A Calcium to Citrate Ratio will Distinguish Solitary and Recurrent Stone-Forming Children

The prevalence of urinary stone disease is increasing in children. We have previously reported a high rate of urinary metabolic abnormalities in stone-forming children including hypercalciuria and hypocitraturia. The purpose of this study is to determine if a calcium to citrate ratio can help predict those at risk for recurrent stone formation.

A retrospective cohort study was performed to assess calcium to citrate ratios in children with urolithiasis. Two 24-hour urine collections were performed. The urinary excretions of calcium and citrate were analyzed, and the calcium to citrate ratio was calculated. The patients were stratified into solitary or recurrent stone formers and compared to a control group of normal children.

73 solitary and 92 recurrent stone formers were identified. Mean age was 13 years for both groups. Gender was well matched. 29 normal children served as a control group. The mean calcium-to-citrate ratio in solitary stone formers was 0.41 and in recurrent stone formers was 0.64 (p = 0.02). The mean value in normal children (0.33) was significantly lower than in recurrent stone formers (p=0.002) and trended lower compared to solitary stone forming children (p=0.15). 70% of recurrent stone formers had an abnormally high value compared to 47% of solitary stone forming patients (p=0.003).

There are significant differences in the urine calcium to citrate levels between solitary and recurrent calcium stone-forming children. Solitary stone formers trended higher compared to controls. This may allow more precise risk stratification and treatment to prevent recurrent stone episodes.

The Journal of urology. 2017 Mar 29 [Epub ahead of print]

William DeFoor, Elizabeth Jackson, Marion Schulte, Zaheer Alam, John Asplin

Children's Hospital Medical Center, Cincinnati, Ohio. Electronic address: ., Children's Hospital Medical Center, Cincinnati, Ohio., Laboratory Corporation of America® Holdings, Chicago, IL.