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Difficulty: EasyEndocrinology and Metabolism

A 49-year-old man is evaluated in the clinic for persistently elevated blood pressure despite adherence to a three-drug antihypertensive regimen, including a thiazide diuretic. Recent laboratory results reveal a serum potassium level of 2.9 mEq/L (spontaneous hypokalemia). The physician strongly suspects primary hyperaldosteronism. Arrange the steps of the diagnostic workup and management for this condition in the correct sequential order from initial screening to final pre-surgical evaluation.

  1. 1Measurement of early morning plasma aldosterone concentration and plasma renin activity
  2. 2Intravenous saline infusion or oral sodium loading test
  3. 3Cross-sectional imaging of the adrenal glands with computed tomography
  4. 4Bilateral adrenal venous sampling

Answer

The correct sequence is: Measurement of plasma aldosterone concentration and renin activity -> Intravenous saline infusion test -> Adrenal computed tomography -> Bilateral adrenal venous sampling.
The evaluation of primary hyperaldosteronism follows a strict, step-wise algorithm: Screen -> Confirm -> Localize -> Differentiate. First, screen with the aldosterone-to-renin ratio. Second, confirm autonomous secretion with a salt loading test. Third, obtain an adrenal CT for anatomical localization. Finally, perform adrenal venous sampling to prove functional lateralization before offering unilateral adrenalectomy.

Step-by-Step Solution

1
Identify the need for screening.
The patient has resistant hypertension and spontaneous hypokalemia, making primary hyperaldosteronism highly likely.
Clinical presentation warrants screening using the plasma aldosterone concentration to plasma renin activity (PAC/PRA) ratio.
2
Confirm the diagnosis biochemically.
Perform a sodium loading test (intravenous saline infusion).
A positive screening test must be confirmed by demonstrating that aldosterone remains inappropriately elevated despite volume expansion and salt loading.
3
Localize the source of excess aldosterone.
Obtain an adrenal computed tomography (CT) scan.
Imaging is required to assess adrenal anatomy, detect distinct adenomas, and rule out large masses suspicious for adrenocortical carcinoma.
4
Differentiate between unilateral and bilateral disease.
Perform bilateral adrenal venous sampling (AVS).
Because non-functioning adrenal incidentalomas are common, AVS is necessary in surgical candidates to prove that the biochemically active source of aldosterone lateralizes to one specific gland.

Key Concept

Diagnostic algorithm for primary hyperaldosteronism
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Topics

Endocrinology and Metabolism

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