Association between body mass index and urolithiasis in children

Purpose: The prevalence of obesity and urolithiasis in children has increased with time. We evaluated the relationship between body mass and urolithiasis in children.

Materials and methods: We performed a matched case-control study in a network of 30 primary care pediatric practices. Cases included subjects with ICD-9 codes for urolithiasis and controls were matched on age, duration of observation before the index date and clinical practice. Age and sex specific body mass index z scores at the time of the stone episode were calculated. Continuous body mass index z scores and clinical weight categories were evaluated with covariates, including race, ethnicity, gender and payer status. The OR and 95% CI were calculated using multivariate conditional logistic regression.

Results: We identified 110 cases and 396 matched controls, of whom 1.9% and 4.3% were overweight, and 3.7% and 4.5% were obese, respectively. On multivariate conditional logistic regression analysis the continuous body mass index z score (OR 0.84, 95% CI 0.63-1.12, p = 0.18), overweight status (OR 0.13, 95% CI 0.01-1.18) and obese status (OR 0.18, 95% CI 0.02-1.40) were not associated with urolithiasis. However, black race (OR 0.35, 95% CI 0.15-0.85) and Medicaid payer status (OR 0.47, 95% CI 0.24-0.93) were associated with a significant decrease in the odds of urolithiasis.

Conclusions: High body mass was not associated with urolithiasis in our primary care pediatric practice network. However, black race and Medicaid payer status were associated with decreased odds of urolithiasis.