[Can water be poisonous?].

HISTORY AND ADMISSION FINDINGS: Two female patients aged over 80 years developed central nervous symptoms after drinking large amounts of water (more than 3 l per day).

INVESTIGATIONS: Both had a hypoosmolar hyponatremia that was induced by concomitant treatment with hydrochlorothiazid (HCT) in the one case and in the other case relied on a distal tubular damage due to reflux nephropathy.

DIAGNOSIS, TREATMENT AND COURSE: Hyponatremia was corrected after withdrawal of HCT and fluid restriction and central nervous symptoms disappeared rapidly.

CONCLUSIONS

Distal tubular urinary dilution can be disturbed by HCT and parenchymal renal disease and can result in symptomatic hyponatremia after drinking large amounts of water.