In a patient with bilateral adrenal adenomas presumed benign six years ago and no imaging since, is follow‑up imaging and hormonal evaluation recommended?

Follow-Up of Bilateral Adrenal Adenomas After 6 Years Without Imaging

If the bilateral adrenal adenomas were confirmed as benign on initial imaging (with <10 HU on unenhanced CT) and were <4 cm in size, no further follow-up imaging or hormonal testing is required. However, given the 6-year gap without imaging and the bilateral nature of these lesions, a one-time reassessment is reasonable to confirm stability and exclude interval development of hormonal excess.

Key Decision Points

Size and Imaging Characteristics Matter Most

The 2023 CUA/AUA guidelines provide clear direction: patients with benign non-functional adenomas <4 cm confirmed on initial imaging do not require further follow-up imaging or functional testing 1. This strong recommendation is based on the extremely low malignancy risk in this population.

However, the guidelines also state that patients with non-functional adrenal lesions that are radiologically benign (<10 HU) but ≥4 cm should undergo repeat imaging in 6-12 months 1. The critical threshold is:

• <4 cm and <10 HU: No follow-up needed
• ≥4 cm and <10 HU: Follow-up imaging warranted

The 6-Year Gap Creates Uncertainty

While the guidelines don't specifically address patients who had appropriate initial workup but then had no imaging for 6 years, several considerations apply:

In favor of one-time reassessment:

• The bilateral nature requires each lesion to be characterized separately 1
• A retrospective study of 322 bilateral adrenal nodules in patients without cancer found zero cases of malignancy, suggesting very low risk 2
• However, this same study noted two nodules that grew over long-term follow-up (8-12 years) 2

Against routine follow-up:

• If the original lesions were definitively benign (<10 HU, <4 cm), the guidelines explicitly state no further follow-up is needed 1
• The European Society of Endocrinology 2023 guidelines now state that homogeneous lesions with ≤10 HU on unenhanced CT are benign and do not require additional imaging independent of size 3

Recommended Approach

Step 1: Review Original Imaging Characteristics

Obtain the original imaging report and determine:

• Exact size of each adenoma
• Hounsfield units on unenhanced CT (if performed)
• Whether washout studies or chemical shift MRI confirmed benign adenoma 1

Step 2: Hormonal Screening (Recommended Regardless)

Even if imaging follow-up is not indicated, hormonal screening should be performed because:

• The guidelines recommend screening all adrenal incidentalomas for hormonal excess 1
• Mild autonomous cortisol secretion (MACS) can develop over time and is associated with increased morbidity and mortality 3
• Bilateral lesions require consideration of congenital adrenal hyperplasia and adrenal insufficiency 1

Perform the following tests:

• 1 mg dexamethasone suppression test (cortisol should be ≤50 nmol/L or ≤1.8 µg/dL) 1, 3
• Plasma or 24-hour urinary metanephrines (only if lesions were >10 HU or if symptoms present) 1
• Aldosterone-to-renin ratio if hypertension or hypokalemia present 1
• Consider 17-hydroxyprogesterone for bilateral lesions to exclude congenital adrenal hyperplasia 1

Step 3: Imaging Decision Algorithm

If original lesions were <4 cm and <10 HU:

• No imaging follow-up required per guidelines 1
• However, given 6-year gap, consider one-time repeat CT to document stability and provide reassurance

If original lesions were ≥4 cm (even if <10 HU):

• Repeat imaging is indicated 1
• Use unenhanced CT as first-line modality

If original imaging characteristics are unknown or indeterminate:

• Repeat imaging is necessary to properly characterize the lesions 1

Step 4: Subsequent Follow-Up Based on Findings

If repeat imaging shows:

• Growth <3 mm/year: No further imaging or functional testing required 1
• Growth >5 mm/year: Consider adrenalectomy after repeating functional workup 1
• Stable lesions that remain <10 HU and <4 cm: No further follow-up needed 1

Important Caveats

Bilateral Lesions Require Special Consideration

Each lesion must be evaluated independently as they may have different etiologies 1. The differential diagnosis for bilateral masses is broader and includes metastases (though rare without known primary malignancy), infiltrative disease, and bilateral pheochromocytomas 4.

Age and Clinical Context Matter

The guidelines note that adrenal lesions in young adults are more likely to be malignant, though this patient's lesions were identified 6 years ago and presumed benign 1. If the patient is now older, the risk profile has likely improved.

Pitfall: Assuming All Bilateral Lesions Are the Same

Don't assume both adrenal masses share the same pathology—they require independent characterization 1, 4. One could be a benign adenoma while the other could be a different entity.

Pitfall: Overlooking Hormonal Excess

Approximately 1-30% of adrenal incidentalomas secrete cortisol, and this can develop over time 1. Patients with MACS have increased cardiovascular morbidity and mortality even without overt Cushing's syndrome 3, making hormonal screening essential regardless of imaging stability.

Practical Bottom Line

For a patient with bilateral adrenal adenomas confirmed benign 6 years ago with no interval imaging, perform hormonal screening now and consider one-time repeat imaging if the original lesions were ≥4 cm or if imaging characteristics were not definitively benign (<10 HU). If original lesions were <4 cm and <10 HU, hormonal screening alone is reasonable, though one-time imaging provides reassurance given the prolonged interval 1, 3.