<prompt> The syndrome of inappropriate antidiuretic hormone is characterized by the following :Hyponatremia and urine sodium excretion 20 meqlHypernatremia and urine sodium excretion 20 meqlHyponatremia and hyperkalemiaHypernatremia and hypokalemia  <response>: Answer is A Hyponatremia and urine sodium excretion 20 meql : Cardinal features of SIADH include: Hyponatremia dilutional hyponatremia with Na 135 mmol1 Decreased plasma osmolality 150 m osm. Urine sodium over 20 meq1 Low Blood urea Nitrogen 10 mgL Hypouricemia Clinical Euvolemia - Absence of sign of hypervolemia edema, ascitis - Absence of signs of hypovolemia ohostatic hypotension, tachycardia, features of dehydration Absence of cardiac, liver or renal disease Normal thyroid and adrenal function A high BUN suggests a volume contracted state and excludes a diagnosis of SIADH. Q 