[Normal values of calcium and oxalate excretion in children].

Aim of the study was to establish normal values for calcium/creatinine (Ca/cr) and oxalate/creatinine (Ox/cr) ratio in infants and children. Urine probes of 416 healthy children (25 infants aged 1-7 days and 391 children aged 1 month-14.5 years) were analysed. Oxalate was measured by ion-chromatography. Urinary Ca2+/cr was normally distributed, Ox/cr had log-normal distribution. Ca/cr was the lowest in the first days of life, the highest between 7 month-1.5 years (mean +/- SD = 0.39 +/- 0.28 mmol/mmol), a slight decrease could be observed until 14 years (0.34 +/- 0.18). The highest Ox/cr values were measured during the first month of life (geometric mean/range/ = 133 /61-280 mmol/mmol/), followed by gradual decrease until 14 years (25/6-73/). The measurement of Ca2+/cr and Ox/cr in first morning urine samples is suitable for screening of hypercalciuria and hyperoxaluria. The interpretation of the values requires age specific reference values. Both calcium and oxalate determinations should be the part of the evaluation of patients with hematuria, hypercalciuria or nephrolithiasis.