Primary hyperaldosteronism and adrenal incidentaloma: an argument for physiologic testing before adrenalectomy.

OBJECTIVE: To determine the frequency of nonfunctioning adrenal masses in patients with primary hyperaldosteronism.
DESIGN: A case series.
SETTING: A tertiary care hypertension clinic. PATIENTS: Twenty-seven consecutive patients with primary hyperaldosteronism. MEASUREMENTS: Blood pressure, serum electrolytes, supine and upright plasma renin, cortisol and aldosterone levels, selective adrenal vein aldosterone and cortisol levels, adrenal computed tomography (CT) scans and pathology reports.
RESULTS: There was considerable overlap in the clinical features and laboratory investigations for patients with unilateral aldosteronoma and those with bilateral adrenal hyperplasia. Of the 27 patients who had confirmed primary hyperaldosteronism investigated at this centre, 25 had a definitive diagnosis assigned on the basis of postural stimulation tests, adrenal CT scans, and bilateral adrenal vein sampling, surgery or a combination of test results. Of this group, 18 had adrenal masses visualized on CT. However, only 13 of these 18 patients had an adrenal aldosteronoma subsequently proven by selective adrenal vein sampling or surgery, or both; the other 5 patients were found to have bilateral adrenal hyperplasia with nonfunctioning adrenal masses. CT had a sensitivity of 100% for the diagnosis of aldosteronoma, but the specificity was only 58% and the positive predictive value was only 72%. The likelihood ratio for the diagnosis of aldosteronoma in patients with primary hyperaldosteronism and an adrenal mass on CT was only 2.4.
CONCLUSION: Given the poor specificity of CT in patients with primary aldosteronism, full biochemical and physiologic testing should be done before adrenalectomy in patients with suspected adrenal aldosteronoma.