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Difficulty: MediumEndocrinology and Metabolism

A 4848-year-old man presents for a follow-up visit regarding his hypertension. He is currently taking maximum tolerated doses of lisinopril, amlodipine, and hydrochlorothiazide. His blood pressure is 168/102168/102 mmHg. Laboratory studies reveal a serum sodium of 143143 mEq/L and a serum potassium of 2.82.8 mEq/L. The patient is suspected to have a secondary cause of hypertension. Arrange the following diagnostic and management steps in the most appropriate chronological sequence for the evaluation and definitive management of this patient's suspected condition.

  1. 1Measurement of plasma aldosterone concentration to plasma renin activity ratio
  2. 2Intravenous saline infusion test
  3. 3Computed tomography of the adrenal glands
  4. 4Bilateral adrenal venous sampling
  5. 5Laparoscopic unilateral adrenalectomy

Answer

The correct sequential approach is: 1) Screening with plasma aldosterone to renin ratio, 2) Confirmation with a saline infusion test, 3) Anatomical localization with adrenal CT, 4) Functional localization with adrenal venous sampling, and 5) Definitive surgical management with unilateral adrenalectomy.
The algorithm for diagnosing and treating primary aldosteronism must proceed stepwise to prevent unnecessary surgery. Screening is performed first with the PAC/PRA ratio. If elevated, the diagnosis must be confirmed by demonstrating inappropriate aldosterone secretion despite volume expansion (e.g., saline infusion test). Only after confirmation should a CT scan be obtained for anatomical localization. However, because adrenal incidentalomas are highly prevalent in patients older than 3535, a CT scan alone cannot prove a nodule is functioning. Therefore, bilateral adrenal venous sampling is essential to confirm lateralization of aldosterone excess before a patient can undergo a unilateral adrenalectomy.

Step-by-Step Solution

1
Screen for primary aldosteronism
Obtain plasma aldosterone concentration (PAC) to plasma renin activity (PRA) ratio
This is the most appropriate first-line screening test for patients presenting with the classic triad of resistant hypertension, hypokalemia, and likely secondary etiology.
2
Confirm autonomous aldosterone secretion
Perform an intravenous saline infusion test or oral salt loading
A positive screening test must be confirmed biochemically by demonstrating the failure to suppress aldosterone secretion with sodium loading.
3
Anatomically localize the suspected source
Obtain a computed tomography (CT) scan of the adrenal glands
Once confirmed biochemically, imaging identifies whether there is a distinct adenoma, bilateral nodular disease, or normal-appearing glands.
4
Functionally lateralize the hormone secretion
Perform bilateral adrenal venous sampling
Because non-functioning adrenal incidentalomas are common in patients over 3535, venous sampling is required to prove that the nodule seen on CT is actually the source of the excess aldosterone.
5
Provide definitive treatment
Perform laparoscopic unilateral adrenalectomy
Surgery is the ultimate treatment of choice for confirmed, functionally unilateral aldosterone-producing adenomas.

Key Concept

The sequential diagnostic workup of primary aldosteronism strictly follows a pathway of screening (PAC/PRA ratio), biochemical confirmation (salt loading), anatomical imaging (CT), and functional lateralization (adrenal venous sampling) prior to considering surgical intervention.
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Topics

Endocrinology and Metabolism

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