Adrenal imaging with 131I-19-iodocholesterol in the diagnostic evaluation of patients with aldosteronism.

The results of adrenal scintiscans, venograms and venous aldosterone levels are compared with the histologic findings in 33 patients submitted to operations for primary aldosteronism. Standard and suppression scintiscans were performed 2-14 days following intravenous administration of 2mCi of 131I-19-iodocholesterol. The adrenal lesions were histologically classified into four categories: 25 patients had adenomas, 6 had macronodular hyperplasia, 1 had microscopic hyperplasia and 1 had an adenocarcinoma. Asymmetrical uptake between the two adrenals seen on standard scintiscans did not differentiate between a tumor or asymmetrical hyperplasia, unless the tumor was greater than 2 cm in diameter. During suppression scintiscans, unilateral uptake visible within five days of tracer injection was consistent with adenoma. Patients with nodular hyperplasia demonstrated early uptake in both adrenal glands during suppression scintiscans, while the patient with microscopic hyperplasia did not. The type of adrenal lesion was correctly identified in 20/26 (77%) of patients by suppression scintiscans; 21/28 (75% of patients by venograms and 12/16 (75%) of patients who had adrenal venous aldosterone measurements attempted. The majority of surgically correctible lesions could be identified on suppression adrenal scintiscans. Adrenal vein catheterization can be reserved for those patients in whom the results of suppression scintiscans are inconsistent with the clinical degree of aldosteronism.