RESULTS OF A PROSPECTIVE TRIAL TO COMPARE NORMAL URINE SUPERSATURATION IN CHILDREN AND ADULTS

Abstract

Urinary stone disease is relatively rare in children but is often due to metabolic abnormalities. Urinary supersaturation (SS) indices have been suggested as more precise predictors of stone recurrence. We previously reported urinary metabolic evaluations in stone-forming children using adult references. We now assess normal SS values in children. A prospective trial was performed to assess urinary metabolic profiles in children with no personal or family history of urinary calculi. The 24-hour urine collections were performed and evaluated at an outside central laboratory. Urine chemistries were adjusted for urine creatinine. Urine pH and SS for calcium oxalate, calcium phosphate and uric acid were also assessed. The data were compared to a cohort of normal adults. A total of 168 samples from 168 adults (58% males) and 51 samples from 30 children (59% males) were evaluated. The mean age of the children was 8.8 years (range 5 to 18). Calcium oxalate SS was similar between children and adults, and urine pH was the major cause of differences seen in the calcium phosphate and uric acid SS indices. Children had a much higher excretion of calcium, oxalate and citrate when adjusted for creatinine. There are significant differences in the normal ranges of urine chemistries in children and adults. An understanding of normal supersaturation values may allow metabolic abnormalities in stone-forming children to be more precisely diagnosed and treated.