Dr. William DeFoor, et al., retrospectively reviewed all children who presented with urolithiasis at a single pediatric institution between 1999 and 2006. They wanted to determine which children were at greatest risk for recurrent stone formation. Their inclusion criteria were presumed calcium based renal ureteral stone, based on stone analysis of radiographic imaging with at least one 24-hour urinary metabolic evaluation conducted after initial diagnosis. Stones were sent for analysis and subjects were given a prescription for a urinary metabolic evaluation to be performed at home. Urine chemical analyses such as calcium, citrate, uric acid and oxalate were adjusted for urine creatinine and by weight. The patients were stratified into 2 groups of solitary and recurrent stone formers based on the review of their medical records. The reviewers were blinded regarding the results of the metabolic evaluation.

The group found that they had a total of 148 samples from 88 solitary stone formers and 84 samples from 51 recurrent stone formers. The mean age was 12.5 years in the solitary stone formers and 13.1 years in the recurrent stone formers. There were no differences in gender proportions. The mean follow up was 3.7 years and 3 years for solitary and recurrent stone formers respectively. Timed urinary calcium levels referenced to creatinine and citrate were significantly higher in patients with recurrent stones. Super saturation levels of calcium oxalate were higher in recurrent stone formers, but it did not reach statistical significance. In this patient cohort, calcium indices were significant ly higher in the recurrent stone formers, especially when referenced to citrate. Despite the differences that the group found in calcium excretion, the group majority of patients in both groups were still within the currently accepted normal reference range of less than 4 mg per kilogram per day.

The group concluded that their work showed a significant difference in the 24-hour urinary calcium levels between solitary and recurrent calcium stone forming children. Timed urinary calcium levels referenced to creatinine and citrate were significantly higher in those patients with recurrent stones. They felt that a patient with increased urinary calcium indices in the 24-hour specimen might benefit from a more aggressive initial dietary and pharmacologic regimen.

Defoor W, Minevich E, Jackson E, Reddy P, Clark C, Sheldon C, Asplin J.
J Urol. 2008 Apr 22;179(6):2369-2372.

Writtten by UroToday Medical Editor Pasquale Casale, MD

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