SIADH Syndrome of inappropriate antidiuretic hormone secretion

• Facts:
  Euvolemic hyponatremia (from stimulated ADH release)
• Diagnosis:
  Failure to correct with nl saline infusion
  
  URINE
  Urine osmolality > 100-150 mOsm/kg
  Increased urine sodium concentration
  
  SERUM
  Serum hyposmolality ( < 280 mOsM/Kg )
  Hyponatremia
  
• Treatment:
  Fluid restriction
  Demeclocycline / lithium (chronic treatment)
  Hypertonic saline (sodium < 110 mEq/L or symptomatic)
• Associated With:
  1) CNS dx (head injury)
  2) Subarachnoid hemorrhage (c erebral salt-wasting syndrome )
  3) Pulmonary disease ( sarcoidosis , pneumonia )
  4) Paraneoplastic syndrome ( small cell lung carcinoma )
  5) Drugs (anthipsychotics, antidepressants)
  6) Surgery
• Differential Diagnosis:
  Primary polydipsia