Biochemical assessment

Twenty-four-hour urinary catecholamines and fractionated metanephrines (i.e. metanephrine and normetanephrine measured separately) should be quantified to exclude phaeochromocytoma (see Chapter 8). If the pre-test probability of phaeochromocytoma is high (e.g. a vascular mass with high-attenuation pre-contrast/delayed contrast wash-out, pallor spells or a known germline mutation), plasma free metanephrine and normetanephrine should be measured as this test has a sensitivity of 97–99%. However, it is not very specific (85–89%).

An overnight dexamethasone suppression test (1 mg) should be performed to detect autonomous cortisol secretion. If it is abnormal (i.e. an 8–9 a.m. serum cortisol > 50 nmol/L after overnight dexamethasone), baseline serum ACTH and a 2-day high-dose dexamethasone suppression test are indicated to confirm the autonomy (see Chapter 16).

If the patient is hypertensive, plasma potassium concentration and plasma aldosterone-to-renin activity ratio should be measured to screen for primary hyperaldosteronism. Note that patients with primary hyperaldosteronism may not be hypokalaemic. Patients need to be off spironolactone (for 6 weeks) and off angiotensin-converting enzyme inhibitors and angiotensin receptor blockers (for 2 weeks) prior to this test (see Chapter 7).

Treatment

Indications for surgery

Surgery for an adrenal incidentaloma is recommended in patients with:

adrenal masses greater than 4 cm in diameter or with a suspicious imaging phenotype
phaeochromocytoma
a unilateral aldosterone-secreting mass
Cushing’s syndrome.

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