Hyperuricosuria in children: clinical presentation and natural history.

OBJECTIVE: Idiopathic hyperuricosuria (HU) was previously reported in only a limited number of children with hematuria. We aimed to outline the clinical presentation and natural history of HU not only in children with hematuria, but also in those with dysuria and/or recurrent abdominal/flank pain and a family history of urolithiasis.

STUDY DESIGN: Retrospective analysis of data at diagnosis from 102 consecutive children with HU and outcome analysis of 26 of them who were followed >/=1 years (mean: 3.1) with no specific therapy.

RESULTS: Sixty-one participants had HU and 41 had HU + hypercalciuria. Fifty-two patients had no hematuria among the presenting symptoms, more than one third had normal urinalysis at our first examination, one half had microcalculi (<3 mm in diameter) at renal sonography, and 12% had stones (4-18 mm). Thirty participants of the 39 with no hematuria at our first examination (77%) showed microcalculi or calculi at renal sonography. The patients with microcalculi were significantly older than were those without microcalculi. During the follow-up, 4 of 26 children never had hematuria and 8 had no hematuria during most of the follow-up period. Two patients who had a calculus at first visit and 3 who formed calculi 4 to 12 mm in diameter, after 1 to 3.5 years subsequently passed them in the urine.

CONCLUSIONS: The lack of hematuria is not predictive of absence of urolithiasis. Therefore, it may be misleading to judge on the efficacy of a given therapy only based on disappearance of hematuria. HU and hypercalciuria have to be suspected in children with dysuria and those with recurrent abdominal/flank pain and familial history of urolithiasis, although they have no hematuria.