What is the management approach for an adrenal nodule?

Management of Adrenal Nodules

The management of adrenal nodules should be guided by size, imaging characteristics, and hormonal functionality, with nodules <4cm with benign features requiring no follow-up, while nodules ≥4cm with benign features should undergo repeat imaging in 6-12 months, and adrenalectomy should be considered for nodules growing >5mm/year. 1, 2

Initial Assessment

Imaging Characterization

• Non-contrast CT is the primary imaging modality to assess Hounsfield Unit (HU) values:

  • HU <10: Indicates benign adenoma (0% risk of adrenocortical carcinoma)
  • HU 10-20: Low risk of malignancy
  • HU >20: Higher risk of malignancy, especially for nodules >4cm 2

• Additional imaging features suggesting malignancy:

  • Irregular margins
  • Heterogeneity
  • Local invasion
  • Size >4cm 1, 2

Hormonal Evaluation

All adrenal nodules require complete hormonal evaluation regardless of imaging characteristics:

1. 1mg overnight dexamethasone suppression test (cut-off value ≤50nmol/L or 1.8µg/dL)
2. Plasma or 24-hour urinary metanephrines
3. Aldosterone-to-renin ratio 2, 3

Management Algorithm

For Non-Functional Adrenal Nodules:

1. Benign-appearing nodules <4cm:

   • No further follow-up imaging or functional testing required 1

2. Benign-appearing nodules ≥4cm:

   • Repeat imaging in 6-12 months
   • If growth <3mm/year: No further imaging or functional testing
   • If growth >5mm/year: Repeat functional work-up and consider adrenalectomy 1

3. Indeterminate non-functional lesions:

   • Management options include repeat imaging in 3-6 months or surgical resection
   • Shared decision-making between patient and clinician is recommended 1, 2

For Functional Adrenal Nodules:

1. Cortisol-producing adenomas:

   • For overt Cushing's syndrome: Surgical resection
   • For mild autonomous cortisol secretion with comorbidities potentially related to cortisol excess: Consider surgical treatment 2, 4

2. Pheochromocytomas:

   • Surgical resection after appropriate alpha-blockade 2, 3

3. Aldosterone-producing adenomas:

   • Surgical resection for confirmed cases 2, 5

For Suspicious/Malignant Nodules:

1. Adrenocortical carcinoma (suspected):

   • Surgical resection
   • Open adrenalectomy recommended for tumors >6cm, tumors with irregular margins or local invasion 1, 2

2. Metastatic disease:

   • Management depends on primary cancer and overall disease status 2

Special Considerations

Bilateral Adrenal Incidentalomas

• Each lesion should be separately characterized using the same criteria as unilateral nodules
• Consider measuring serum 17-hydroxyprogesterone to exclude congenital adrenal hyperplasia
• Assess for adrenal insufficiency in suspected cases of bilateral infiltrative disease, metastases, or hemorrhage 1

Pediatric, Young Adult, and Pregnant Patients

• Expedited evaluation due to higher risk of malignancy
• Consider MRI instead of CT to reduce radiation exposure 1, 2

Common Pitfalls to Avoid

1. Failure to exclude pheochromocytoma before invasive procedures
2. Delaying evaluation of suspicious nodules in young patients
3. Performing unnecessary biopsies (adrenal mass biopsy is rarely indicated)
4. Missing mild autonomous cortisol secretion 2

Follow-up Recommendations

• Benign, non-functional nodules <4cm: No follow-up needed
• Benign, non-functional nodules ≥4cm: Repeat imaging in 6-12 months
• Indeterminate nodules under observation: Repeat imaging in 3-6 months
• Post-surgical patients: Follow-up with clinical, imaging, and biochemical screens for at least 10 years 1, 2

The management approach should be tailored based on the likelihood of malignancy, presence and degree of hormone excess, patient age, general health, and patient preference, with the primary goal of identifying and treating potentially harmful conditions such as adrenocortical carcinoma, pheochromocytoma, and hormone-producing adenomas 1, 2, 4.