The Syndrome of Inappropriate Antidiuretic Hormone Secretion in the Elderly

OBJECTIVE: To determine clinical characteristics of elderly patients presenting with the syndrome of inappropriate antidiuretic hormone secretion (SIADH), their outcome, and the extent of evaluation that is warranted. DESIGN: A retrospective study. SETTING: An 800-bed primary and tertiary care center in Jerusalem, Israel. PATIENTS: Fifty elderly patients, hospitalized with serum sodium levels below 130 mmol/L consistent with a diagnosis of SIADH. MEASUREMENTS: Data collection of the medical history, functional status, physical examination, laboratory evaluation, length of hospital stay, treatment, and outcome. RESULTS: The neurological clinical presentation on admission ranged widely: 48% were fully alert, 42% were stuporotic, and 10% had seizures. Sensorial impairment was significantly associated only with sodium values of less than 110 mmol/L. The majority of patients underwent a comprehensive work-up including chest x-ray, computerized tomography (CT) scans, and thyroid and adrenal function tests. The cause of SIADH in most of the patients remained obscure (60% of cases were idiopathic). The 2 main causes identified were pneumonia in 9 cases (18%) and medication in 6 cases (12%). Most of the patients survived the event; only two patients died, both because of sepsis and not due to hyponatremia. The average hospital stay was 12.8 ± 9 days. CONCLUSIONS: Elderly patients with SIADH usually have an idiopathic form of this condition and a benign course. Extensive routine diagnostic procedures are not warranted. Simple measures like medical history taking with special emphasis on medications, physical examination, and chest x-rays can lead to a treatable diagnosis in most patients who do not have the idiopathic form of SIADH.