Adrenal scintigraphy in primary aldosteronism. Spironolactone as a cause of incorrect classification between adenoma and hyperplasia.

In primary aldosteronism the type of adrenal lesion was correctly identified in 28 of 40 patients (70%) by standard adrenal scintigraphy. Suppression scintigraphy did not improve the validity of the method. In all patients the diagnosis was confirmed by surgery (unilateral adenoma n = 32; bilateral adrenal hyperplasia n = 11). False classification of the adrenal lesion(s) by standard scintigraphy was mostly due to a bilateral adrenal isotopic uptake in patients with an unilateral aldosteronoma. However, a substantial number of these patients (6 of 11 patients) received long-term spironolactone treatment prior to the examination. Thus, in primary aldosteronism adrenal changes induced by chronic spironolactone administration are probably a major cause for incorrect differentiation between adenoma and hyperplasia by adrenal scintigraphy.