Is Biochemical Screening for Pheochromocytoma in Adrenal Incidentalomas Expressing Low Unenhanced Attenuation on Computed Tomography Necessary?

Objective: Pheochromocytomas are characterized by a high attenuation value on unenhanced computed tomography (CT). It is not known whether pheochromocytoma could be ruled out as a cause of adrenal incidentalomas on the basis of unenhanced attenuation values only. Design: We retrospectively evaluated the outcome of routine biochemical screening for pheochromocytoma in a series of adrenal incidentalomas in relationship to the unenhanced attenuation values on CT. Methods: An unenhanced CT was available in 174 of 184 patients with 214 adrenal incidentalomas. All patients were screened for pheochromocytoma with 24-h urinary metanephrines and normetanephrines and for hypercortisolism (1 mg dexamethasone test and ACTH). Hypertensive patients were screened for aldosterone overproduction (aldosterone to renin ratio and 24 h urinary aldosterone). The results were compared between incidentalomas with high [≥10 Hounsfield units (HU)] and low (