Studies on the urinary calcium excretion in children with hematuria of postglomerular origin: effects of the variation of dietary calcium and sodium intake.

ABSTRACT

The effect of different dietary regimens and of an oral calcium (Ca) load was studied in 30 children with postglomerular hematuria, 8 of whom were renal stone formers. In addition we investigated the urinary inorganic phosphate complex composition in 12 of them, based on the principles of complex equilibria. Twenty-one of the 30 hematuric children with a urinary Ca/creatinine (Ca/cr) ratio of greater than or equal to 0.6 (mmol/mmol) were regarded as hypercalciuric. Low calcium intake normalised the ratio in 11 patients, fulfilling the definition of absorptive hypercalciuria, but not in the other 10 patients with renal hypercalciuria. Sodium restriction combined with low calcium diet induced a further significant decrease of the urinary Ca/cr ratio to a normal range in both forms of hypercalciuria (mean +/- SD 0.325 +/- 0.112 in absorptive hypercalciuria; 0.533 +/- 235 in renal hypercalciuria). There was a significant difference in the composition of phosphate complexes between the 6 normocalciuric patients and the 6 children with renal hypercalciuria investigated. Lithogenic urinary phosphate complexes (CaHPO4, MgHPO4) were excreted by the latter group in a significantly higher amount under basal conditions. On the basis of these data sodium restriction added to low calcium diet could represent a dietary approach in preventing excessive calcium excretion in idiopathic hypercalciuria, and therefore renal stone formation.