Elsevier

Urology

Volume 76, Issue 1, July 2010, Pages 242-245
Urology

Urolithiasis
The Risk of Recurrent Urolithiasis in Children Is Dependent on Urinary Calcium and Citrate

Paper presented at the Annual Meeting, American Urological Association, Orlando, FL, May 2008.
https://doi.org/10.1016/j.urology.2009.09.084Get rights and content

Objectives

To determine which risk factors help predict recurrent stone formation. Urinary stone disease is relatively rare in children. At our institution, a full urinary metabolic evaluation is initiated after the first stone episode.

Methods

A retrospective cohort study was performed to assess urinary metabolic profiles in children with urolithiasis. Twenty-four–hour urine collections were performed and evaluated. Urine chemistries were adjusted for creatinine and weight. Abnormal thresholds were obtained from the available published data. The patients were stratified into solitary or recurrent stone formers by review of the medical record. Multivariate analysis was performed with a logistic regression model to assess for independent risk factors for stone recurrence.

Results

A total of 148 samples from 88 patients with solitary stones and 84 samples from 51 patients with recurrent stones were evaluated. Age and gender were well-matched between the 2 groups. Most known stones were calcium oxalate, and there were no radiolucent stones in those with unknown composition. A significantly higher number of patients with recurrent stones had abnormal values for calcium (73% vs 57%) and citrate (30% vs 13%) by univariate analysis. Both calcium (odds ratio, 2.3, P <.01) and citrate (odds ratio, 3.5, P <.001) remained independent risk factors for stone recurrence by multivariate analysis.

Conclusions

There are significant differences in the urinary calcium and citrate levels between children with solitary and recurrent calcium stone formation. This may allow identification of patients at risk for stone recurrence that may benefit from more aggressive dietary and/or pharmacologic intervention.

Section snippets

Material and Methods

This study analyzes a dataset from a cohort that has been described in a previous publication.5 The data are from a retrospective cohort study that was performed of all children who presented with urolithiasis at a single pediatric institution between 1999 and 2006. Inclusion criteria included patients with a presumed calcium-based renal or ureteral stone based on stone analysis or radiographic imaging and who had at least one 24-hour urinary metabolic evaluation after diagnosis. Exclusion

Results

A total of 148 samples from 88 children with solitary stone formation and 84 samples from 51 children with recurrent stone formation were included in the analysis (Table 1). The mean age of the solitary group was 12.5 years, while that of the recurrent group was 13.1 years. The age range for both groups was 3-18 years. The 2 groups were similar in gender (49% of patients with solitary and 46% of those with recurrent stones were female). Mean follow-up after diagnosis was 3.7 years in the

Comment

The incidence of pediatric urolithiasis is increasing in many western countries including the United States.7, 8, 9 These children can present with severe abdominal and flank pain often leading to hospitalization and occasionally resulting in invasive surgical procedures. Families and patients are thus motivated after this experience to evaluate potential causes for the stone and address any metabolic factors that might predispose them to future episodes of renal colic. A previous family

Conclusions

After the first calcium stone episode, children found to have abnormal values for urinary calcium and citrate are at a significantly higher risk for recurrent nephrolithiasis. Clinicians may thus be able to identify patients for more extensive metabolic evaluation and/or pharmacologic therapy to help decrease recurrent stone formation. A clinical trial to investigate the effects of an intensive prophylactic regimen is needed to assess whether intervention decreases morbidity and improves

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    The wide availability of smart water bottles such as those used in this study would allow patients to operationalize this FP by measuring this additional water volume during the course of their everyday lives. This study differs from previous studies of urine volume among patients with kidney stones, which have largely focused on the inability to maintain high water intake and associated low urine volume.15,18-22 Rather, we estimated the relationship between daily water intake and 24-hour urine volume in order to generate knowledge that helps patients achieve urine output goals to prevent stone recurrence.

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    Interestingly, the mean urinary citrate level was higher in the multiple stone group; however, again, the values for both groups were within the accepted reference ranges. However, as mentioned in prior studies [6,7], interpretations of these results rely heavily on previously established reference ranges of pediatric urinary parameters. Previously published studies of our cohort and other studies support that many urinary parameters change significantly with age [14–16].

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