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Difficulty: HardDiagnostic Workup and Test Sequencing

A 3434-year-old woman presents to the clinic with new-onset headaches, palpitations, and severe muscle cramps. Her blood pressure is 172/106172/106 mmHg. A basic metabolic panel reveals a serum sodium of 144144 mEq/L and a serum potassium of 2.82.8 mEq/L. She is not taking any medications and has no family history of early-onset hypertension. The physician suspects an endocrine etiology for her secondary hypertension. Assuming each investigative step confirms the indication for the next and the patient is a candidate for surgical management, arrange the following diagnostic steps in the correct, guideline-directed chronological sequence from initial workup to preoperative planning.

  1. 1Measurement of the plasma aldosterone concentration to plasma renin activity (PAC/PRA) ratio
  2. 2Intravenous saline infusion test
  3. 3High-resolution computed tomography (CT) of the adrenal glands
  4. 4Adrenal vein sampling (AVS)

Answer

The correct diagnostic sequence is: 1) Measurement of the plasma aldosterone concentration to plasma renin activity (PAC/PRA) ratio, 2) Intravenous saline infusion test, 3) High-resolution computed tomography (CT) of the adrenal glands, and 4) Adrenal vein sampling (AVS).
The diagnostic workup for primary hyperaldosteronism requires a strict, tiered approach. It begins with initial screening using the plasma aldosterone concentration to plasma renin activity (PAC/PRA) ratio. If elevated, the diagnosis must be confirmed by demonstrating autonomous aldosterone production that fails to suppress during an intravenous saline infusion test (or an oral sodium loading test). Once the condition is biochemically confirmed, anatomical imaging with high-resolution adrenal CT is performed to rule out large carcinomas and delineate the regional anatomy. Finally, because CT cannot differentiate a highly prevalent non-functioning adrenal incidentaloma from a functioning adenoma, adrenal vein sampling (AVS) is required to functionally lateralize the source of excess aldosterone before a surgeon can safely proceed with an adrenalectomy.

Step-by-Step Solution

1
Screen for hyperaldosteronism
Measurement of the PAC/PRA ratio
This is the most sensitive initial screening modality for primary hyperaldosteronism in high-risk patients (e.g., severe hypertension with unprovoked hypokalemia).
2
Confirm autonomous aldosterone secretion
Intravenous saline infusion test
To rule out false-positive screening results, a confirmatory test must demonstrate that the elevated aldosterone level fails to suppress despite physiologic sodium and volume loading.
3
Localize the source anatomically
High-resolution CT of the adrenal glands
After biochemical confirmation, imaging identifies macroscopic abnormalities, rules out malignant adrenocortical carcinoma, and provides crucial venous mapping for subsequent interventions.
4
Lateralize the functional source of hormone excess
Adrenal vein sampling
Because non-functioning adrenal incidentalomas are common, structural imaging alone can be misleading. AVS functionally confirms whether the excess aldosterone is originating unilaterally (curable by surgery) or bilaterally (managed medically).

Key Concept

The diagnostic algorithm for primary hyperaldosteronism must strictly follow four escalating tiers to avoid misdiagnosis and inappropriate surgery: screening (PAC/PRA ratio), biochemical confirmation (saline suppression test), anatomical localization (adrenal CT), and functional lateralization (adrenal vein sampling).
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Diagnostic Workup and Test Sequencing

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