A68-year-old man is brought to the emergency department by because of worsening confusion for the past week. His wife says that he had a nagging cough that seemed to worsen over the past several months and that he began experiencing occasional dizziness earlier this week. He has a history of an ischemic stroke 4 months ago. Current medications are aspirin. He is lethargic and disoriented. His pulse is 78/min, and blood pressure is 135/88 mm Hg. Physical examination shows moist oral mucosa, normal skin turgor, and no peripheral edema. Laboratory results are as follows: Chest x-ray reveals a mass in the right lung. Which of the following additional findings is most likely to be present in this patient?

Question

A68-year-old man is brought to the emergency department by because of worsening confusion for the past week. His wife says that he had a nagging cough that seemed to worsen over the past several months and that he began experiencing occasional dizziness earlier this week. He has a history of an ischemic stroke 4 months ago. Current medications are aspirin. He is lethargic and disoriented. His pulse is 78/min, and blood pressure is 135/88 mm Hg. Physical examination shows moist oral mucosa, normal skin turgor, and no peripheral edema. Laboratory results are as follows:  Chest x-ray reveals a mass in the right lung.  Which of the following additional findings is most likely to be present in this patient?

Quizplus · Accepted Answer

Eductional Objective: The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is characterized by low plasma sodium and osmolality, inappropriately concentrated urine, and clinically normal volume status (euvolemic hyponatremia).  An important cause of SIADH is a paraneoplastic effect secondary to small cell carcinoma of the lung.

A68-Year-Old Man Is Brought to the Emergency Department by Because