Is Preoperative Biochemical Testing for Pheochromocytoma Necessary for All Adrenal Incidentalomas?

This study examined whether imaging phenotypes obtained from computed tomography (CT) can replace biochemical tests to exclude pheochromocytoma among adrenal incidentalomas (AIs) in the preoperative setting. We retrospectively reviewed the medical records of all patients (n=251) who were admitted for operations and underwent adrenal-protocol CT for an incidentally discovered adrenal mass from January 2011 to December 2012. Various imaging phenotypes were assessed for their screening power for pheochromocytoma. Final diagnosis was confirmed by biopsy, biochemical tests, and follow-up CT. Pheochromocytomas showed similar imaging phenotypes as malignancies, but were significantly different from adenomas. Unenhanced attenuation values ≤10Hounsfield units (HU) showed the highest specificity (97%) for excluding pheochromocytoma as a single phenotype. A combination of size ≤3cm, unenhanced attenuation values ≤ 10HU, and absence of suspicious morphology showed 100% specificity for excluding pheochromocytoma. Routine noncontrast CT can be used as a screening tool for pheochromocytoma by combining 3 imaging phenotypes: size ≤3cm, unenhanced attenuation values ≤10 HU, and absence of suspicious morphology, and may substitute for biochemical testing in the preoperative setting.