Hyponatraemia in patients with cirrhosis. Hyponatraemia occurs in nearly half of patients in hospital with cirrhosis and ascites, and is due to the excessive retention of free water which results from the kidney's inability to excrete it normally. The morbidity and mortality associated with hyponatraemia is largely attributable to central nervous system disturbances. The degree to which brain water content increases depends on the duration of hyponatraemia and on compensatory mechanisms. Altered steroid and peptide hormones in cirrhotic patients may contribute to the development of hyponatraemic encephalopathy, symptoms of which overlap with hepatic encephalopathy and uraemia. The occurrence of central pontine myelinolysis is unrelated to the rate of correction of hyponatraemia. The appearance of hyponatraemia in cirrhotic patients, long regarded as a poor prognostic sign, may be a function of unrecognized underlying impaired renal function. Therapy for hyponatraemia remains suboptimal. 