[Hypouricaemia in the syndrome of inappropriate ADH secretion (SIADH) (author's transl)].

A retrospective study of 22 patients with hyponatraemia (less than 130 mEq/l) was conducted to find out whether hypouricaemia was useful in the diagnosis of SIADH. Serum levels of uric acid were inferior to 38 mg/l in 9 out of 12 patients with SIADH but not in the remaining 10 patients without SIADH. The mechanism of hypouricaemia in the syndrome seems to be an increase in uric acid excretion, since water restriction reduces the fractional clearance of urates. The authors conclude that hypouricaemia appears to constitute a reliable means of detecting SIADH in patients with hyponatraemia.