Urinary oxalate excretion in urolithiasis and nephrocalcinosis

Aims-To investigate urinary oxalate excretion in children with urolithiasis and/or nephrocalcinosis and to classify hyperoxaluria (HyOx). Methods-A total of 106 patients were screened. In those in whom the oxalate : creatinine ratio was increased, 24 hour urinary oxalate excretion was mea sured. Liver biopsy and/or genomic analysis was performed if primary hypero xaluria (PW) was suspected. Stool specimens were examined for Oxalobacter f ormigenes in HyOx not related to PH type 1 or 2 (PH1, PH2) and in controls. Results-A total of 21 patients screened had HyOx (>0.5 mmol/24 h per 1.73 m (2)); they were classified into five groups. Eleven had PH (PH1 in nine and neither PH1 nor PH2 in two). Six had secondary HyOx: two enteric and four dietary. Four could not be classified. Seven patients had concomitant hyper calciuria. Only one of 12 patients was colonised with O formigenes compared to six of 13 controls. Conclusions-HyOx is an important risk factor for urolithiasis and nephrocal cinosis in children, and can coexist with hypercalciuria. A novel type of P H is proposed. Absence of O formigenes may contribute to HyOx not related t o PH1.