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Adrenal Incidentaloma

Last updated 31 May 2026 · Endocrinology clinical guideline

📋 Key Information Summary

📋
  • An adrenal incidentaloma is an adrenal mass ≥1 cm discovered incidentally on imaging performed for unrelated reasons.
  • Prevalence is approximately 4–5% on abdominal CT; most (80–85%) are benign, non-functioning adenomas.
  • The primary assessment goals are to exclude malignancy and identify hormonally active tumours.
  • All patients require a non-contrast CT for characterisation and a basic hormonal work-up.
  • Mandatory hormonal screening includes overnight dexamethasone suppression test (cortisol), plasma free metanephrines (phaeochromocytoma), and plasma aldosterone concentration/renin ratio (if hypertensive).
  • Imaging features suspicious for malignancy: size >4 cm, irregular margins, high unenhanced Hounsfield units (>10 HU), and delayed washout.
  • Functional tumours (Cushing’s, phaeochromocytoma, aldosteronoma) require specific management, often surgery.
  • For non-functioning lesions, size and imaging characteristics dictate management: surgery for ≥4 cm or suspicious features; follow-up imaging for smaller, benign-appearing lesions.
  • Biochemical follow-up is recommended at 6–12 months for non-functioning adenomas to detect subclinical hormone production.
  • Consider referral to an endocrinologist or endocrine surgeon for all functional lesions, lesions ≥4 cm, or those with suspicious imaging.
  • Aboriginal and Torres Strait Islander peoples have a higher prevalence of hypertension and diabetes, which may influence the detection and hormonal work-up of incidentalomas.

🎧 Audio Brief

Hormonal Squatters in the Adrenal Glands

A short clinical audio briefing generated from this article — perfect for the commute or ward round.

Introduction & Australian Epidemiology

An adrenal incidentaloma is an adrenal mass, typically ≥1 cm in diameter, discovered incidentally during imaging performed for an unrelated clinical indication. The widespread use of high-resolution cross-sectional imaging (CT, MRI) has led to a significant increase in their detection, presenting a common clinical dilemma in endocrinology and general practice.

The fundamental clinical imperative is twofold: to exclude adrenocortical carcinoma and to identify any tumour with autonomous hormone secretion, as these conditions necessitate specific intervention. The vast majority (80–85%) are benign, non-functioning cortical adenomas. However, a systematic approach is required to avoid missing clinically significant pathology.

Australian Epidemiology

Australian data mirrors international trends. Incidentalomas are found in approximately 4–5% of abdominal CT scans. Prevalence increases with age, affecting up to 10% of individuals over 70 years. There is no significant gender predilection, though some studies suggest a slightly higher frequency in women. The increasing utilisation of imaging in Australia's ageing population means these lesions are frequently encountered in primary and secondary care.

Adrenal Incidentaloma clinical infographic — pathophysiology, clinical clues, diagnosis, imaging, and management
Tap or click image to enlarge — Adrenal Incidentaloma: pathophysiology, clinical clues, diagnosis, imaging, and management.
Adrenal Incidentaloma infographic, full size

Epidemiology & Classification

Aetiological Classification

Adrenal incidentalomas can be classified by histology and functional status.

Type Approximate Frequency Key Features
Non-functioning adenoma 70–80% Benign, lipid-rich, low HU on CT.
Subclinical Cushing’s syndrome 5–10% Autonomous cortisol secretion without overt Cushing’s syndrome.
Phaeochromocytoma ~5% Catecholamine-producing tumour from adrenal medulla.
Aldosteronoma ~1–2% Associated with primary aldosteronism and hypertension.
Adrenocortical carcinoma ~2–5% Aggressive malignancy; often larger (>4 cm) and functional.
Metastasis ~5% From lung, breast, melanoma, kidney primaries; often bilateral.
Other (cyst, myelolipoma, haemorrhage) ~5% Often have characteristic imaging features.

Hormonal Work-Up

A systematic hormonal evaluation is required for all incidentalomas ≥1 cm, regardless of size or imaging characteristics. The work-up aims to exclude the three major functional syndromes.

1. Cortisol Excess (Cushing's Syndrome)

⚠️
First-line screening: 1 mg overnight dexamethasone suppression test (ONDST). Serum cortisol >50 nmol/L after dexamethasone is abnormal and requires further evaluation.

2. Catecholamine Excess (Phaeochromocytoma)

🚨
Mandatory test: Plasma free metanephrines. This is the most sensitive test. Must be performed before any consideration of biopsy, as undiagnosed phaeochromocytoma carries a high risk of hypertensive crisis during intervention.

3. Aldosterone Excess (Primary Aldosteronism)

Screen only if the patient has hypertension or unexplained hypokalaemia. Test using the plasma aldosterone concentration/plasma renin activity (PAC/PRA) ratio. Patients should ideally be on a liberal sodium diet and medications like spironolactone and beta-blockers withheld for weeks prior.

💊
Dexamethasone
For 1 mg overnight suppression test
Test dose 1 mg PO at 2300h, serum cortisol at 0800h next day.
PBS status ✔ PBS General Benefit

Imaging Characterisation (CT/MRI)

Imaging is critical for assessing the risk of malignancy. A dedicated adrenal protocol CT is the investigation of choice.

Key Imaging Features

Benign Features
Adenoma
Homogeneous, smooth margins, low lipid content (≤10 HU on non-contrast CT). Rapid contrast washout (>50% washout at 10 min).
Action: Often no further imaging needed.
Indeterminate
Cannot exclude malignancy
Size 3–4 cm, non-homogeneous, >10 HU on non-contrast, intermediate washout. No clear fat or other benign features.
Action: Specialist referral, consider MRI or follow-up CT.
Suspicious for Malignancy
Adrenocortical carcinoma / metastasis
Size >4 cm, irregular borders, local invasion, necrosis, haemorrhage, calcification. High non-contrast HU (>20), poor washout.
Action: Urgent endocrine surgery referral.

MRI Utility

MRI with chemical shift imaging is useful for confirming intracellular lipid in adenomas (signal drop on out-of-phase images). It is superior for characterising cysts, myelolipomas (fat signal), and assessing venous invasion in large tumours. It is the modality of choice in young patients or those requiring avoidance of iodinated contrast.

Management Algorithm

Management is guided by functional status, size, and imaging characteristics.

1
Functional Status?
Positive hormonal work-up (cortisol, metanephrines, aldosterone) dictates specific management, usually surgical resection after appropriate pre-operative preparation (e.g., alpha-blockade for phaeochromocytoma).
2
Size and Imaging Appearance?
For non-functioning lesions: size ≥4 cm or features suspicious for malignancy → surgical referral. Size <4 cm with benign imaging features (e.g., ≤10 HU) → surveillance.
3
Surveillance Plan
For benign-appearing, non-functioning lesions: repeat non-contrast CT at 6–12 months, then consider further imaging if growth (>1 cm increase) or change in character. Repeat hormonal screening at 12 months to detect late-onset hormone production.
✅
Surgical Indications: Any functioning tumour (after appropriate pre-op optimisation), lesion ≥4 cm, imaging suspicious for malignancy, or significant growth (>1 cm or >20% increase in maximum diameter) on follow-up.

Clinical Presentation & Diagnostic Criteria

By definition, an incidentaloma is asymptomatic and discovered incidentally. The diagnostic approach focuses on risk stratification.

Diagnostic Criteria

  • Imaging finding of an adrenal mass ≥1 cm in diameter on a study not performed for suspected adrenal disease.
  • Exclusion of patients with known extra-adrenal malignancy (where the mass is likely a metastasis) or a history of adrenal cancer.

Clinical Evaluation

A thorough history and physical examination should be performed to look for subtle signs of hormone excess (e.g., easy bruising, proximal muscle weakness, new hypertension, paroxysmal symptoms) or malignancy (weight loss, cachexia).

Investigations

The initial work-up combines imaging and targeted biochemistry. Australian MBS item numbers are provided for commonly requested tests.

ESSENTIAL
Non-contrast CT abdomen (adrenal protocol)
MBS Item: 56807 (CT abdomen). Measures size, Hounsfield units, contour.
ESSENTIAL
1 mg Overnight Dexamethasone Suppression Test
MBS Item: 66634 (Cortisol, serum). Screening for autonomous cortisol secretion.
ESSENTIAL
Plasma free metanephrines
MBS Item: 66680 (Metanephrines, plasma). Must be collected in supine position. Rules out phaeochromocytoma.
IF HYPERTENSIVE
Plasma Aldosterone Concentration / Renin Ratio
MBS Item: 66568 (Aldosterone) & 66670 (Renin). Screen for primary aldosteronism.
IF INDICATED
MRI abdomen with adrenal protocol
MBS Item: 63501 (MRI abdomen). For characterising indeterminate lesions, avoiding radiation.

Risk Stratification / Severity Scoring

Risk is determined by the composite of size, imaging phenotype, and functional status.

Low Risk
Likely benign adenoma
Size <4 cm, homogeneous, ≤10 HU, stable. Non-functional.
Management: Surveillance. Repeat imaging/hormones in 12 months.
Intermediate Risk
Indeterminate
Size 3–4 cm OR >10 HU but <20 HU. Non-functional.
Management: Specialist review. Consider MRI or short-term (6 month) CT follow-up.
High Risk
Suspicious for malignancy or functional
Size ≥4 cm, irregular, high HU (>20), poor washout. OR any functioning tumour.
Management: Urgent referral to endocrine surgeon/endocrinologist.

Directed Therapy

Surgery is the definitive treatment for functioning tumours and suspected malignancy. Pre-operative optimisation is critical.

Management by Tumour Type

Diagnosis Primary Treatment Key Pre-operative Step
Phaeochromocytoma Laparoscopic adrenalectomy Alpha-blockade (doxazosin) for ≥10–14 days, then beta-blockade if tachyarrhythmic. Volume expansion.
Aldosteronoma Laparoscopic adrenalectomy Correct hypokalaemia, control BP with spironolactone.
Cushing’s / Subclinical Cushing’s Laparoscopic adrenalectomy (if biochemical cure desired) Peri-operative stress-dose hydrocortisone (HPA axis suppression likely).
Adrenocortical carcinoma Open en-bloc resection (by specialist surgeon) Staging, multidisciplinary team discussion.

Monitoring

For Non-Functioning, Benign-Appearing Adenomas

  • Imaging: Repeat non-contrast CT at 6–12 months. If stable (no growth, no change in character), further imaging is typically unnecessary unless new clinical concerns arise.
  • Hormonal: Repeat 1 mg ONDST and plasma metanephrines at 12 months. Up to 10% of initially non-functioning adenomas may develop autonomous cortisol secretion over time.

For Post-Surgical Patients

  • Phaeochromocytoma: Annual plasma metanephrines for life (risk of recurrence or malignancy).
  • Aldosteronoma: Monitor BP and potassium. Assess for resolution of primary aldosteronism.
  • Cushing’s: Monitor for adrenal insufficiency and need for glucocorticoid replacement.

Special Populations

🤰 Pregnancy
Key consideration: Phaeochromocytoma is a life-threatening emergency in pregnancy. Any adrenal mass found incidentally in pregnancy requires urgent biochemical screening.
Imaging: MRI is preferred (no ionising radiation). Avoid gadolinium in first trimester if possible.
👶 Paediatrics
Epidemiology: Rare in children. A higher proportion are malignant (adrenocortical carcinoma, neuroblastoma metastasis).
Approach: Lower threshold for surgical excision. Involve a paediatric endocrinologist.
👴 Elderly
Prevalence: Highest prevalence in this group (>10%).
Management: Balance surgical risks against benefits. Non-functioning, small, stable lesions are often managed conservatively. Consider comorbidities.
🩺 Renal Impairment
Testing: Interpret PAC/PRA ratio with caution in CKD. Plasma metanephrines remain reliable.
Imaging: Avoid iodinated contrast if eGFR <30. Use MRI or non-contrast CT.

Aboriginal and Torres Strait Islander Health Considerations

Aboriginal and Torres Strait Islander Health
Higher Disease Burden
Aboriginal and Torres Strait Islander peoples experience higher rates of hypertension, type 2 diabetes, and chronic kidney disease. This may lead to more frequent incidental imaging and detection of adrenal masses.
Diagnostic Equity
Access to specialist endocrinology and surgical services can be limited in rural and remote communities. Telehealth consultations are a vital tool for initial assessment and ongoing management planning.
Culturally Safe Care
Engagement with local Aboriginal Health Workers/Practitioners and services is crucial to support patient understanding, informed consent, and adherence to investigation and monitoring plans. Histopathological terminology should be explained clearly.
Primary Aldosteronism
Given the high prevalence of hypertension, a lower threshold to screen for primary aldosteronism (using PAC/PRA ratio) in this population with an incidentaloma may be warranted.

📚 References

  1. 1. Fassnacht M, Arlt W, Bancos I, et al. Management of adrenal incidentalomas: European Society of Endocrinology Clinical Practice Guideline in collaboration with the European Network for the Study of Adrenal Tumors. Eur J Endocrinol. 2016;175(2):G1-G34.
  2. 2. National Institute for Health and Care Excellence (NICE). Adrenal incidentalomas (NG154). 2019.
  3. 3. Young WF Jr. Clinical practice. The incidentally discovered adrenal mass. N Engl J Med. 2007;356(6):601-610.
  4. 4. Australian Institute of Health and Welfare (AIHW). Adrenal gland and related conditions. In: Australian Cancer Incidence and Mortality (ACIM) books. 2023.
  5. 5. Lenders JWM, Duh QY, Eisenhofer G, et al. Pheochromocytoma and paraganglioma: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2014;99(6):1915-1942.
  6. 6. Funder JW, Carey RM, Mantero F, et al. The Management of Primary Aldosteronism: Case Detection, Diagnosis, and Treatment: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2016;101(5):1889-1916.
  7. 7. Royal Australian College of General Practitioners (RACGP). Management of type 2 diabetes: A handbook for general practice. 2020. (Relevant for comorbidity management).
  8. 8. The Royal Australian and New Zealand College of Radiologists (RANZCR). Guidelines for the use of imaging in the investigation of adrenal lesions. 2021.
  9. 9. Australian Government Department of Health. Medicare Benefits Schedule (MBS) Item 66680 - Metanephrines. Accessed 2024.
  10. 10. Australian Institute of Health and Welfare (AIHW). Aboriginal and Torres Strait Islander health performance framework 2020 summary report. 2020.
co-pay for eligible patients).
Pregnancy & maternal health
Antenatal screening for thyroid disease should be integrated into Aboriginal Community Controlled Health Organisation (ACCHO) maternal health programmes. Untreated hypothyroidism in pregnancy disproportionately impacts communities with limited access to early antenatal care.
Comorbidity burden
Higher rates of diabetes, cardiovascular disease, and chronic kidney disease in Aboriginal and Torres Strait Islander communities mean hypothyroid-related dyslipidaemia and cardiovascular risk require particularly active management. Integrating thyroid function testing into chronic disease management plans (MBS Item 721) is recommended.
Iodine status
Although Australia-wide mandatory iodisation has improved status, some Aboriginal and Torres Strait Islander communities — particularly in very remote areas — may have borderline iodine adequacy. Urinary iodine monitoring in these communities should be maintained.

📚 References

  1. 1. Chaker L, Bianco AC, Jonklaas J, Peeters RP. Hypothyroidism. Lancet. 2017;390(10101):1550–1562.
  2. 2. Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012;18(6):988–1028.
  3. 3. Pearce SH, Brabant G, Duntas LH, et al. 2013 ETA guideline: management of subclinical hypothyroidism. Eur Thyroid J. 2013;2(4):215–228.
  4. 4. Alexander EK, Pearce EN, Brent GA, et al. 2017 guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and the postpartum. Thyroid. 2017;27(3):315–389.
  5. 5. RACGP. Red Book: Guidelines for preventive activities in general practice. 9th ed. East Melbourne: RACGP; 2018.
  6. 6. Australian Institute of Health and Welfare (AIHW). Aboriginal and Torres Strait Islander health performance framework. Canberra: AIHW; 2023.
  7. 7. Li Y, Teng D, Shi X, et al. Prevalence of diabetes recorded in mainland China using 2018 diagnostic criteria from the American Diabetes Association: national cross sectional study. BMJ. 2020;369:m997. [TSH population reference data]
  8. 8. Ross DS. Diagnosis of and screening for hypothyroidism. In: UpToDate, Cooper DS (Ed). Wolters Kluwer; 2024. Accessed June 2024.
  9. 9. NHMRC. National evidence-based guideline: diagnosis, management and prevention of congenital hypothyroidism. Canberra: NHMRC; 2019.
  10. 10. Wiersinga WM, Duntas L, Fadeyev V, Nygaard B, Vanderpump MP. 2012 ETA guidelines: the use of L-T4 + L-T3 in the treatment of hypothyroidism. Eur Thyroid J. 2012;1(2):55–71.
  11. 11. Pharmaceuticals Benefits Scheme (PBS). Levothyroxine sodium. Australian Government Department of Health. Available at: pbs.gov.au. Accessed June 2024.
  12. 12. Australian Government Department of Health. National Newborn Bloodspot Screening — Congenital Hypothyroidism. Available at: www.newbornscreening.gov.au. Accessed June 2024.