Role of vagal neuropathy in the hyponatraemia of alcoholic cirrhosis.

The hyponatraemia common in decompensated cirrhosis arises in part from secretion of antidiuretic hormone attributed to a decrease in effective blood volume. Baroreceptors send inhibitory impulses to the midbrain and hypothalamus through the vagus and glossopharyngeal nerves. Since vagal neuropathy often occurs in chronic alcoholism, this might theoretically contribute to the inappropriate secretion of antidiuretic hormone, which might in turn induce hyponatraemia. In a prospective study including 34 patients with cirrhosis a high incidence of vagal neuropathy was found in the alcoholics (64%) and a clear cut increase in the incidence of hyponatraemia in patients with evidence of vagal damage and ascites (seven of eight patients (88%); p = 0.02). Results of a retrospective study of 64 patients with cirrhosis and ascitic decompensation showed hyponatraemia in 17 (50%) of 34 alcoholics but in only four (13%) of 30 patients with non-alcoholic disease (p = 0.006). Vagal neuropathy in alcoholic cirrhosis may contribute to the low serum sodium concentrations commonly found in these patients.