A prospective study of nonmedical prophylaxis after a first kidney stone

To assess, in a multicentre prospective randomized study, the effectiveness of specific nonmedical prophylaxis and nonspecific dietary prophylaxis in patients treated after experiencing their first idiopathic calcium-containing kidney stone.

From 1991 to 1994, 242 patients with idiopathic calcium urinary stones from three urological centres were randomly assigned into two groups. In group 1 (intervention, 113 patients), a specific dietary regimen was recommended and thereafter corrected according to a comprehensive metabolic evaluation. Group 2 (control, 94 patients) underwent only minimal metabolic screening and used general dietary measures, with no regular follow-up. An increased fluid intake was recommended in both groups. After 3 years, the effectiveness of the prophylactic and dietary regimens was evaluated in 207 patients.

At entry, the clinical characteristics were comparable in the two groups, with only extracorporeal lithotripsy being more frequent in group 2. Almost 80% of patients reported a high intake of meat and a low intake of dairy products. In group 1 and 2, a recurrent stone was encountered in seven (6%) and 18 (19%) patients, respectively; recurrent and growing stones were found in eight (8%) and 22 (23%) patients, respectively (P<0. 01). There was a higher incidence of bilateral residual (or untreated) stones, and Weddellite stones (P<0.001) among patients with a recurrent or growing stone. An analysis of the dynamics of the metabolic variables indicated the significance of repeated dietary counselling.

Specific dietary therapy, adjusted according to a metabolic evaluation, is more effective than nonspecific general dietary recommendations in preventing the formation of a second urinary stone.