In SIADH, what is typically observed in urine?

• A. Decreased urine osmolality
• B. Decreased urine sodium
• C. Increased urine osmolality and sodium
• D. No change in urine osmolality

Answer: (C)

In SIADH, excess ADH causes the kidneys to reabsorb water, leading to a concentrated urine even though serum osmolality is low. Because the patient is euvolemic, the kidneys continue to excrete sodium, resulting in a high urine sodium concentration. Therefore, the typical urine pattern is increased osmolality and increased sodium. If the urine were dilute (low osmolality), that would indicate appropriate ADH suppression, which isn’t the case in SIADH; similarly, a low urine sodium would suggest a different volume status or condition, not SIADH.