Risk of recurrence of idiopathic calcium kidney stones: analysis of data from the literature

BACKGROUND: Nephrolithiasis is a frequent condition. While it is generally accepted that such condition carries a risk of recurrence over time, the exact risk and its predictors have been rarely quantitated. We aimed to estimate recurrence of kidney stones, overall and in specific subgroups, from randomized controlled trials (RCTs) of calcium stone formers. METHODS: Systematic review of RCTs of adult patients with idiopathic calcium kidney stones. Recurrence rates analyzed in subgroups based on type of intervention and other characteristics, using Poisson regression models. RESULTS: The analysis included 21 RCTs with 2168 participants over a median follow-up of 3.2 years (range 0.5-9.7). The median recurrence of kidney stones was 15 per 100 person-years (range 0-110). Recurrence was higher in those with two or more previous stone episodes compared to those with a single episode at enrolment (16 vs. 6 per 100 person-years, p < 0.001) and in those untreated or treated with dietary changes compared to those treated with drugs (26 vs. 23 vs. 9 per 100 person-years, p < 0.001). The effect of drugs on recurrence seemed to be beneficial only among those with two or more previous stone episodes. CONCLUSIONS: The overall recurrence rate of stones depends on factors such as previous stone history and type of treatment. Dietary approaches seem to be more effective among single stone formers, whereas drugs seem to be more effective among recurrent stone formers.