A nurse is comparing laboratory findings for two clients on a neuro unit. Client A has serum sodium 128 mEq/L, urine specific gravity 1.030, and urine osmolality 650 mOsm/kg. Client B has serum sodium 155 mEq/L, urine specific gravity 1.001, and urine output of 400 mL/hr. Which disorder does each client most likely have?
- A.Client A: diabetes insipidus; Client B: SIADH
- B.Client A: SIADH; Client B: diabetes insipidus
- C.Both clients have diabetes insipidus
- D.Both clients have SIADH
Show answer & rationale
Correct answer
B. Client A: SIADH; Client B: diabetes insipidus
Rationale
B is correct: SIADH (syndrome of inappropriate antidiuretic hormone) causes water retention, resulting in dilutional hyponatremia (low serum Na+) and highly concentrated urine (high specific gravity and osmolality). Client A's values, low serum sodium with concentrated urine, match SIADH. Diabetes insipidus (DI) causes failure to concentrate urine, producing high serum sodium (hypernatremia) from free-water loss, with a huge volume of very dilute urine (low specific gravity, low osmolality). Client B's values, hypernatremia, very dilute urine, and high urine output, match DI. A is incorrect: This reverses the diagnoses. C and D are incorrect: The two clients have opposite patterns and cannot both have the same condition.
Key concepts