Hematuria of unknown origin occurs in 30% of patients with diabetic nephropathy. In nondiabetic persons, hematuria may be caused by hypercalciuria with or without nephrolithiasis. Eight children with type I diabetes mellitus, hematuria, and hypercalciuria were observed in our clinic during a 1-year period. Two of these also had evidence of renal papillary necrosis. To assess the importance of hypercalciuria in the pathogenesis of hematuria in children with diabetes mellitus, we measured urinary calcium excretion in a large population of such patients. The calcium to creatinine ratio in the urine of diabetic children (0.21 ± 0.01) was greater than that of nondiabetic children (0.12 ± 0.01). A calcium to creatinine ratio of 0.28 was established as the upper limit of normal in our nondiabetic population, and 27% of the diabetic children were hypercalciuric on this basis. The diabetic children with hypercalciuria also had hyperphosphaturia and a urinary CaHPO4.2H2O molar ion product three times that found in the nondiabetic control population. These data suggest that many children with diabetes are at risk for renal damage due to hypercalciuria. Because hypercalciuria is more common in diabetic than nondiabetic children, it may play a previously unrecognized role in the renal disease associated with diabetes mellitus.

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