Work-Up of Adrenal Incidentalomas  

( The 2021 American Urological Association (AUA) Summer School series included a session on the Evaluation and Management of Adrenal Masses moderated by Dr. Neal E. Rowe, and a presentation by Dr. Thomas McGregor discussing the work-up of adrenal incidentalomas. Dr. McGregor started by highlighting a case presentation of a 58-year-old woman who presented with a UTI and colicky flank pain. A CT scan was ordered to rule out nephrolithiasis, which showed an incidental finding of a 1.7 cm left adrenal lesion:

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The definition of an adrenal incidentaloma is an adrenal mass at least 1cm in diameter that is discovered during imaging for another indication. The prevalence of adrenal incidentalomas has been estimated at 0.4-4.4%, with a higher prevalence in elderly, obese, diabetic, and hypertensive patients. Additionally, there is a higher incidence of adrenal incidentalomas with age, estimated at 7% in patients over the age of 70 years. Of all adrenal incidentalomas, 10-15% are bilateral.

The differential diagnosis of an adrenal incidentaloma depends on several factors, including unilateral versus bilateral, as well as imaging characteristics. It is also important to delineate whether the adrenal mass is functional versus non-functional: 90% of adrenal incidentalomas are benign and non-functional. As follows is a table highlighting the function, symptoms, and screening labs for adrenal masses:

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Approximately 2-5% of adrenal incidentalomas will be malignant, with an increased risk of malignancy over 4 cm in diameter (93% sensitivity, 76% specificity). Additional imaging characteristics that may be helpful including the lipid content, attenuation of CT, and contrast uptake and washout. As follows is an algorithm for assessing contrast washout of an adrenal mass:

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The role of biopsy when assessing an adrenal incidentaloma is when it is not feasible to distinguish between benign adenoma and adrenocortical carcinoma. There also may be a role for biopsy if metastatic disease is highly suspected. Importantly, an adrenal biopsy should be considered only after ruling out the presence of a pheochromocytoma. Pheochromocytomas makeup 3% of all adrenal incidentalomas and can be asymptomatic or present with headaches, pallor, sweating, palpitations, and hypertension. Screening for pheochromocytoma includes 24-hour urine fractionated metanephrines and catecholamines, as well as plasma fractionated metanephrines. A pre-operative medical assessment is crucial in the management of pheochromocytomas, ensuring that the patient is hydrated, on a high sodium diet, as well as on an alpha and beta-blocker. Surgically, it is important to respect the tumor (“no-touch technique”), with early vein ligation to prevent anesthesia complications.

Referring back to the aforementioned case, Dr. McGregor notes that the patient had a 24-hour urine cortisol test, 24-hour urine metanephrines test, and serum aldosterone-to-renin ratio that were all normal. The optimal frequency for follow-up is unclear, with repeat imaging typically at 6, 12, or 24 months, with less frequent imaging if the adrenal mass is <2 cm and there is no history of malignancy. Repeat hormone evaluation should be undertaken only if the patient becomes symptomatic or annually for four years.

Dr. McGregor concluded his presentation of adrenal incidentalomas with the following adrenal nodule summary algorithm:

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Presented by: Thomas McGregor, MD, FRCSC, Queen’s University, Kingston, Ontario, Canada

Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the AUA2021 May Kick-off Weekend May 21-23.