Body fat composition and occurrence of kidney stones in hypercalciuric children

In the last 10 years, the incidence of kidney stones has increased in the pediatric population, and this rise has been paralleled by a significant increase in pediatric obesity rates in the USA. The purpose of this study was to evaluate percentage body fat (%BF) measured by dual energy X-ray absorptiometry (DXA) in hypercalciuric children with and without kidney stones. A retrospective chart review was performed on children with idiopathic hypercalciuria based on a 24-h urine calcium excretion of >4 mg/kg/day or >200 mg/day who had undergone DXA scanning. Patients were then classified by sex and by %BF (3 categories; normal: <27% girls, <21% boys; at risk for obesity: 27-36% girls, 21-30% boys; obese: >36% girls, >30% boys). The 2003-2004 NHANES data were used as a control. Fifty patients (24 males) were analyzed, of whom 26% were assessed as having a normal %BF, 44% as being at risk for obesity, and 30% as being obese. Children with an increased %BF had a significantly higher occurrence of kidney stones (p = 0.03) than those with a normal %BF. No significant differences were noted in 24-h urine chemistries between the groups. In conclusion, an increased %BF was associated with an increased occurrence of kidney stones in children with idiopathic hypercalciuria.