About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
Key points
- Every adrenal incidentaloma asks two questions: is it malignant and is it hormonally active
- Biochemical screening commonly includes cortisol autonomy and pheochromocytoma testing; aldosteronism testing is added in hypertension or hypokalemia
- Do not biopsy an adrenal mass until pheochromocytoma has been excluded biochemically
- Imaging phenotype matters: size, HU, contrast washout, heterogeneity, growth, and history of extra-adrenal cancer
- Urgent referral is needed for suspicious imaging, large or growing mass, hormone excess, or cancer history
Approach to the Presentation
Adrenal incidentalomas are increasingly found on abdominal CT or MRI. The MCCQE1 approach is systematic: determine whether the finding is truly adrenal, assess imaging risk of malignancy, and screen for clinically important hormone secretion. Pheochromocytoma is the major procedural safety diagnosis because biopsy or surgery without alpha blockade can be catastrophic. Autonomous cortisol secretion can present without classic Cushing features but still increases cardiometabolic risk. Primary aldosteronism should be considered in hypertensive or hypokalemic patients. Canadian Urological Association guidance provides a Canadian framework for diagnosis, management, and follow-up.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Adrenocortical Carcinoma | must-not-miss | Large irregular heterogeneous mass, rapid growth, necrosis, local invasion, weight loss, pain, virilisation or mixed hormone secretion | Adrenal-protocol CT/MRI; suspicious size/HU/washout; endocrine and surgical oncology assessment |
| Pheochromocytoma | must-not-miss | Paroxysmal hypertension, headaches, sweating, palpitations, panic-like attacks, orthostasis; may be silent on imaging | Plasma free metanephrines or 24-hour urinary fractionated metanephrines |
| Metastasis to Adrenal | must-not-miss | Known lung, breast, melanoma, renal, or GI cancer; bilateral lesions possible; constitutional symptoms | Cancer history plus imaging phenotype, PET/CT when appropriate; biopsy only after pheochromocytoma excluded |
| Autonomous Cortisol Secretion | must-not-miss | Hypertension, diabetes, osteoporosis, bruising, proximal weakness, central adiposity, or subtle/no Cushingoid appearance | 1 mg overnight dexamethasone suppression test |
| Primary Aldosteronism from Aldosterone-producing Adenoma | common | Hypertension, hypokalemia, muscle weakness, cramps, resistant hypertension, adrenal nodule | Aldosterone-renin ratio, confirmatory testing, adrenal vein sampling in selected surgical candidates |
| Non-functioning Adrenocortical Adenoma | common | Asymptomatic, homogeneous, lipid-rich lesion, stable over time | Unenhanced CT HU <=10 strongly supports benign adenoma |
| Myelolipoma | less common | Benign fat-containing adrenal lesion, usually incidental; large lesions may bleed or cause discomfort | CT showing macroscopic fat |
| Adrenal Cyst or Haemorrhage | less common | History of trauma, anticoagulation, sepsis, pregnancy, or acute flank pain; may mimic mass | CT/MRI evolution and clinical context |
| Congenital Adrenal Hyperplasia or Bilateral Hyperplasia | rare | Bilateral adrenal enlargement, androgen excess, infertility, early-onset hypertension depending subtype | 17-hydroxyprogesterone or endocrine workup as indicated |
Red Flags & Key History
Symptoms
Known extra-adrenal malignancy with new adrenal lesion
Paroxysmal headaches, sweating, palpitations, panic-like episodes, or labile hypertension
Resistant hypertension or hypertension with hypokalemia
Rapid weight gain, proximal weakness, easy bruising, new diabetes, or fragility fracture
Large, irregular, heterogeneous, growing, or invasive imaging appearance
Flank/abdominal pain, weight loss, fever, or constitutional symptoms
Asymptomatic incidental finding on imaging for unrelated abdominal pain
Signs
Severe or paroxysmal hypertension, orthostatic hypotension, tachycardia
Cushingoid features: facial plethora, dorsocervical fat pad, wide purple striae, proximal myopathy
Hypokalemia signs: weakness, cramps, arrhythmia
Virilisation or feminisation suggesting hormone-secreting malignancy
Bilateral adrenal masses or signs of metastatic disease
Approach to Investigation
First-line
Review original imaging reportSize, HU, homogeneity, borders, washout, growth compared with prior imaging, and whether adrenal-protocol imaging is needed
1 mg overnight dexamethasone suppression testScreens for autonomous cortisol secretion
Plasma free or 24-hour urinary fractionated metanephrinesScreens for pheochromocytoma unless imaging clearly lipid-rich and local pathway states otherwise
Aldosterone-renin ratio if hypertensive or hypokalemicScreen for primary aldosteronism; correct potassium and consider medication effects
Second-line
Adrenal-protocol CT or MRICharacterises indeterminate lesions with HU and washout or chemical shift imaging
DHEA-S, androgens, estradiol, steroid precursorsWhen adrenocortical carcinoma or virilising/feminising tumour suspected
Cancer staging investigationsIf imaging or history suggests metastasis or adrenocortical carcinoma
Specialist
Endocrinology/urology/endocrine surgery referralFunctional tumours, suspicious imaging, large masses, growth, bilateral disease, or cancer history
Adrenal vein samplingFor selected primary aldosteronism patients considered for surgery
Management Principles
Canadian Urological Association guideline: diagnosis, management, and follow-up of adrenal incidentalomas1
Initial workup
- Confirm lesion size and imaging phenotype; compare with prior imaging
- Screen for hormone secretion: cortisol autonomy and pheochromocytoma in most; aldosteronism if hypertensive or hypokalemic
- Do not biopsy until pheochromocytoma is excluded and biopsy would change management
2
When to refer urgently
- Suspicious imaging, large mass, rapid growth, local invasion, functional tumour, bilateral lesions with concern, or known malignancy
- Pheochromocytoma requires alpha blockade before beta blockade or surgery
- Autonomous cortisol secretion warrants cardiometabolic risk management and specialist discussion
3
Follow-up
- Benign lipid-rich non-functioning adenomas may require limited or no follow-up depending size/local pathway
- Indeterminate lesions require interval imaging or specialist-led management
- Treat associated hypertension, diabetes, osteoporosis, and hypokalemia while definitive plan is arranged
Complications & Pitfalls
- Biopsy before metanephrines: This can precipitate catecholamine crisis if the lesion is pheochromocytoma
- Calling it incidental without checking function: Hormone secretion may be clinically subtle
- Ignoring aldosteronism: Resistant hypertension or hypokalemia should trigger aldosterone-renin ratio
- Assuming all cancer patients have metastasis: Pheochromocytoma and adenoma can still occur
- Failure to compare old imaging: Stability over years strongly supports benignity
MCCQE1 Exam Tips
- 1Adrenal incidentaloma = malignancy screen plus hormone screen
- 2Never biopsy an adrenal mass until pheochromocytoma is excluded
- 3Pheochromocytoma triad: episodic headache, sweating, palpitations with hypertension
- 4Hypertension + hypokalemia + adrenal mass = aldosterone-renin ratio
- 5Autonomous cortisol secretion can exist without dramatic Cushingoid appearance
- 6HU <=10 on non-contrast CT strongly suggests lipid-rich adenoma
- 7Use a collaborator frame: endocrinology, radiology, urology/endocrine surgery, and oncology may all be needed
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