Overview
Definition:
An adrenal incidentaloma is an adrenal mass discovered incidentally during imaging studies performed for unrelated medical conditions
These masses are typically asymptomatic and are found in 1-10% of the general population, with prevalence increasing with age.
Epidemiology:
The prevalence of adrenal incidentalomas ranges from 1% to 10% in autopsy series and abdominal imaging studies, with higher rates (up to 30%) in patients undergoing imaging for conditions like obesity or hypertension
The risk of malignancy is low, estimated at 5-10% of incidentalomas.
Clinical Significance:
While most adrenal incidentalomas are benign and non-functional, they pose a diagnostic challenge due to the potential for underlying malignancy or hormonal hypersecretion
Timely and appropriate evaluation is crucial to prevent adverse outcomes from undiagnosed functional tumors or metastatic disease
Surgical intervention is considered based on specific criteria related to tumor size, imaging characteristics, and hormonal function.
Diagnostic Approach
History Taking:
Detailed history should focus on symptoms suggestive of hormonal hypersecretion: hypertension, palpitations, sweating (Pheochromocytoma)
weight gain, moon facies, striae, proximal muscle weakness (Cushing's syndrome)
hypokalemia, hypertension (Aldosteronoma)
virilization (adrenal carcinoma)
Family history of endocrine tumors or adrenal disease is also important.
Physical Examination:
Focus on signs of hormonal excess: hypertension, tachycardia, pallor (Pheochromocytoma)
moon facies, buffalo hump, central obesity, skin thinning, striae (Cushing's syndrome)
hypokalemia, hypertension (Aldosteronoma)
hirsutism, clitoromegaly, deepening voice (adrenal carcinoma)
Assess for palpable abdominal masses.
Investigations:
Initial workup involves biochemical screening for hormone overproduction: 24-hour urinary fractionated metanephrines and normetanephrines or plasma free metanephrines for Pheochromocytoma
overnight dexamethasone suppression test (DST) for Cushing's syndrome
plasma aldosterone-to-renin ratio (ARR) for Aldosteronoma
Imaging includes non-contrast CT to assess size, density (Hounsfield units), and morphology
contrast-enhanced CT and MRI for better characterization of adrenal lesions
Iodine-131 metaiodobenzylguanidine (MIBG) scintigraphy or Ga-68 DOTATATE PET-CT may be used for specific indications.
Differential Diagnosis:
Differential diagnoses include benign adenomas (adenomatous hyperplasia), pheochromocytoma, adrenocortical carcinoma, metastasis from other primary tumors, adrenal cysts, and myelolipomas
Distinguishing features are size, imaging characteristics (especially lipid content and enhancement patterns), and biochemical profiles
Solid masses with high Hounsfield units (>20-30 HU on non-contrast CT) or significant contrast enhancement are suspicious for malignancy.
Management
Initial Management:
For asymptomatic, non-functional incidentalomas, the primary management is observation with serial imaging and biochemical reassessment
However, prompt workup is initiated for any suspicion of hormonal activity or malignancy.
Medical Management:
Medical management is primarily aimed at controlling symptoms of hormonal hypersecretion
For suspected pheochromocytoma, alpha-blockade (e.g., phenoxybenzamine) followed by beta-blockade is initiated pre-operatively
For Cushing's syndrome, medical therapies like ketoconazole or metyrapone may be used as temporizing measures or in unresectable cases.
Surgical Management:
Surgical intervention (adrenalectomy) is indicated for incidentalomas meeting specific criteria: 1
Tumors > 6 cm in diameter
2
Tumors with imaging features suggestive of malignancy (e.g., irregular margins, heterogeneous enhancement, rapid growth)
3
Functioning tumors (e.g., Pheochromocytoma, Cushing's syndrome, primary hyperaldosteronism)
4
Patients with indeterminate lesions on imaging after further characterization, especially if suspicious for adrenocortical carcinoma
Laparoscopic adrenalectomy is the preferred approach for benign lesions, while open adrenalectomy may be necessary for larger or suspected malignant tumors.
Supportive Care:
Post-operative care includes monitoring for complications like adrenal insufficiency (requiring steroid replacement), bleeding, and infection
For hormonally active tumors, careful management of electrolytes and blood pressure is essential in the perioperative period
Patients with adrenal insufficiency require lifelong glucocorticoid and potentially mineralocorticoid replacement.
Surgical Thresholds
Size Criteria:
Lesions greater than 4 cm are generally considered for surgical evaluation, with a strong recommendation for surgery if the size exceeds 6 cm
Smaller lesions are managed based on other criteria.
Imaging Features:
Suspicious imaging features warranting further evaluation and potential surgery include heterogeneous attenuation on CT (>20 HU on non-contrast), significant contrast enhancement (>15-20 HU at 10 min post-contrast), irregular margins, central necrosis, and rapid growth on serial imaging.
Hormonal Function:
Any incidentaloma demonstrating hormonal hypersecretion (Pheochromocytoma, Cushing's syndrome, or aldosterone-producing adenoma) requires surgical consideration, often irrespective of size, due to associated morbidities
Indeterminate findings on imaging also necessitate further workup and potential surgical resection.
Adrenocortical Carcinoma Suspicion:
Lesions with high Hounsfield units (>30 HU) on non-contrast CT, significant growth over time, or specific imaging patterns suggestive of invasion or metastasis are highly suspicious for adrenocortical carcinoma and generally require surgical resection.
Complications
Early Complications:
Risks associated with adrenalectomy include bleeding, infection, injury to adjacent organs (e.g., spleen, pancreas, kidney), and adrenal insufficiency
Hypertensive crisis can occur perioperatively in patients with undiagnosed pheochromocytoma.
Late Complications:
Long-term complications primarily relate to adrenal insufficiency if steroid replacement is inadequate or if bilateral adrenalectomy is performed
Recurrence of disease (benign or malignant) can occur, necessitating surveillance.
Prevention Strategies:
Thorough preoperative biochemical and imaging assessment is crucial to identify functional tumors or suspicious lesions
Meticulous surgical technique, including careful dissection and hemostasis, minimizes operative risks
Appropriate perioperative medical management, particularly alpha and beta blockade for pheochromocytoma, is vital.
Prognosis
Factors Affecting Prognosis:
Prognosis is generally favorable for benign adenomas and functional tumors successfully treated with adrenalectomy
For adrenocortical carcinoma, prognosis depends on stage, grade, resectability, and response to adjuvant therapy
Size, presence of metastasis, and hormonal activity are key prognostic indicators.
Outcomes:
Benign incidentalomas, if asymptomatic and non-functional, have excellent prognosis with observation
Surgically treated functional tumors usually resolve their hormonal excess
Adrenocortical carcinoma prognosis is more guarded, with a 5-year survival rate typically below 50%, heavily influenced by stage at diagnosis.
Follow Up:
Patients with non-operative management require regular clinical assessment, biochemical screening for hormonal function, and serial imaging (e.g., CT scan annually for the first 1-2 years) to monitor for growth or new functional activity
Post-adrenalectomy follow-up depends on the pathology, with surveillance protocols tailored to the risk of recurrence or metastasis, especially for adrenocortical carcinoma.
Key Points
Exam Focus:
Understand the size and imaging criteria for surgical intervention of adrenal incidentalomas
Differentiate between benign and malignant features on CT
Recognize the hormonal syndromes associated with functional incidentalomas and their preoperative management
Know the indications for adrenalectomy.
Clinical Pearls:
Always consider hormonal evaluation for adrenal masses, even if asymptomatic
A 10-Hounsfield Unit threshold on non-contrast CT can help differentiate lipid-poor adenomas from other lesions
Preoperative blockade for suspected pheochromocytoma is life-saving
Laparoscopic adrenalectomy is preferred for most benign lesions.
Common Mistakes:
Underestimating the risk of malignancy in larger or radiologically suspicious lesions
Failing to perform adequate biochemical screening for hormonal hypersecretion
Delaying surgical referral for lesions meeting size or imaging criteria
Inadequate preoperative management of functional tumors, particularly pheochromocytoma.