Differing urinary urea excretion among children with idiopathic hypercalciuria and/or hyperuricosuria.

ABSTRACT

OBJECTIVE: To estimate dietary protein intake in children with idiopathic hypercalciuria (HC) and/or hyperuricosuria (HU). PATIENTS AND METHODS: We compared the 24-h urinary excretion of urea, as a reflection of protein intake, in four age- and sex-matched groups, each comprising 56 consecutive children (1) HC, (2) HU, (3) HC+HU and (4) control. RESULTS: Urinary urea excretion was significantly higher in HC, HU and HC+HU than in controls. HC and HU children had similar urea excretion. HC+HU children had urinary urea significantly higher than HC and HU, but urinary calcium similar to HC and urinary uric acid excretion similar to HU subjects. Urinary calcium was significantly (R(2)=0.21) correlated with urea excretion in HC children only, whereas urinary uric acid was significantly (R(2)=0.21) correlated with urinary urea in HU children only. No significant correlation between urinary urea and calcium or uric acid excretion was found in HC+HU patients although they had the highest urinary urea. A significant (p=0.004) interaction between urinary urea and sodium in increasing urinary calcium excretion resulted only in the HC group. CONCLUSION: The association of dietary protein excess with HC and/or HU is conditioned by an individual (genetic?) predisposition and may be produced by different mechanisms.