In this video lecture, we discuss the imaging appearance of lipid-rich and lipid-poor adrenal adenomas, explain the CT washout calculation, and review the choice of CT vs. MRI for the evaluation of adrenal nodules. Also, we compare the 2017 ACR (American College of Radiologists) Incidental Findings Committee recommendations to the AACE/AAES (American Association of Clinical Endocrinologists and American Association of Endocrine Surgeons) medical guidelines in the evaluation of adrenal incidentalomas.
Key points include:
1) 70% of adrenal adenomas will be lipid-rich with a low-density of 10 or less Hounsfield units (HU) on CT.
2) Adrenal nodules with greater than 60% enhancement washout and greater than 40% relative washout are consistent with adenomas.
3) Using chemical shift, MRI may be helpful in characterizing a mass which is indeterminate on non-contrast CT, particularly if the non-contrast density is less than 20-30 HU.
4) If the non-contrast density of an adrenal nodule is greater than 20-30 HU, MRI should be avoided, as washout CT is typically the test of choice.
5) While the AACE/AAES and ACR follow-up algorithms for adrenal nodules differ in many respects, they agree that surgical resection should be considered for adrenal masses measuring 4 cm or more in size, and that biochemical evaluation should at least be considered for most adrenal masses.
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