Cyrill with severe head trauma sustained in a car accident is admitted to the intensive care unit. Thirty-six hours later, the client’s urine output suddenly rises above 200 ml/hour, leading the nurse to suspect diabetes insipidus. Which laboratory findings support the nurse’s suspicion of diabetes insipidus?
A. Above-normal urine and serum osmolality levels.
B. Below-normal urine and serum osmolality levels.
C. Above-normal urine osmolality level, below-normal serum osmolality level.
D. Below-normal urine osmolality level, above-normal serum osmolality level.
Correct Answer: D. Below-normal urine osmolality level, above-normal serum osmolality level
In diabetes insipidus, excessive polyuria causes dilute urine, resulting in a below-normal urine osmolality level. At the same time, polyuria depletes the body of water, causing dehydration that leads to an above-normal serum osmolality level.
Option A: Urine osmolality level should be below normal because of excessive polyuria.
Option B: Serum osmolality levels should be above normal because of dehydration.
Option C: For the same reasons, diabetes insipidus doesn’t cause above-normal urine osmolality or below-normal serum osmolality levels.