What are the appropriate next steps in evaluating and managing a patient with adrenal incidentaloma after a contrast‑enhanced CT scan?

Next Steps After Contrast-Enhanced CT for Adrenal Incidentaloma

Complete a comprehensive hormonal workup immediately before any further imaging or surgical decisions, as functional testing is mandatory regardless of imaging characteristics and must exclude life-threatening conditions like pheochromocytoma. 1, 2

Mandatory Hormonal Evaluation (Required for Every Patient)

The following tests must be performed on all patients with adrenal incidentalomas ≥1 cm:

• 1 mg overnight dexamethasone suppression test to screen for autonomous cortisol secretion, with cortisol ≤50 nmol/L (≤1.8 μg/dL) excluding cortisol excess, 51-138 nmol/L suggesting possible mild autonomous cortisol secretion (MACS), and >138 nmol/L confirming autonomous cortisol secretion 2, 3

• Plasma free metanephrines or 24-hour urinary metanephrines to exclude pheochromocytoma—this is absolutely essential before any biopsy or surgical intervention to prevent life-threatening hypertensive crisis 1, 2, 3

• Aldosterone-to-renin ratio if the patient has hypertension and/or hypokalemia, with a ratio >20 ng/dL per ng/mL/hr indicating possible primary aldosteronism 2

Imaging Interpretation and Next Steps

Since the patient already had contrast-enhanced CT, the management pathway depends on the imaging characteristics:

If the lesion measured <10 HU on non-contrast sequences:

• No further imaging is needed regardless of size—these homogeneous lesions are benign lipid-rich adenomas 4, 3
• If the lesion is <4 cm and non-functional, discharge the patient without follow-up 5
• If the lesion is ≥4 cm but <10 HU and non-functional, obtain repeat imaging in 6-12 months 5, 4

If the lesion measured 10-20 HU:

• Order second-line imaging with either washout CT or chemical shift MRI to further characterize the mass 5, 4
• Be aware that approximately one-third of benign adenomas fail to washout in the typical adenoma range (≥60%), and conversely, some malignant masses including adrenocortical carcinoma can demonstrate washout in the adenoma range 1
• Chemical shift MRI is an alternative that detects microscopic fat through signal intensity drop without additional radiation exposure 5, 4

If the lesion measured >20 HU:

• Multidisciplinary review is warranted involving endocrinology, surgery, and radiology 5
• For lesions >4 cm that are inhomogeneous or have HU >20, surgery is usually the management of choice given sufficiently high malignancy risk 3

Size-Based Management Algorithm for Non-Functional Lesions

For lesions <4 cm with benign imaging characteristics:

• No further follow-up imaging or functional testing required 5

For lesions ≥4 cm but radiologically benign (<10 HU):

• Repeat imaging in 6-12 months 5, 4
• If growth is <3 mm/year, no further imaging follow-up is required 5, 4
• If growth is >5 mm/year, repeat functional workup and consider adrenalectomy 5, 1

For indeterminate non-functional lesions:

• Repeat imaging in 3-6 months versus surgical resection using shared decision-making 5, 1

For lesions >6 cm:

• Surgical resection should be strongly considered given higher malignancy risk, regardless of washout characteristics 1

Definitive Surgical Indications

Adrenalectomy is definitively indicated for:

• Confirmed pheochromocytoma 5, 1
• Aldosterone-secreting adenoma with confirmed unilateral production on adrenal vein sampling 5, 1
• Clinically apparent Cushing's syndrome from unilateral cortisol-secreting mass 5
• Lesions with radiological features suspicious for malignancy (>4 cm, inhomogeneous, HU >20) 3
• Minimally invasive surgery should be performed when feasible for functional tumors and suspected adrenocortical carcinomas that can be safely resected without capsule rupture 5, 1

Critical Pitfalls to Avoid

• Never perform adrenal biopsy for routine workup—it is rarely indicated and carries risks including tumor seeding and hemorrhage 1, 2
• Never proceed with any intervention before excluding pheochromocytoma, as undiagnosed pheochromocytoma can cause life-threatening hypertensive crisis during surgery or biopsy 1, 2
• Do not rely solely on washout CT results—approximately one-third of pheochromocytomas washout like adenomas, and about one-third of benign adenomas do not washout in the adenoma range 1

Multidisciplinary Review Threshold

Obtain multidisciplinary review when:

• Imaging is not consistent with a benign lesion 5
• Evidence of hormone hypersecretion is present 5
• The tumor has grown significantly during follow-up imaging 5
• Adrenal surgery is being considered 5