Case Presentation: 71-year-old male with extensive smoking history was referred to the hospital by his PCP for new-onset severe hyponatremia of 117mMol/L. He denied any active complaints and initial physical examination showed an euvolemic male. Low serum osmolality of 245mOsm/kg but high urine osmolality of 309mOsm/kg and high urine sodium of 68mEq/L were suggestive of [...]