Hyponatremia in cancer patients

Hyponatremia is the most frequent electrolyte disorder in hospitalized patients but also a well known poor prognostic factor in cancer patients. Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is often misdiagnosed by oncologist because of difficulties in the interpretation of laboratory tests. Etiology is heterogeneous but the predominant cause is represented by the unbalance between excessive presence of water and serum sodium deficiency. Ectopic production of arginine vasopressin (AVP) develops more frequently in small cell lung cancer but it is not so rare in other malignancies. Neurological impairment may range from subclinical to life-threating symptoms depending by the rate of serum sodium deficiency. Appropriate diagnosis is essential to set a proper therapy. When hyponatremia is caused by SIADH, hypertonic saline infusion is indicated for acute presentation whereas fluid restriction is preferred in case of chronic asymptomatic evolution. Other options include vaptans, vasopressin receptor antagonists, targeted specifically for the correction of euvolemic hyponatremia. The aim of this brief report is to provide concise and specific informations for the management of SIADH in oncology clinical practice.