Role of adrenal imaging in surgical management

Adrenal imaging using radiopharmaceuticals is a functional test that can contribute significantly to surgical management and follow-up of patients with either benign or malignant conditions of the adrenal cortex and medulla. Imaging of the cortex is achieved by iodine-131-labeled iodomethyl nor-cholesterol (NP-59), while adrenal medulla imaging can be successfully accomplished by 131I-metaiodobenzylguanidine (MIBG), which localizes in the adrenergic nerve terminal with norepinephrine. Both tests carry high sensitivity and specificity for functional tumors and hyperplasia, and often better than CT scanning. This article reviews the current status and clinical utility of nuclear imaging of the adrenal cortex in congenital hyperplasia, low renin hypertension and aldosteronism, and Cushing's syndrome. Adrenal medulla imaging is reviewed in light of our experience at the University of Texas M.D. Anderson Cancer Center in pheochromocytoma, neuroblastoma, and other neuroectodermal tumors. Investigation of 131I-MIBG therapy of metastatic tumors of neuroectodermal origin potentially offers a means of at least controlling symptoms of hormonal secretion in these patients.