Euvolemic Hyponatremia Secondary to the Syndrome of Inappropriate Antidiuresis.

Euvolemic hyponatremia is the most common cause of hyponatremia in both hospitalized patients and outpatients. The most common etiology of euvolemic hyponatremia is the syndrome of inappropriate antidiuresis (SIAD). Diagnosis of SIAD involves evaluation of a set of long-standing clinical and laboratory criteria for this diagnosis. Many treatment options for SIAD exist, and choosing among them should be based on the chronicity of the hyponatremia and neurological symptomatology. Importantly, clinical judgment and risk/benefit analysis that is individualized for specific patients should drive therapeutic decisions, because there is no single treatment that represents the "best" therapy for all patients with SIAD.