Calcium-to-Citrate Ratio Distinguishes Solitary and Recurrent Urinary Stone Forming Children

Abstract

The prevalence of urinary stone disease is increasing in children. We previously reported a high rate of urinary metabolic abnormalities, including hypercalciuria and hypocitraturia, in stone forming children. In this study we determined whether calcium-to-citrate ratio could help predict those at risk for recurrent stone formation. We conducted a retrospective cohort study to assess calcium-to-citrate ratios in children with urolithiasis. Two 24-hour urine collections were performed. Urinary excretions of calcium and citrate were analyzed, and calcium-to-citrate ratio was calculated. Patients were stratified into solitary and recurrent stone formers and compared to a control group of normal children. We identified 73 solitary and 92 recurrent stone formers. Mean patient age was 13 years for both groups. Gender was well matched. A total of 29 normal children served as controls. Mean calcium-to-citrate ratio was 0.41 in solitary stone formers and 0.64 in recurrent stone formers (p = 0.02). Mean value in normal children (0.33) was significantly less compared to recurrent stone formers (p = 0.002) and trended lower compared to solitary stone formers (p = 0.15). The ratio was abnormally high in recurrent stone formers (70%) compared to solitary stone formers (47%, p = 0.003). There are significant differences in urine calcium-to-citrate ratios between solitary and recurrent calcium stone forming children. Solitary stone formers trended higher compared to controls. These findings may allow more precise risk stratification and treatment to prevent recurrent stone episodes.