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Imaging algorithm for adrenal incidentaloma, from Campbell's

Biopsy algorithm, from Campbell's

Surveillance algorithm of adrenal adenoma, from Campbell's

Surveillance algorithm of adrenal adenoma, from Maas 2021

Adrenalectomy indications, from Campbell's

How to Workup an Adrenal Incidentaloma

Identification

• Incidental diagnosis of adrenal mass > 1cm without presence of another malignancy
• 20% may be surgical candidates
• Size matters: if < 4cm, 2% are adrenal carcinomas, 4-6cm increases to 6%, 4cm recommended as cutoff for surgical intervention (93% sensitivity and 42% specificity)
• Two questions: is mass metabolically active, and/or is it a malignancy?

Metabolic Workup

• < 10% adenomas are metabolically active
• Every patient should undergo metabolic workup at diagnosis
• Cortisol: assess with low dose dexamethasone suppression test - take 1mg between 11PM-12AM, check cortisol between 8-9AM the following day, normal < 1.8ug/dL, range 1.8-5ug/dL considered "possible autonomous cortisol secretion"
• Catecholamines: either use free fractionated plasma metanephrines (avoid stimulating agents, draw after 20 minutes supine) or 24hr urinary fractionated metanephrines (collect after discarding first morning void)
• Aldosterone: assess with aldosterone/renin ratio drawn 8-10AM, cutoff ARR > 20 and aldosterone level > 15, consider obtaining only if HTN or hypoK
• Sex steroids: not recommended due to rarity of hypersecretion, only recommended if carcinoma is suspected or obvious signs of feminization/virilization - check DHEA, 17-ketosteroids, testosterone (virilization), 17B-estradiol (feminization)

Imaging

• Identification of intracytoplasmic lipid helps differentiate benign adenomas from other causes
• Unenhanced CT: < 10HU has 71% sensitivity (29% are lipid-poor) and > 98% specificity for adrenal adenoma, if < 10HU then no further imaging required, risk for metastasis in setting of prior extra-adrenal malignancy is < 7%
• Contrast CT: if performed for another reason, usually nondiagnostic but may provide more information on general appearance
• Washout CT: adenomas exhibit rapid contrast washout, image at 15-minutes, > 60% washout vs noncontrast (absolute washout) or > 40% washout vs arterial phase (relative washout)
• MRI: less sensitive than CT, preferred for patients < 40 and/or pregnant patients
• Functional imaging (PET/CT): useful if unclear tumor origin, hx extra-adrenal malignancy or potential malignancy
• Interval growth: if > 20% increase or 5mm maximal growth, concerning for malignancy, recommend removal

Biopsy

• Indications: not metabolically active, not clearly benign on imaging, and pathology results would alter management
• Complications: bleeding, pneumo/hemothorax, risk of HTN crisis if pheochromocytoma

Surveillance (based on guideline summary from Maas 2021)

• Imaging: repeat in one year if obviously benign (minimal benefit for repeating sooner), then no further imaging
• Labs: < 2% spontaneously start producing hormones, recommend annual labs for 4-5yr with symptom check at that time
• Malignant transformation: reportedly < 0.2%

Surgery recommendations

• Laparoscopic: ≤ 6cm and no concern for local invasion
• Open: concern for local invasion
• Indeterminate: individualized approach if patient does not fit into above categories

Relevant Physiology and Embryology to Keep in Mind

Adrenal layers (outer to inner)

• Zona Glomerulosa: produces mineralocorticoids, mainly aldosterone, stimulated by angiotensin II
• Zona Fasciculata: produces glucocorticoids, mainly cortisol, stimulated by ACTH
• Zona Reticularis: produces sex steroids (androgens and estrogens), stimulated by ACTH
• Medulla: produces catecholamines, mainly epinephrine, stimulated by sympathetic input

Potential Congenital Abnormalities

• Agenesis: not common, usually develop normally despite renal anomalies, adrenal gland will be discoid in shape due to lack of renal interaction
• Rests: accessory tissue, can be found along path of gonadal descent, most commonly seen as hyperplastic abnormal testis tissue in CAH