Aldosterone-producing microadenoma in a patient with primary aldosteronism.

A 54-year-old patient was found to have an aldosterone-producing microadenoma measuring 2.5 mm in diameter. Although adrenal venography by selective catheterization had failed to demonstrate the tumour, adrenal scintiscan using 131I-19-iodocholesterol accurately localized the functional tumour in the right adrenal gland; a dexamethasone-modified adrenal scintiscan revealed complete suppression of radioactivity in the right adrenal gland. These findings suggest that adrenal scintiscan, together with adrenal vein blood analysis, is capable of detecting a small adenoma before surgery, and that dexamethasone suppression of an adrenal scintiscan does not exclude an adenoma.