A 67-year-old man with small cell lung cancer has confusion. Sodium is 121 mEq/L, serum osmolality is low, urine osmolality is high, and urine sodium

Question

A 67-year-old man with small cell lung cancer has confusion. Sodium is 121 mEq/L, serum osmolality is low, urine osmolality is high, and urine sodium is 58 mEq/L. He appears euvolemic. Which of the following is the most likely explanation for this patient's findings?

Accepted Answer

Syndrome of inappropriate antidiuretic hormone secretion

Answer

Hypovolemic hyponatremia from diarrhea

Answer

Adrenal crisis with hyperkalemia as the dominant finding

Answer

Primary polydipsia

Answer

Central diabetes insipidus

SIADH — USMLE Step 3 MCQ

A 67-year-old man with small cell lung cancer has confusion. Sodium is 121 mEq/L, serum osmolality is low, urine osmolality is high, and urine sodium is 58 mEq/L. He appears euvolemic. Which of the following is the most likely explanation for this patient's findings?