What is the management approach for an adrenal nodule?

Management of Adrenal Nodules

All adrenal nodules require both imaging characterization and hormonal evaluation regardless of size, with surgical intervention indicated for nodules >4 cm, those with suspicious imaging features, or those demonstrating hormonal hypersecretion. 1

Initial Evaluation

Imaging Assessment

• Non-contrast CT is the first-line imaging modality 1
  • HU < 10: Benign adenoma (0% risk of adrenocortical carcinoma)
  • HU 10-20: Low risk of malignancy
  • HU > 20: Higher risk of malignancy
  • Size > 4 cm: Higher risk of malignancy 2
• Additional imaging options for indeterminate lesions:
  • Contrast-enhanced CT: >60% washout at 15 minutes suggests benign lesion
  • Chemical-shift MRI: Signal intensity loss in opposed-phase images indicates benign adenoma 1

Hormonal Evaluation

All adrenal nodules require complete hormonal evaluation regardless of size 1:

• 1mg overnight dexamethasone suppression test (cortisol ≤50 nmol/L or ≤1.8 μg/dL indicates normal suppression) 3
• Plasma or 24-hour urinary metanephrines (for pheochromocytoma)
• Aldosterone-to-renin ratio (for primary aldosteronism, especially in hypertensive patients)
• Consider sex hormones (DHEA-S, 17-OH-progesterone, androstenedione, testosterone) if adrenocortical carcinoma suspected 1

Management Algorithm

1. Benign Non-functional Adenomas

• For nodules <4 cm with benign imaging features (HU <10):
  • No further follow-up imaging or functional testing required 2, 1
• For nodules ≥4 cm with benign imaging features:
  • Repeat imaging in 6-12 months 2
  • Consider adrenalectomy if growth >5 mm/year 2
  • No further follow-up needed if growth <3 mm/year 2

2. Indeterminate Non-functional Lesions

• Options include:
  • Repeat imaging in 3-6 months 2
  • Consider surgical resection, especially if:
    • Size >4 cm
    • Heterogeneous appearance
    • Irregular margins
    • Evidence of invasion or necrosis 1
• All patients with indeterminate imaging should be discussed in a multidisciplinary team 2, 3

3. Functional Lesions

• Pheochromocytoma: Surgical resection after appropriate alpha-blockade 1
• Cortisol-secreting adenoma (including mild autonomous cortisol secretion):
  • Surgical treatment should be considered, especially with cortisol-related comorbidities (hypertension, diabetes, osteoporosis) 1, 3
• Aldosterone-producing adenoma: Adrenalectomy for unilateral aldosterone production 1

4. Suspicious for Malignancy

• Surgical resection indicated for:
  • Size >4 cm
  • Irregular margins
  • Heterogeneity
  • HU >20
  • Local invasion
  • Growth on follow-up imaging 2, 1
• Surgical approach:
  • Laparoscopic adrenalectomy: Preferred for benign-appearing tumors <6 cm 1
  • Open adrenalectomy: For tumors >6 cm, irregular margins, local invasion, or suspected malignancy 1, 3

Special Considerations

Bilateral Adrenal Nodules

• Each lesion should be separately characterized using the same criteria as unilateral nodules
• Consider congenital adrenal hyperplasia (measure serum 17-hydroxyprogesterone)
• Assess for adrenal insufficiency in suspected cases of bilateral infiltrative disease, metastases, or hemorrhage 2, 1

Young Adults, Children, and Pregnant Patients

• Require expedited evaluation due to higher risk of malignancy
• Consider MRI instead of CT to reduce radiation exposure 1

Follow-up Recommendations

For Non-operated Patients

• Benign, non-functional nodules <4 cm: No follow-up required 2, 1
• Benign, non-functional nodules ≥4 cm: Repeat imaging in 6-12 months 2
• Indeterminate nodules: Repeat imaging in 3-6 months 2, 1
• Mild autonomous cortisol secretion: Annual screening for cortisol-related comorbidities 3

Post-surgical Follow-up

• Clinical, imaging, and biochemical screening for at least 10 years for patients with adrenocortical carcinoma 1

Potential Pitfalls

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

The management of adrenal nodules requires a systematic approach focusing on imaging characteristics, hormonal evaluation, and size to determine the appropriate treatment strategy and follow-up plan.