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Difficulty: HardEndocrinology and Metabolism

A 4848-year-old man is evaluated for resistant hypertension. His blood pressure is 168/104 mm Hg168/104 \text{ mm Hg} despite strict adherence to maximum-dose amlodipine, lisinopril, and hydrochlorothiazide. He reports recent episodes of muscle cramping and significant fatigue. Laboratory studies reveal a serum potassium level of 2.9 mEq/L2.9 \text{ mEq/L} and a serum sodium level of 146 mEq/L146 \text{ mEq/L}. The physician suspects a specific endocrine etiology for his secondary hypertension. Arrange the following diagnostic and management steps in the most appropriate chronological sequence for this patient.

  1. 1Measurement of the early-morning plasma aldosterone concentration to plasma renin activity ratio
  2. 2Administration of an intravenous isotonic saline suppression test
  3. 3Cross-sectional computed tomography of the adrenal glands
  4. 4Bilateral adrenal venous sampling
  5. 5Unilateral laparoscopic adrenalectomy

Answer

The correct sequence is: (1) Screening with plasma aldosterone-to-renin ratio, (2) Confirmatory saline suppression test, (3) Anatomical localization with adrenal CT, (4) Functional confirmation with adrenal venous sampling, and (5) Definitive treatment with unilateral adrenalectomy.
The diagnostic workup of primary hyperaldosteronism strictly follows a protocol designed to prevent the surgical removal of nonfunctioning adrenal incidentalomas. The cascade requires biochemical screening (aldosterone-to-renin ratio) to detect potential cases. Positive screens require biochemical confirmation (saline suppression test) to prove autonomy. Once confirmed, anatomical localization (CT scan) identifies structural abnormalities. However, because incidentalomas are highly prevalent in patients older than 3535, structural abnormalities must undergo functional lateralization (adrenal venous sampling) to prove the visible nodule is actively secreting aldosterone. Only after AVS lateralizes the hypersecretion to one gland is unilateral adrenalectomy indicated. If AVS shows bilateral hypersecretion, the patient is treated medically with mineralocorticoid receptor antagonists (e.g., spironolactone).

Step-by-Step Solution

1
Perform initial biochemical screening for primary hyperaldosteronism.
Obtain an early-morning plasma aldosterone concentration (PAC) and plasma renin activity (PRA).
Patients with resistant hypertension accompanied by spontaneous or diuretic-induced hypokalemia have a high pretest probability for primary hyperaldosteronism and require a screening PAC/PRA ratio.
2
Confirm autonomous aldosterone secretion.
Perform a suppression test, such as the intravenous saline infusion test.
The PAC/PRA ratio is highly sensitive but can yield false positives. A confirmatory test demonstrating the failure of aldosterone to suppress under volume expansion proves autonomous secretion.
3
Anatomically localize the suspected lesion.
Obtain a high-resolution CT scan of the abdomen.
Imaging distinguishes between bilateral adrenal hyperplasia, a unilateral adenoma, and rarer conditions like adrenocortical carcinoma. It must follow, not precede, biochemical confirmation.
4
Confirm functional lateralization of the hormone hypersecretion.
Perform bilateral adrenal venous sampling (AVS).
Because nonfunctioning adrenal adenomas (incidentalomas) are found in up to 10%10\% of patients over age 4040, AVS is required to prove that the radiologically identified nodule is the actual source of aldosterone before removing the gland.
5
Provide definitive treatment for the identified pathology.
Proceed with unilateral laparoscopic adrenalectomy.
Surgery is the definitive cure for a biochemically active, functionally lateralized unilateral aldosterone-producing adenoma.

Key Concept

The precise, stepwise diagnostic and management algorithm for primary hyperaldosteronism.
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Topics

Endocrinology and Metabolism

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