K. Kamoi et al., Asymptomatic hyponatremia due to inappropriate secretion of antidiuretic hormone as the first sign of a small cell lung cancer in an elderly man, INTERN MED, 37(11), 1998, pp. 950-954
A 72-year-old man was hospitalized with asymptomatic hyponatremia, Despite
hyponatremia, urinary sodium excretion with urine osmolality exceeding plas
ma osmolality persisted. Plasma vasopressin levels were high and independen
t of plasma osmolality during hypertonic saline infusion. Computed tomograp
hy of the chest showed enlarged mediastinal and right hilar lymph nodes. Mi
croscopically, a specimen of lymph nodes obtained by biopsy represented vas
opressin-producing small cell lung carcinoma. Chemotherapy plus irradiation
improved the hyponatremia, Thus, careful evaluation is necessary to determ
ine the cause of hyponatremia disorders in elderly patients.