Stone Risk in Pediatric Obese Patients, A Dietary Phenomenon
Pankaj P. Dangle, MD,MCh1, Kyle Wood, MD2, Ross Holmes, PhD2, David Kitchens, MD1, Dean Assimos, MD1, David Joseph, MD1.
1Children's Of Alabama, Birmigham, AL, USA, 2University of Alabama at Birmingham, Birmigham, AL, USA.
BACKGROUND: Unlike adults, association between obesity and pediatric stone disease is unclear. Literature supports a geographic variation in a number of differences in the 24 hour urinary parameters. Our objective was to characterize the 24 hour urinary parameters in our geographic area.
METHODS: We retrospectively reviewed our pediatric stone database of 266 patients and identified 262 non cystinuric patients who had 24 hour urine studies with available data on age, sex, and BMI. Patients were grouped based on BMI; BMI percentile <85th (normal, gp 1) and ≥85th as obese and overweight (Ob/Ow) (gp 2). Statistical methods included student t-test, Welch's t-test, and Pearson correlation.
RESULTS: Of 262 pts, 157 (60%) were female and 105 (40%) were males. 12(7.6%) males were Ob/Ow and 13 (12.4%) females were Ob/Ow. For all stone formers (SFs), 24 hour uric acid (p-0.015), Na (p-0.035), phosphate (p-0.05), UUN (p-0.027), Cr (p-0.005), and sulfate excretion (p-0.05) were higher in gp2 compared to gp1. On sub analysis by gender, females had significantly higher UA (p-0.016), Na (0.05), phosphate (p-0.003), sulfate (0.003), UUN (0.008) and creatinine (0.001) in gp2 versus gp1. In males, creatinine (0.004), phosphate (0.008) and Mag (0.013) were higher in gp2 compared to gp1. Increasing BMI correlated with higher urinary oxalate excretion in females (r=0.185, p-0.02), but not males (r0.47,p-0.63). In females, 9% were Hox (>40mg/dl) compared to males 20%. Hypercalciuria (>250mg/dl) were similar in in both genders (9% in females and 9.5% in males). CONCLUSIONS: Significant differences exist in the 24 hour urinary parameters in Ob/Ow pediatric pts compared to normal. These may be reflective of dietary habits associated with obesity. The significant positive correlation between BMI and oxalate excretion in females is similar to what has been reported in adults.
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