Adrenal Incidentaloma Dm
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Direct answer
Size, density and hormonal activity decide the fate of every adrenal incidentaloma — a mass of 1 cm or more found on imaging done for another reason. Every patient gets a 1 mg overnight dexamethasone suppression test to exclude autonomous cortisol secretion; hypertensives or those with suspicious imaging add plasma or urinary metanephrines, and patients with hypertension or hypokalaemia add renin and aldosterone — the "rule of three hormones". Density is read in Hounsfield units on unenhanced CT: a homogeneous lesion under 10 HU is a lipid-rich adenoma needing no further imaging, while over 20 HU demands contrast chemistry, with an absolute washout over 60 per cent typical of adenoma. Surgery is offered for masses of 4 cm or more, growth on surveillance, or any hormonal secretion; smaller non-functioning lesions are followed with imaging and repeated hormonal testing for up to five years.
What you must remember
- Epidemiology: incidentalomas appear in roughly 1–5 per cent of abdominal CT scans (higher with thin-slice protocols) and over 5 per cent of autopsies; malignancy is rare but rises steeply with size.
- Hormonal rule: every incidentally found adrenal mass gets assessed for cortisol (1 mg DST); add catecholamine metabolites and the renin-aldosterone pair guided by blood pressure and imaging — phaeochromocytoma must never be missed before any biopsy or surgery.
- Density ladder: unenhanced CT — under 10 HU lipid-rich adenoma; 10–20 HU indeterminate (washout study); over 20 HU suspicious. Myelolipomas announce themselves with macroscopic fat (−30 to −90 HU) and need nothing further.
- Size logic: under 4 cm and hormonally silent — most are benign adenomas; 4–6 cm individualised; over 6 cm carries a substantial adrenocortical carcinoma risk — surgical consultation regardless of hormone status.
- Growth definition: enlargement of 5 mm or more, or over 20 per cent in stable patients, on follow-up imaging prompts rethinking — 5 mm is chosen because 20 per cent of a small nodule is measurement noise.
- Autonomous cortisol spectrum (2023 ESE language): "possible autonomous cortisol secretion" for post-DST cortisol of 1.8–5.0 μg/dL with normal remainder, "autonomous cortisol secretion" above 5.0 — the latter with comorbid diabetes, hypertension or osteoporosis argues for adrenalectomy.
- Adrenocortical carcinoma flags: size over 6 cm, heterogeneous texture, necrosis, invasion, very high DHEAS (or suppressed), androgen excess with virilisation; Weiss score on histology grades malignancy, and mitotane follows for advanced disease.
- Follow-up template: non-functioning lesions under 4 cm — repeat imaging at 6–12 months (once, per current guidance, non-growing), repeat DST annually for up to five years; a lesion unchanged and silent at that point is discharged.
A decision pathway, one patient at a time
A 56-year-old man has a non-contrast CT for renal colic; a 2.8 cm right adrenal lesion, 6 HU, homogeneous, is reported. Step one — clinical screen: no hypertension, no stigmata of cortisol excess, no paroxysmal symptoms. Step two — the hormone set anyway: 1 mg DST returns cortisol 3.2 μg/dL, ACTH suppressed at 8 pg/mL, metanephrines normal, potassium normal — possible autonomous cortisol secretion. Step three — interrogate the comorbidities: his haemoglobin A1c is 6.9 per cent on one agent, blood pressure 138/86; he is not frankly Cushingoid. Step four — decision: in a fit surgical candidate with cortisol co-secretion plus worsening metabolic phenotype, adrenalectomy is a defensible, guideline-supported offer; conservative care with metabolic optimisation and annual DST is equally defensible — and the viva wants both articulated with the comorbidity argument as the pivot. Step five — if conservative: repeat imaging at twelve months (size and texture), then discharge if unchanged. The contrast case writes the other arm: a 5 cm heterogeneous 28 HU lesion with necrosis in a woman with virilisation — that is adrenocortical carcinoma until proven otherwise, straight to surgical referral without biopsy (biopsy only if the mass is unresectable or metastatic workup is needed, and never before phaeochromocytoma is excluded).
Where students slip
Two slips recur. First, dismissing the "silent" nodule — a fifth to a quarter of incidentalomas harbour autonomous cortisol secretion that measurably worsens diabetes, blood pressure and bone density; the DST is not optional. Second, biopsying an adrenal mass before excluding phaeochromocytoma — a hypertensive crisis on the table is the textbook disaster this rule exists to prevent; biopsy of an adrenal mass is almost never required anyway, since adrenal metastases are diagnosed in context. The subtler miss is the bilateral incidentaloma: work up each axis fully (cortisol, catecholamines, aldosterone, and in bilateral disease consider congenital adrenal hyperplasia, haemorrhage, tuberculosis and infiltrative disease — the last two squarely Indian realities).
Frequently asked questions
Which hormonal tests are ordered for every adrenal incidentaloma?
A 1 mg overnight dexamethasone suppression test for everyone, plus plasma or urinary metanephrines and renin-aldosterone when hypertension, hypokalaemia or suspicious imaging raise the pre-test probability.
What CT features indicate a benign adenoma?
Homogeneous texture with unenhanced attenuation under 10 Hounsfield units, or — after contrast — absolute washout of at least 60 per cent (relative over 40 per cent).
What size threshold drives surgical referral?
Around 4 cm individualised with imaging character, and 6 cm or more referred regardless — adrenocortical carcinoma risk rises steeply with size; growth of 5 mm or more on surveillance carries the same message.
What is autonomous cortisol secretion?
Post-DST cortisol above 5 μg/dL with suppressed ACTH and lack of full Cushing stigmata — adrenalectomy is considered when diabetes, hypertension or osteoporosis coexist and outweigh operative risk.
How long is a non-functioning incidentaloma followed?
With one further CT at 6–12 months to confirm stability, and annual dexamethasone suppression testing for up to five years; an unchanged, silent lesion is then discharged from surveillance.