Urinary calcium excretion in healthy children and adolescents

Urinary calcium (Ca) excretion was determined in 1,578 24-h urine samples from 507 healthy children and adolescents (252 boys, 255 girls; 2.8–18.4 years) participating in the DONALD Study and is presented for 32 different age and sex groups. Calciuria values related to body weight (mg/kg per day) were relatively constant except for a transient decrease during puberty in all centiles, with a later onset in boys than girls. Distribution of calciuria (mg/kg per day) was best normalized by log transformation, with an almost constant standard deviation of the log-transformed values. Ca excretion was ≥4 mg/kg per day in 8.6% and ≥6 mg/kg per day in 1.5% of the urine samples. Based on Ca excretion rates of 1,080 pairs of 24-h urine samples from 364 children and adolescents, sensitivity, specificity, and the predictive value for hypercalciuria (≥4 mg/kg per day) in the next urine sample were calculated at three test levels classifying calciuria of the initial urine sample. In summary, this study presents normal values of urinary Ca excretion related to age and sex in a population of healthy German children and adolescents consuming a typical western-style diet. A high level of calciuria in a random urine sample is important in the diagnosis of hypercalciuria.