, with 3-month interval medical evaluation. Patients were advised to increase the fluid intake, and to limit the intake of salt and protein. No patient was submitted to pharmacological therapy. Two 24-hour urine samples were collected at baseline (S1) and in the end of follow-up (S2) for the measurement of creatinine, calcium, sodium, uric acid, citrate, oxalate and magnesium. Metabolic and radiological activity was also assessed. Urinary calcium oxalate supersaturation (SS) was calculated by Tiselius index. RESULTS: Eleven (44%) patients had hypocitraturia, 9 (36%) hypercalciuria and 5 (20%) hyperuricosuria. Urinary volume increased (1903±811 vs. 2381±919 ml/day, p<0.05) and SS decreased significantly (1.13±0.8 vs. 0.6±0.2, p<0.01). During follow-up, the number of stones decreased when compared to baseline (S1=2.04±1.51 vs. S2= 0.72±0.23 stones, p<0.001). There was no evidence of new stone formation or growth in 20 of 25 patients (80%). CONCLUSIONS: The ''stone clinic effect'' significantly decreased urinary SS for calcium oxalate and the formation of new kidney stones in 80% of patients during first year of follow-up.
Nephrolithiasis; Renal stone; Metabolic alterations; Calcium
