endocrine and metabolic disorders
Syndrome of Inappropriate ADH Secretion (SIADH)
Diagnosis of SIADH
Serum and urine osmolality and electrolyte measurements showing inappropriately high urine osmolality compared to serum osmolality in a euvolemic patient Normal adrenal,thyroid,renal, cardiac and hepatic function SIADH is suspected in patients who have hyponatremia and are euvolemic (ie, neither hyper- nor hypovolemic on physical examination). 1.003). Serum sodium concentration and serum osmolality that are low and urine osmolality that is inappropriately high (120 to 150 mmol/L [120 to 150 mOsm/kg])) with respect to the low serum osmolality suggest volume overload, volume contraction, or SIADH. Volume Overload and 1% (for calculation, see Other urine tests ). Diagnosis of etiology should be pursued based on symptoms and signs. Because potentially causative medications are relatively commonly used, other etiologies must also be considered even when patients are taking such a medication. In general, a chest x-ray should be done. Central nervous system imaging can be reserved for patients in whom a brain disorder is clinically suspected or no other cause for SIADH can be found. 