ABSTRACT
The term syndrome of inappropriate antidiuresis has recently replaced the term syndrome of inappropriate antidiuretic hormone because up to 20% of patients who fulfill the criteria for SIAD do not have detectable circulating levels of vasopressin. SIAD is a diagnosis of exclusion. Patients must meet the following criteria: clinical euvolemia, hypotonic plasma, urine less than maximally dilute (urine osmolality in SIAD is greater than serum osmolality or >100-150 mOsm/kg), urinary sodium matches intake, absence of hypoadrenalism and hypothyroidism, and improvement with water restriction. Important clinical clues are low serum levels of uric acid, creatinine, and blood urea nitrogen (BUN). Some of the causes of SIAD include small cell carcinoma of the lung, central nervous system disorders, and drugs such as haloperidol, fluoxetine, and chlorpropamide.
