Workup of Adrenal Adenomas
Adrenal adenomas are common, often discovered incidentally when a scan is performed for another reason — hence the term ‘adrenal incidentaloma.’ While most are benign and non-functioning, some can produce hormones or rarely represent malignant disease. The key to evaluation is determining whether the mass is hormonally active and benign or malignant.
1. Initial Detection
Adrenal adenomas are usually identified on CT or MRI scans performed for unrelated reasons. When a mass is found, the next steps depend on its size, imaging features, and biochemical function.
2. Radiologic Assessment
Imaging plays a crucial role in differentiating benign adenomas from potentially malignant lesions.
CT Features
• Size: Lesions <4 cm are usually benign; >4–6 cm raises concern for malignancy.
• Hounsfield Units (HU): <10 HU on unenhanced CT = lipid-rich adenoma (benign).
• Contrast Washout: >60% absolute or >40% relative washout after 10–15 min is typical of adenomas.
• Margins: Irregular borders or necrosis suggest malignancy.
MRI Features
Chemical shift imaging distinguishes adenomas from metastases using lipid content — adenomas lose signal on out-of-phase sequences.
3. Hormonal Evaluation
Every adrenal incidentaloma warrants a biochemical screen to rule out hormone excess.
• Cortisol Excess: 1 mg Overnight Dexamethasone Suppression Test; cortisol >1.8 µg/dL suggests autonomous secretion.
• Catecholamine Excess: Plasma free metanephrines or 24-hour urinary fractionated metanephrines.
• Aldosterone Excess: If hypertensive or hypokalaemic, test aldosterone-renin ratio (ARR >20 suggests primary aldosteronism).
• Androgen or Oestrogen Excess: Rare; test DHEAS, testosterone, or oestrogen levels if virilisation or feminisation.
4. Integration of Results
Combine imaging and biochemical data to guide management: benign non-functioning lesions <4 cm are observed, whereas large or functional lesions require surgery. Biopsy is contraindicated until pheochromocytoma is excluded.
5. Follow-Up
Repeat imaging at 6–12 months for benign, non-functioning lesions, then again at 24 months. Repeat hormonal testing annually for up to 5 years.
6. Multidisciplinary Approach
Evaluation involves an endocrinologist, radiologist, surgeon, and pathologist to ensure accurate diagnosis and appropriate management.
Conclusion
Most adrenal adenomas are benign and asymptomatic. A structured approach combining imaging, biochemical testing, and clinical assessment ensures safe and effective management. Patients benefit most from review in a specialist endocrine unit.