Sodium losing renal disease: Two cases and a review of the literature.

Two patients with sodium-losing renal disease were studied in detail. Both presented with shock and hypotension which was attributed at first to other causes, as was the recurrent hyponatraemia in one of them. In both patients the cause of the sodium loss was probably unrelieved urinary obstruction which has been reported previously to cause water loss but not sodium loss. Both patients had severe hyponatraemia when they were sodium depleted, which has previously been attributed to water retention from excessive secretion of antidiuretic hormone. Plasma arginine vasopressin concentrations were raised in one patient but not in the other. The cause of the water retention in the other patient is not known. One of the patients, like others described in the literature, was only able to vary his sodium excretion within narrow limits. He became sodium depleted on a normal intake and oedematous when he was given saline intravenously. We suggest that the term sodium-losing renal disease should be replaced by the term 'fixed sodium' excretion renal disease.