Influence of body mass index on quantitative 24-hour urine chemistry studies in children with nephrolithiasis
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Published on: February 9, 2021
Brian H Eisner1, Michael L Eisenberg, Marshall L Stoller
1Department of Urology, University of California-San Francisco, California 94143, USA. eisnerbh@urology.ucsf.edu
Insights
High body mass index in children is linked to lower urine oxalate and higher calcium phosphate saturation, increasing kidney stone risk. Pediatricians should consider these factors in evaluating pediatric nephrolithiasis.
Area of Science:
- Pediatric Nephrology
- Urology
- Obesity Medicine
Background:
- Adult obesity is a known risk factor for nephrolithiasis.
- The relationship between pediatric obesity and nephrolithiasis risk is not well understood.
- This study investigates the association between body mass index (BMI) and urine chemistry in children with kidney stones.
Purpose of the Study:
- To examine the association between body mass index (BMI) and 24-hour urine chemistry in children with a history of nephrolithiasis.
- To identify specific urine chemistry parameters affected by BMI in pediatric patients.
- To provide insights into the mechanisms linking obesity to kidney stone formation in children.
Main Methods:
- Retrospective review of 24-hour urine chemistry studies from 43 children with a history of nephrolithiasis.
- Calculation and stratification of body mass index (BMI) by percentile.
- Multivariate analysis of urine chemistry parameters adjusted for creatinine excretion and age.
Main Results:
- Body mass index (BMI) percentile varied among the study cohort.
- Increased BMI was significantly associated with decreased urine oxalate excretion.
- Increased BMI showed a significant positive association with supersaturation of calcium phosphate.
Conclusions:
- Elevated body mass index (BMI) in children with nephrolithiasis is linked to reduced urine oxalate and increased calcium phosphate supersaturation.
- These findings highlight the clinical implications of pediatric obesity in kidney stone disease.
- Healthcare providers should consider BMI when evaluating children presenting with kidney stones.
Purpose:
A high body mass index increases the risk of nephrolithiasis in adults. Despite the growing problem of pediatric obesity, little is known about the relationship between body mass index and risk of nephrolithiasis in children. We examined the association between body mass index and 24-hour urine chemistry studies in children with a history of nephrolithiasis.
Materials And Methods:
A total of 43 children were included in the study. We retrospectively reviewed a database of 24-hour urine chemistry studies. We calculated body mass index for each individual and cases were then stratified by percentile. The 24-hour urine chemistry studies were adjusted for daily creatinine excretion, urine volume was adjusted for age, and pH and urine supersaturations were unadjusted.
Results:
Body mass index percentile was below the 25th percentile in 8 cases, 25th to 49th percentile in 7, 50th to 74th percentile in 5 and 75th percentile or above in 14. On multivariate analysis the only 24-hour urine parameters with a significant relationship to body mass index were urine oxalate (negative relationship) and supersaturation of calcium phosphate (positive). As body mass index increased, urine oxalate excretion decreased and supersaturation of calcium phosphate increased.
Conclusions:
A high body mass index is associated with decreased urine oxalate and increased supersaturation of calcium phosphate. Given the increasing prevalence of obesity in younger patients, our findings have important clinical implications. Pediatricians and pediatric subspecialists should be aware of these findings when evaluating children with nephrolithiasis.
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