Primary Aldosteronism: When Adrenal Venous Sampling Is Not Needed Before Unilateral Adrenalectomy

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There is a small subset of patients (≈5%) with primary aldosteronism (PA) in whom surgical management can proceed without the need for adrenal venous sampling (AVS). This subset includes those patients with the following characteristics: young (≤35 years), marked PA as demonstrated by spontaneous hypokalemia and plasma aldosterone concentration >30 ng/dL, and unilateral macroadenoma on adrenal computed tomography (CT) scan.

Case Report

The patient was a 35-year-old man with a 4-year history of hypertension. He was treated with a three-drug program: central α ₂ -agonist (clonidine 0.2 mg daily), calcium channel blocker (amlodipine 10 mg daily), and an angiotensin receptor blocker (valsartan 80 mg daily). Blood pressure control with these three medications was good. However, spontaneous hypokalemia had become a major problem requiring hospitalization on two occasions for potassium chloride infusions. At the time of referral to Mayo Clinic he was taking 80 mEq of potassium chloride daily to maintain a normal serum potassium concentration. Beyond hypertension and hypokalemia, the patient was healthy. He had no signs or symptoms of Cushing syndrome. He had no first-degree relatives who had been diagnosed with hypertension.

INVESTIGATIONS

The baseline laboratory test results are shown in Table 7.1 . The patient had positive case detection testing for PA with a plasma aldosterone concentration (PAC) >10 ng/dL and plasma renin activity (PRA) <1.0 ng/mL per hour. In addition, PA was confirmed because when a patient has spontaneous hypokalemia and the PAC >20 ng/dL, there are no other differential diagnostic possibilities beyond PA. ^, Thus formal confirmatory testing with oral sodium loading or a saline infusion test was not needed for this patient. The serum dehydroepiandrosterone sulfate (DHEA-S) concentration was mid-normal and cortisol suppressed normally with an overnight 1-mg dexamethasone suppression test (DST) ( Table 7.1 ). Thus the adrenal adenoma was not cosecreting cortisol.

TABLE 7.1

Laboratory Tests

Biochemical Test	Result	Reference Range
Sodium, mmol/LPotassium, mmol/LCreatinine, mg/dLAldosterone, ng/dLPlasma renin activity ng/mL per hourDHEA-S, mcg/dL1-mg overnight DST	1424.11.254<0.6290<1.0	135–1453.6–5.20.8–1.3≤21 ng/dL≤0.6–357–522<1.8

DHEA-S , Dehydroepiandrosterone-sulfate; DST , dexamethasone suppression test.

An unenhanced adrenal-dedicated CT scan showed a lipid-rich 2.0 × 1.0–cm right adrenal nodule ( Fig. 7.1 ). The left adrenal gland appeared normal on CT.