[Analysis of the urinary risk factors of urolithiasis in healthy children].

Since incidence of idiopathic calcium oxalate urolithiasis in children was very low, a study was made to analyze the risk factors of calcium oxalate stone in male volunteers without any episode of urolithiasis. They were divided into four groups, group I: eight years old, group II: 11 years old, group III: 18 to 24 years old, group IV: 41 to 45 years old. Inhibitory activities of urine were significantly higher in groups of children than in groups of adults. However, inhibitory activities of filtered urine, extracted through filters with conserved limit of 25000 of molecular weight, were reduced significantly. Therefore, it was suggested that materials with molecular weight over 25000 participated in the inhibitory activities. Furthermore, the activities of filtered urine of group I were still higher than those of the non-filtered urine in groups of adults. Accordingly it was considered that substances less than 25000 of molecular weight also participated in the inhibitory activities in children. An analysis of uric acid, citrate, magnesium and uronic acid in urine revealed that magnesium excretion volume and magnesium concentration ratio to creatinine were higher in children than in adults. Magnesium seemed to boost the inhibitory activities in children. In the measurement of crystalloid materials, the concentration of calcium was significantly lower in children groups than in groups of adults. It seemed that calcium also takes part in reduction of incidence of urinary stone in children.