Imaging of Adrenal Incidentalomas: Current Status

Should we use CT or MRI for detection and characterization of benign adrenal lesions?

“…13 In patients with a primary extraadrenal neoplasm and no other evidence of distant metastatic disease, characterization of the lesion using noninvasive imaging can reduce the necessity for percutaneous adrenal mass biopsy in most patients. 14 Characterization of lipid-rich adenomas is straightforward using both unenhanced CT and MRI, and represented with attenuation values of ≤10 HU on CT, and obvious signal drop on opposed-phase MRI. 13 Unfortunately, about 29% of adenomas have attenuation values higher than 10 HU and remain indeterminate on unenhanced CT scan.…”

“…Moreover, the assessment of enhancement washout of adrenal masses is valid only for lesions with relatively homogeneous attenuation after contrast administration. 14 To avoid unnecessary use of ionizing radiation, especially in younger patients, adrenal MRI could be of great help in characterization of adrenal masses.…”

Acute adrenal insufficiency due to bilateral adrenal hemorrhage

“…Findings of adrenal hemorrhage include peri-adrenal fat stranding and thickening of adjacent diaphragmatic crura. Also it is characterized by increased volume of the adrenal gland by a round or oval mass and hyper attenuating foci in the range of +50 to +90 HU (7). Differential diagnoses to be considered include leaking aortic aneurysm, bleeding from retroperitoneal organs, renal vein thrombosis, and abdominal abscess.…”

Risk of catecholamine crisis in patients undergoing resection of unsuspected pheochromocytoma

“…Defining typical characteristics of a pheochromocytoma by CT is difficult as heterogeneous enhancement and poor washout as well as FDG uptake on PET may also be seen in a metastasis or adenoma (1,4,11). Further imaging by magnetic resonance (MR) is also problematic, as up to 35% of pheochromocytomas do not exhibit the "lightbulb bright" high T2 signal classically associated with pheochromocytomas (1).…”

“…While there is widespread awareness of the classical clinical and radiological features of pheochromocytoma, it is perhaps less well known that 10% of pheochromocytomas are not associated with symptoms of excess catecholamine production, and up to 35% of pheochromocytomas have atypical imaging findings (1)(2)(3)(4)(5). Accordingly, the diagnosis may be unsuspected, and an indeterminate adrenal or retroperitoneal mass that is actually a pheochromocytoma could undergo resection without preoperative commencement of biochemical blockade.…”