Postoperative hypophysectomy: thirst and polyuria; which parameter should be checked next to assess for the expected complication?

Postoperative hypophysectomy: thirst and polyuria; which parameter should be checked next to assess for the expected complication?

• A. Serum glucose
• B. Blood pressure
• C. Respiratory rate
• D. Urine specific gravity

Answer: (D)

After a hypophysectomy, the most feared complication is diabetes insipidus caused by loss of antidiuretic hormone. When DI occurs, the kidneys cannot concentrate urine, so patients produce large volumes of dilute urine despite thirst. The quickest way to detect this is to assess urine concentration, which is what urine specific gravity measures. A low urine specific gravity indicates dilute urine consistent with DI, signaling that the patient is not conserving water and may be developing this complication. Serum glucose, blood pressure, and respiratory rate aren’t as directly informative about DI. Serum glucose would test for hyperglycemia (diabetes mellitus) but doesn’t reflect ADH-dependent water handling. Blood pressure and respiratory rate can change with dehydration but don’t specifically confirm the inability to concentrate urine. So measuring urine specific gravity provides the most direct and immediate insight into the expected postoperative complication.

After a hypophysectomy, the most feared complication is diabetes insipidus caused by loss of antidiuretic hormone. When DI occurs, the kidneys cannot concentrate urine, so patients produce large volumes of dilute urine despite thirst. The quickest way to detect this is to assess urine concentration, which is what urine specific gravity measures. A low urine specific gravity indicates dilute urine consistent with DI, signaling that the patient is not conserving water and may be developing this complication.

Serum glucose, blood pressure, and respiratory rate aren’t as directly informative about DI. Serum glucose would test for hyperglycemia (diabetes mellitus) but doesn’t reflect ADH-dependent water handling. Blood pressure and respiratory rate can change with dehydration but don’t specifically confirm the inability to concentrate urine. So measuring urine specific gravity provides the most direct and immediate insight into the expected postoperative complication.