What is the management approach for an incidentally detected adrenal nodule on a computed tomography (CT) scan?

From the Guidelines

The management approach for an incidentally detected adrenal nodule on a computed tomography (CT) scan should prioritize a focused history and physical examination, followed by a low threshold for multidisciplinary review and hormonal evaluation, as recommended by the most recent guidelines 1.

Key Considerations

• For nodules smaller than 1 cm, no further evaluation is typically needed.
• For nodules 1-4 cm, assessment should focus on determining if the mass is hormonally active or potentially malignant.
• All patients should undergo hormonal evaluation including a 1 mg overnight dexamethasone suppression test to screen for cortisol excess, plasma metanephrines or 24-hour urinary catecholamines for pheochromocytoma, and serum potassium and aldosterone-to-renin ratio for primary aldosteronism if the patient has hypertension.

Imaging Characteristics

• Masses with Hounsfield units ≤10 on unenhanced CT are likely benign adenomas.
• Lesions >4 cm generally warrant surgical removal due to increased malignancy risk.

Follow-up and Management

• For indeterminate masses between 1-4 cm without hormonal activity, follow-up imaging is recommended at 6,12, and 24 months to ensure stability.
• If growth exceeds 0.8-1 cm during follow-up or if hormonal activity develops, surgical consultation is appropriate.
• Adrenalectomy should be considered for patients with unilateral cortisol-secreting adrenal masses and clinically apparent Cushing's syndrome, as well as for patients with unilateral aldosterone-secreting adrenal masses and pheochromocytomas 1.

Decision-Making

• Shared decision-making between patients and their clinicians should be used for the management of indeterminate non-functional adrenal lesions, considering options such as repeat imaging or surgical resection 1.
• The approach should balance the need to identify potentially harmful lesions while avoiding unnecessary procedures for the benign adrenal incidentalomas that constitute the majority of these findings.

From the Research

Management Approach for Incidentally Detected Adrenal Nodules on CT Scan

The management approach for incidentally detected adrenal nodules on a computed tomography (CT) scan involves a structured algorithm based on expert consensus, as outlined by the American College of Radiology incidental adrenal White Paper 2.

• Imaging Characteristics: For nodules less than 4 cm, adrenal computed tomography is the most appropriate test 2.
• Biochemical Testing and Endocrinology Referral: In addition to imaging, biochemical testing and endocrinology referral are warranted to exclude a functioning mass 2.
• CT and MRI Characterization: Unenhanced CT and chemical-shift MRI have high specificity for lipid-rich adenomas, while dual-energy CT provides comparable sensitivity for the diagnosis of lipid-rich adenomas 3.
• Adrenal Washout CT: Multiphase adrenal washout CT can be used to differentiate lipid-poor adenomas from metastases, but is limited for the diagnosis of hypervascular malignancies and pheochromocytoma 3.
• Detection and Characterization of Benign Adrenal Lesions: CT has higher sensitivity for detection of small adrenal tumors and adrenal hyperplasia than MRI, while MRI is an important tool in characterization of adrenal masses that could not be characterized using unenhanced CT 4.

Diagnostic Performance of CT and MRI

The diagnostic performance of CT and MRI in detecting aldosterone-producing adenoma has been compared, with similar performances and good interobserver agreement on both CT and MRI imaging 5.

• Sensitivity and Specificity: The calculated sensitivity and specificity for detecting aldosterone-producing adenoma were 87 and 93% for one observer and 85 and 82% for the other observer on CT, and 83 and 83% for one observer and 92 and 92% for the other observer on MR, respectively 5.
• Receptor Operating Characteristics Curve Analysis: This analysis showed similar performances of both observers in detecting an aldosterone-producing adenoma on CT and MR imaging 5.

Special Considerations

In cases of ACTH-independent Cushing's syndrome with bilateral cortisol-secreting adrenal adenomas, precise recognition and management constitute a challenge to clinicians due to the difficulty of exact location of the functional lesions 6.

• Adrenal Venous Sampling: Adrenal venous sampling adjusted by plasma aldosterone can be a useful technique in diagnosing ACTH-independent Cushing's syndrome with bilateral adrenal adenomas prior to surgery 6.