Pediatric Nephrolithiasis- clinical manifestations and metabolic characteristics data from a dedicated clinic

Background: Pediatric nephrolithiasis (NL) prevalence has increased in the past two decades. NL recurrence is commoner in children, due to the high incidence of abnormal metabolic risk factors. Still, the detection rate of these metabolic abnormalities and the relative role of monogenic abnormalities is not well defined.

Methods: Retrospective review of 83 patients who presented to our dedicated multidisciplinary NL clinic between 02/2016-07/2018. To define or exclude a specific metabolic abnormality, at least 2 separate metabolic evaluations were done (24 hour urinary collection or spot samples for not toilet trained children).

Results: Mean age at first stone presentation was 7.7±5.7 years, 60% were boys, 14 (17%) had a family history of NL, 58 (70%) were symptomatic at presentation, 22 (26.5%) had an anatomic abnormality (mostly UPJ stenosis). Full metabolic evaluation was completed in 76/ 83 patients. At least 1 abnormal metabolic risk factor was found in 61 of them (80%) including: hypercalciuria (HCa) in 37 (49%), hypocitraturia (HCit) in 28 (37%), hyperoxaluria (HO) in 15 (22%), cystinuria in 4 (5%) and hyperuricosuria in 3 (4%). An apparent monogenic abnormality was found in 12/83 (14%) of the children including: primary hyperoxaluria (type 1 or 3) (n= 6), CYP24A1 (n=2), SLC3A (n=1), cystinuria (n=2) and distal RTA in 1. 47/61 (77%) had a therapeutic measure tailored for their metabolic abnormality.

In summary: using a thorough investigation, a modifiable risk factor for NL (most of them: apparently non monogenic) can be found in a high percentage of pediatric patients.