Is MRI of the brain without contrast adequate for patients suspected of adrenal adenoma, especially those with sensitivity to contrast (Computed Tomography, CT)?

MRI of the Brain Without Contrast is Not Appropriate for Adrenal Adenoma Evaluation

MRI of the brain without contrast is not appropriate for patients suspected of adrenal adenoma, including those with contrast sensitivity. 1 Instead, abdominal imaging focused on the adrenal glands is required for proper evaluation.

Appropriate Imaging for Adrenal Adenoma

First-Line Imaging Options

• CT abdomen without contrast is the most appropriate initial imaging study for suspected adrenal adenoma, with an appropriateness rating of 8/9 1
• CT without contrast can effectively characterize adrenal adenomas based on their lipid content, which lowers their attenuation coefficient 1
• Adenomas typically measure <10 Hounsfield Units (HU) on non-contrast CT, providing high specificity for diagnosis 1, 2

Second-Line Options for Indeterminate Lesions

• Chemical shift MRI of the abdomen (not brain) is recommended when non-contrast CT is equivocal (density >10 HU), with an appropriateness rating of 8/9 1
• Chemical shift MRI relies on differentiating lesions by their relative fat content, as malignant lesions have virtually no lipid 1
• CT with delayed contrast enhancement is appropriate for further characterization when non-contrast CT is indeterminate, with an appropriateness rating of 8/9 1

Why Brain MRI is Inappropriate

• Adrenal adenomas are located in the adrenal glands above the kidneys, not in the brain 1
• Brain MRI without contrast is designed to evaluate intracranial pathology and cannot visualize or characterize adrenal lesions 1
• The ACR Appropriateness Criteria specifically recommend abdominal imaging modalities for adrenal mass evaluation 1

Approach for Patients with Contrast Sensitivity

• Non-contrast CT abdomen remains the first-line approach for patients with contrast sensitivity, as it can effectively characterize many adrenal adenomas without requiring contrast 1, 2
• Chemical shift MRI abdomen without contrast can be used as an alternative when CT is contraindicated or inconclusive 1
• For patients with contrast sensitivity who need further characterization beyond non-contrast studies, chemical shift MRI of the abdomen has demonstrated sensitivity of up to 100% for adenoma detection 1, 3

Diagnostic Algorithm for Suspected Adrenal Adenoma

1. Start with non-contrast CT abdomen (first-line) 1

   • If lesion measures <10 HU → likely adenoma
   • If lesion measures >10 HU → proceed to step 2

2. For indeterminate lesions:

   • If contrast is not contraindicated: CT with delayed enhancement (washout protocol) 1
   • If contrast is contraindicated: Chemical shift MRI abdomen 1

3. For still indeterminate lesions:

   • Consider FDG-PET/CT if malignancy is a concern 1, 3
   • Consider adrenal biopsy only when non-invasive options are exhausted 1

Common Pitfalls to Avoid

• Ordering brain imaging for adrenal pathology is inappropriate and delays proper diagnosis 1
• Relying solely on size criteria (>4 cm suggests malignancy) without proper characterization can lead to unnecessary interventions 4, 2
• Failing to consider chemical shift MRI as an alternative for patients with contrast sensitivity 1, 5
• Not recognizing that certain adrenal lesions like lipid-poor adenomas may appear indeterminate on initial non-contrast CT 6, 2