Adrenal incidentaloma (AI) is defined as a clinically unapparent adrenal mass > 1 cm in diameter detected during imaging performed for reasons other than for suspected adrenal disease.
Guidelines do not recommend that incidentally found adrenal lesions < 1cm undergo further investigations unless clinically indicated.
Evaluation of AIs
1 - Structural Evaluation
Essentially perform a noncontrast CT adrenal protocol to look for features of malignancy (size, HU). For lesions with HU > 10, then further imaging is required and there is no consensus on the best option (consider chemical shift MR, FDG PET-CT, SPECT-CT)
| Benign Features | Non-Benign Features |
|---|---|
| Size < 4 cm | Size > 4 cm |
| Houndsfield units < 10 | HU > 10 |
| homogenous density | heterogenous (calcifications, extension, adenopathy) |
| hypervascularity, <50% delayed contrast washout |
2 - Functional Evaluation
- Screen for hypercortisolism and pheochromocytoma in ALL adrenal incidentalomas.
- Hypercortisolism
- 1 mg dexamethasone suppression test (preferred over other tests such as 24h UFC, late night salivary cortisol, 9am plasma cortisol)
- should also have low ACTH +/- low DHEAS to support the diagnosis
- 1 mg dexamethasone suppression test (preferred over other tests such as 24h UFC, late night salivary cortisol, 9am plasma cortisol)
- Pheochromocytoma
- urinary metanephrines
- plasma free metanephrines
- Hypercortisolism
- Screen for hyperaldosteronism (Conn syndrome) only if there is hypertension +/- hypokalemia.
- plasma renin:aldo ratio (PRA)
