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Adrenal incidentaloma and phaeochromocytoma
Every incidental adrenal mass raises two questions: does it secrete a hormone, and is it malignant? A non-contrast CT density of 10 Hounsfield units or less indicates a benign adenoma, and a phaeochromocytoma is operated on only after alpha-blockade.
Why it matters in the exam
The finding is very common on CT done for another reason, and the exam tests a systematic work-up. The hormonal work-up includes, for every patient, a 1 mg overnight dexamethasone suppression test to exclude cortisol secretion, plasma or urine metanephrines to exclude phaeochromocytoma when the mass is not clearly benign, and an aldosterone-to-renin ratio in a patient with hypertension or low potassium. A standard trap is biopsy of an adrenal mass before phaeochromocytoma has been excluded — it can trigger a hypertensive crisis.
The work-up for malignancy rests on imaging: a homogeneous mass with a density of 10 units or less on non-contrast CT is a lipid-rich adenoma and needs no further imaging follow-up. A heterogeneous mass, high density, size above 4 cm or growth raise suspicion and are investigated with washout CT, MRI or PET, or are resected. For phaeochromocytoma candidates are asked about pre-operative preparation — alpha-blockade first and only then beta-blockade — and about familial syndromes (MEN2, VHL, NF1, SDH).
Key points
- Two questions: is it secreting, and is it malignant?
- For every patient — 1 mg dexamethasone suppression test; metanephrines when the mass is not clearly benign; aldosterone and renin in hypertension or low potassium.
- Non-contrast CT of 10 HU or less and homogeneous — benign adenoma.
- Above 4 cm, high density or growth — further work-up or surgery.
- Phaeochromocytoma: alpha-blockade for 7–14 days before beta-blockade and before surgery.
Summary table
| Question | Test | Positive result | Action |
|---|---|---|---|
| Cortisol secretion | 1 mg dexamethasone suppression test | Morning cortisol above 1.8 µg/dL (50 nmol/L) | Assess metabolic complications; resect for overt Cushing's syndrome or according to comorbidities |
| Phaeochromocytoma | Plasma or urine metanephrines | Clearly raised values | Alpha-blockade for 7–14 days, then laparoscopic adrenalectomy |
| Aldosteronoma | Aldosterone-to-renin ratio (in hypertension or low potassium) | High ratio and a positive confirmatory test | Adrenal vein sampling before resection |
| Malignancy | Non-contrast CT | Density above 10 HU, heterogeneous, above 4 cm or growing | Washout CT, MRI or PET; surgery if suspicion is real |
| Benign non-functioning mass | Density 10 HU or less, homogeneous | — | No further imaging follow-up |
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Sources
- European Society of Endocrinology and ENSAT clinical practice guideline on the management of adrenal incidentalomas, 2023 — Imaging, hormonal work-up and indications for surgery
- Endocrine Society clinical practice guideline: Pheochromocytoma and Paraganglioma, 2014 — Biochemical testing and pre-operative alpha-blockade
- Sabiston Textbook of Surgery, 21st edition (2022) — The Adrenal Glands
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.