From the Guidelines
MRI can diagnose adrenal adenomas, particularly when CT findings are inconclusive or when radiation exposure is a concern, with high sensitivity and specificity using chemical shift imaging. This is based on the most recent evidence from 1, which provides guidelines for the diagnosis, management, and follow-up of incidentally discovered adrenal masses.
Key Points
- MRI is useful for characterizing adrenal masses when CT findings are unclear or when radiation exposure is a concern, such as in pregnant patients or children.
- Benign adrenal adenomas typically show signal loss on chemical shift imaging due to their high lipid content.
- Adenomas generally appear isointense or hypointense on T2-weighted images and show mild enhancement after contrast administration.
- MRI has high sensitivity (85-100%) and specificity (92-100%) for diagnosing lipid-rich adenomas, as supported by studies such as 1 and 1.
- However, CT with contrast and adrenal protocol remains the first-line imaging modality for adrenal masses due to its wider availability, lower cost, and ability to characterize most adenomas based on their low density on non-contrast images.
Recommendations
- For patients with indeterminate adrenal masses on non-contrast CT, second-line imaging with either washout CT or chemical-shift MRI is recommended, as stated in 1.
- Adrenal mass biopsy should not be performed routinely for the work-up of an adrenal incidentaloma, according to 1.
- Patients with adrenal incidentalomas should be screened for autonomous cortisol secretion, primary aldosteronism, and pheochromocytoma, depending on their clinical presentation and imaging findings, as recommended in 1.
Clinical Considerations
- The management of adrenal incidentalomas should involve a multidisciplinary approach, including endocrinologists, surgeons, and radiologists, especially when the imaging is not consistent with a benign lesion or when hormone hypersecretion is suspected, as suggested in 1.
- Shared decision-making between patients and their clinicians is crucial for the management of indeterminate non-functional adrenal lesions, considering options such as repeat imaging or surgical resection, as emphasized in 1.
From the Research
MRI Diagnosis of Adrenal Adenoma
- MRI can be used to diagnose adrenal adenoma, particularly with the use of chemical shift imaging (CSI) 2.
- CSI is useful in distinguishing between benign and malignant lesions, and can help avoid further diagnostic or surgical procedures 2.
- MRI is considered a valid complement to other imaging techniques like CT or PET/CT, and is the first choice of imaging for patients like children or pregnant women 2.
Comparison with Other Imaging Modalities
- CT has higher sensitivity for detection of small adrenal tumors and adrenal hyperplasia than MRI 3.
- MRI is an important tool in characterizing adrenal masses that could not be characterized using unenhanced CT 3.
- Dual-energy CT provides comparable to slightly lower sensitivity for the diagnosis of lipid-rich adenomas, but may improve characterization of lipid-poor adenomas 4.
Imaging Features and Diagnostic Accuracies
- Unenhanced CT and chemical-shift MRI have high specificity for lipid-rich adenomas 4.
- 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 4.
- Adrenal adenoma manifests various imaging features on CT, MRI, and positron emission tomography/CT, and the learning objectives of this review are to describe the imaging findings of adrenocortical adenoma, to compare the sensitivities of different imaging modalities for adenoma characterization, and to introduce differential diagnoses 5.