Hyponatremia: The Daily PANCE Blueprint
A 55-year-old man with a recent history of head trauma is found to have a serum sodium level of 128 mEq/L. He is asymptomatic. His urine osmolality is high, and urine sodium excretion is increased. What is the most appropriate next step in the evaluation of his hyponatremia?
A. Serum osmolality measurement
B. Water deprivation test
C. CT scan of the head
D. Measurement of thyroid-stimulating hormone (TSH) and cortisol levels
E. Administration of a loop diuretic
Answer and topic summary
The answer is A. Serum osmolality measurement
In the evaluation of hyponatremia, measuring serum osmolality is crucial to determine whether the hyponatremia is hypoosmolar, isoosmolar, or hyperosmolar. This distinction is important for guiding further diagnostic and therapeutic steps. The history of head trauma and findings of high urine osmolality and increased urine sodium excretion suggest the possibility of SIADH, which is often associated with hypoosmolar hyponatremia.
Explanation for Incorrect Answers:
B. Water deprivation test: Used in the diagnosis of diabetes insipidus, not typically in the initial evaluation of hyponatremia.
C. CT scan of the head: Important in the context of head trauma but does not directly address the cause of hyponatremia.
D. Measurement of TSH and cortisol levels: Important in evaluating potential endocrine causes but after determining the osmolality.
E. Administration of a loop diuretic: Not indicated without understanding the underlying cause of hyponatremia.
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Smarty PANCE Content Blueprint Review:
Covered under ⇒ PANCE Blueprint Renal System ⇒ ⇒
Also covered as part of the Internal Medicine EOR topic list
