During a routine primary care visit, a 42-year-old man is evaluated for persistently eleva… — USMLE Step 3

During a routine primary care visit, a 42-year-old man is evaluated for persistently elevated blood pressure. He was diagnosed with hypertension four years ago. Despite documented adherence to a daily regimen containing maximal doses of amlodipine, olmesartan, and chlorthalidone, his home blood pressure readings consistently remain above $150/90 \text{ mm Hg}$ . He reports no headaches, palpitations, or episodic sweating. Today, his blood pressure is $162/98 \text{ mm Hg}$ , and his pulse is $76/\text{min}$ . His body mass index is $26 \text{ kg/m}^2$ . Physical examination is unremarkable. Laboratory studies from last week demonstrate a serum potassium level of $2.9 \text{ mEq/L}$ and a sodium level of $144 \text{ mEq/L}$ . A plasma aldosterone-to-renin ratio is significantly elevated, and primary aldosteronism is subsequently confirmed via a lack of aldosterone suppression following an intravenous saline infusion test. An unenhanced computed tomography (CT) scan of the abdomen reveals a $1.4\text{-cm}$ , lipid-rich, low-density nodule in the right adrenal gland. The left adrenal gland appears morphologically normal. The patient is otherwise healthy, has a good baseline functional status, and expresses a strong preference for definitive surgical management over lifelong medical therapy. Which of the following is the most appropriate next step in management?

Adrenal vein samplingAnswer
B
Right-sided laparoscopic adrenalectomy
C
Initiation of spironolactone therapy
D
Dexamethasone suppression test
E
Metaiodobenzylguanidine (MIBG) scintigraphy

Answer

The most appropriate next step is adrenal vein sampling.

The correct sequence for the diagnostic workup of primary aldosteronism in a surgical candidate is: 1) biochemical screening (aldosterone-to-renin ratio), 2) biochemical confirmation (e.g., oral sodium loading or saline infusion test), 3) adrenal imaging (CT scan), and 4) functional lateralization via adrenal vein sampling (AVS). AVS is standard of care for patients older than 35 because the incidence of non-functioning adrenal incidentalomas rises significantly with age. If surgery is performed based on CT findings alone, a non-functioning incidentaloma might be removed while the true source of aldosterone (such as bilateral adrenal hyperplasia) is left behind. Only patients under age 35 with marked primary aldosteronism and a clear unilateral adenoma on CT can safely bypass AVS.

Step-by-Step Solution

Identify the confirmed diagnosis.

The patient has biochemically confirmed primary aldosteronism, evidenced by an elevated aldosterone-to-renin ratio and a positive saline infusion suppression test.

Establishing the biochemical diagnosis is the required first step before localizing the source of hormone excess.

Analyze the imaging results and patient demographics.

CT shows a unilateral right adrenal nodule in a 42-year-old patient who desires definitive surgical management.

Treatment pathways diverge based on whether the patient is a surgical candidate and their age, as the prevalence of non-functioning adrenal masses increases with age.

Apply diagnostic test sequencing guidelines for primary aldosteronism.

Determine that adrenal vein sampling is required to confirm lateralization of aldosterone hypersecretion.

Because non-functioning adrenal incidentalomas are common in adults over age 35, imaging alone cannot reliably confirm that the visible nodule is the active source. Adrenal vein sampling prevents inappropriate adrenalectomy in cases where the true pathology is bilateral hyperplasia.

Key Concept

In patients older than 35 with confirmed primary aldosteronism and a unilateral adrenal mass on CT who desire surgery, adrenal vein sampling is required to differentiate a unilateral aldosterone-producing adenoma from bilateral adrenal hyperplasia.

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