- We describe three cases of severe obstructive uropathy in children under 2 years of age, due to radio-lucent renal stones. Metabolic work-up revealed only normouricemic hyperuricosuria (HU) as the single identifiable risk factor for urolithiasis (UL) in these infants. We reviewed records of 66 cases of pediatric UL seen in our service over an 8-year period. UL prevalence was greater for Bedouin than for Jewish children (1.02 vs. 0.13 cases/1,000 inhabitants at risk respectively, P<0.01). HU (>0.6 mg uric acid/dl GFR) was the only biochemical risk factor that differed between Bedouin and Jewish children (mean uric acid excretion index 0.8±0.39 vs. 0.55±0.26 mg/dl GFRrespectively, P<0.05). Bedouin children comprised 85% of patients in the HU group versus 59% in the non-hyperuricosuric group (P<0.05). The mean age of onset of UL was 38±44 months and 93±52 months in the HU and the non-HU group, respectively (P<0.05). The UA excretion index in the HU group was inversely correlated with age (r=0.41, P<0.01) and its slope and constant were different from an age-matched non-UL control population. In conclusion, pediatric UL in southern Israel is predominant in Bedouin toddlers. HU was the only identifiable biochemical risk factor that could explain this difference.