Ureteropelvic junction obstruction and coexisting renal calculi in children: role of metabolic abnormalities

Objectives. To identify the role of metabolic risk factors in the development of renal calculi associated with ureteropelvic junction obstruction (UPJO) in children. Methods. A metabolic evaluation, including serum biochemistry and measurement of daily urinary calcium, creatinine, oxalate, citrate, magnesium, urate, and inorganic phosphorus, was carried out in three different populations as follows: UPJO group, 12 children with UPJO and coexisting nephrolithiasis (median age 6 years); calcium stone formation (CSF) group, 90 children with normal urologic anatomy and calcium urolithiasis (median age 7 years); control group, 24 healthy children (median age 7.3 years). The investigation data of the three groups were compared. Results. The stone composition was calcium oxalate in 9 of the 12 children with UPJO. The investigation data of the UPJO group and CSF group were not significantly different. Both groups differed from the control group in a similar manner. The UPJO and CSF groups excreted more oxalate ( P = 0.067 and 0.014, respectively) and less citrate ( P = 0.020 and 0.010, respectively) than did the control subjects. Conclusions. Abnormal urinary biochemistry seems to have an additional role in the high incidence of nephrolithiasis in children with upper tract anatomic anomalies, and the urinary biochemistry should be screened in such children.