Elsevier

European Urology

Volume 56, Issue 1, July 2009, Pages 72-80
European Urology

Review – Stone Disease
Diet, Fluid, or Supplements for Secondary Prevention of Nephrolithiasis: A Systematic Review and Meta-Analysis of Randomized Trials

https://doi.org/10.1016/j.eururo.2009.03.031Get rights and content

Abstract

Context

Although numerous trials have evaluated efficacy of diet, fluid, or supplement interventions for secondary prevention of nephrolithiasis, few are included in previous systematic reviews or referenced in recent nephrolithiasis management guidelines.

Objective

To determine efficacy and safety of diet, fluid, or supplement interventions for secondary prevention of nephrolithiasis.

Evidence acquisition

Systematic review and meta-analysis of trials published January 1950 to March 2008. Sources included Medline and bibliographies of retrieved articles. Eligible trials included adults with a history of nephrolithiasis; compared diet, fluids, or supplements with control; compared relevant outcomes between randomized groups (eg, stone recurrence); had ≥3 mo follow-up; and were published in the English language. Data were extracted on participant and trial characteristics, including study methodologic quality.

Evidence synthesis

Eight trials were eligible (n = 1855 participants). Study quality was mixed. In two trials, water intake >2 l/d or fluids to achieve urine output >2.5 l/d reduced stone recurrence (relative risk: 0.39; 95% confidence interval: 0.19–0.80). In one trial, fewer high soft drink consumers assigned to reduced soft drink intake had renal colic than controls (34% vs 41%, p = 0.023). Content and results of multicomponent dietary interventions were heterogeneous; in one trial, fewer participants assigned increased dietary calcium, low animal protein, and low sodium had stone recurrence versus controls (20% vs 38%, p = 0.03), while in another trial, more participants assigned diets that included low animal protein, high fruit and fiber, and low purine had recurrent stones than controls (30% vs 4%, p = 0.004). No trials examined the independent effect of altering dietary calcium, sodium, animal protein, fruit and fiber, purine, oxalate, or potassium. Two trials showed no benefit of supplements over control treatment. Adverse event reporting was poor.

Conclusions

High fluid intake decreased risk of recurrent nephrolithiasis. Reduced soft drink intake lowered risk in patients with high baseline soft drink consumption. Data for other dietary interventions were inconclusive, although limited data suggest possible benefit from dietary calcium.

Introduction

The lifetime prevalence of nephrolithiasis has been estimated at 13% among men and at 7% among women [1], [2], with conflicting data regarding whether prevalence is increasing [1], [2], [3]. Although stones may be asymptomatic, potential consequences include renal colic, urinary tract obstruction, infection, hospitalizations, and procedure-related morbidity. Following an initial stone event, the spontaneous 5-yr recurrence rate is 35–50% [4].

In large observational studies, several modifiable factors have been associated with increased risk of nephrolithiasis, including low fluid intake, low dietary calcium, and low dietary potassium, while results for diets with increased animal protein and increased sodium have been mixed [5], [6]. Although a number of trials have evaluated the efficacy of diet, fluid, or supplement interventions in reducing risk of recurrence, few have been included in previous systematic reviews [7], [8] or have been referenced in recent nephrolithiasis management guidelines [9], [10]. Therefore, we conducted this systematic review and meta-analysis to clarify the evidence on the benefits and the adverse effects of diet, fluids, and supplement treatments for secondary prevention of nephrolithiasis.

Section snippets

Literature search

We searched Medline (January 1950 to March 2008) using the following terms: urolithiasis and (controlled clinical trial or randomized clinical trial or randomized controlled trial or systematic reviews or meta-analysis). Bibliographies of retrieved trials and review articles also were examined.

Selection criteria

A trial was eligible for inclusion if it met the following criteria: (1) it was composed of community-dwelling participants aged ≥18 yr with at least one prior resolved episode of renal colic; (2) it was

Study selection

We identified 579 citations via our Medline search. After review of titles and abstracts, we retrieved 28 articles for detailed review, of which 8 met inclusion criteria. No additional references identified from bibliographies of retrieved trials and review articles met inclusion criteria.

Trial characteristics

Eight trials of diet [13], [14], [15], [16], [17], [18] or supplement interventions [19], [20] met eligibility criteria and were included in this review (1855 total participants; number of participants per

Conclusions

Our systematic review of randomized controlled trials (RCTs) found that high water intake lowered long-term risk of nephrolithiasis recurrence by approximately 60% and that among men with high baseline soft drink intake, reduced soft drink consumption modestly lowered risk of recurrent renal colic. Results from one trial suggested that when added to increased water intake, a diet including higher calcium, lower animal protein, and lower sodium reduced stone risk compared with a low-calcium

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