Urinary calcium excretion in Swedish children

Urinary calcium excretion was measured in an unselected population of 153 healthy Swedish children aged 2-18 years. Urine was collected after an ordinary meal. Urinary calcium excretion was measured as the calcium/creatinine concentration ratio (UCa/Cr) and expressed in mmol/l per mmol/l. UCa/Cr was 0.44 +/- 0.379 (mean +/- SD). As the UCa/Cr in this childhood population was not distributed in a normal manner, the results are more correctly presented as the 50th (0.33) and 97th (1.5) centiles. There was a weak but significant correlation between UCa/Cr and age, with higher values in the lower age groups. There was no correlation between UCa/Cr and the anamnestic intake of cow's milk. Repeated samples from some children showed a coefficient of variation between days of 30-40%. The upper limits of normal UCa/Cr (97th centile = 1.5; +2 SD = 1.2) in this investigation were higher than what is considered normal by others. In spite of this, none of the children had a history of renal stone disease or any other symptoms of hypercalciuria. Renal stone disease is thought to be rare in Swedish children although the real incidence is not known. The diagnosis of hypercalciuria should be based on repeated samples from an individual with symptoms and related to age-related reference values from the same population group.