Idiopathic hypercalciuria in children--how valid are the existing diagnostic criteria?

Idiopathic hypercalciuria is a common metabolic abnormality in children of all ages. There is evidence of an association of idiopathic hypercalciuria with nephrolithiasis, hematuria, and osteoporosis. However, much of this evidence is anecdotal and the precise role of hypercalciuria in the pathogenesis of these conditions is far from clear. Furthermore, the precise definition of idiopathic hypercalciuria has not yet been established. The methodologies for quantitating urinary calcium excretion have also not been standardized, adding another potential confounding factor to the accurate interpretation of urinary calcium excretion. Long-term studies on the natural history of unselected children with idiopathic hypercalciuria are needed to establish the true clinical significance of this condition. The focus of this review is to critically evaluate the methods currently being used to measure urinary calcium excretion in children and to assess the validity of existing criteria for diagnosing idiopathic hypercalciuria.