Background. In primary aldosteronism, high-resolution adrenal computed tomography (CT) increasingly identifies subtle anatomic abnormalities. To interpret the functional significance of adrenal micronodular changes on CT scan, we have reevaluated selective adrenal venous sampling. Methods. Thirty- four patients with primary aldosteronism were selected prospectively for adrenal venous sampling on the basis of CT findings: normal findings or minimal thickening of an adrenal limb (n = 15), unilateral microadenoma (n = 6), bilateral adrenal nodules (n = 9), or atypical unilateral adrenal macroadenoma (n = 4). Results. Both adrenal veins were catheterized in 33 of 34 patients. Six (40%) of 15 patients with normal or minimal adrenal limb thickening had a unilateral source of aldosterone. Six patients with apparent unilateral microadenoma had ipsilateral aldosterone-producing adenomas. Four (44%) of nine patients with bilateral adrenal masses had a unilateral source of aldosterone secretion. Three of four patients with unilateral atypical adrenal macroadenomas had ipsilateral aldosterone-producing adenomas. Conclusions. A unilateral source of aldosterone excess may be found in selected patients with adrenal glands that appear normal or show a minimally expanded adrenal limb on CT scan. Findings on adrenal venous sampling are crucial in determining the source of aldosterone excess in patients with bilateral adrenal masses or atypical-appearing macroadenomas.
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