Kidney function during hydropenia nad water diuresis in patients with idiopathic recurring nephrolithiasis.

The kidney function of 41 patients with idiopathic recurring kidney stones was investigated by inulin- and PAH-clearances and by measuring the excretion of electrolytes during hydropenia and water diuresis. All patients had normal inulin- and PAH-clearances and normal concentrating capacity as indicated by free water reabsorption (Tc H2O). Seven patients, all of whom had previously been found to have low excretion of magnesium in urine, were unable to dilute their urine. During water diuresis these patients also had lower osmolar clearance and lower excretion of sodium than the other patients. A defective dilution capacity may be of pathogenetic significance for stone formation; the causes of the defect, however, are not clear.