From the Guidelines
The recommended protocol for a non-contrast CT scan of the adrenal glands is to use it as the first-line imaging to distinguish benign lesions from those which require further radiologic investigation, as stated in the 2023 guideline endorsed by the AUA 1.
Key Considerations
- The scan should be performed with the patient in supine position using 2-3mm slice thickness, with images acquired during a single breath-hold to minimize motion artifacts.
- The scan range should extend from the dome of the diaphragm to the level of the iliac crests, ensuring complete coverage of both adrenal glands.
- Technical parameters generally include 120 kVp, automatic tube current modulation (typically 100-300 mAs), and a standard soft tissue reconstruction algorithm.
- No oral or intravenous contrast is administered.
- Patients should fast for 4-6 hours prior to the examination, though water is permitted.
Diagnostic Value
- Non-contrast CT is effective for detecting adrenal masses larger than 5mm and characterizing their density (measured in Hounsfield Units), which helps differentiate benign adenomas (typically <10 HU) from other lesions.
- This protocol is particularly valuable as the initial imaging study for adrenal incidentalomas and for follow-up of known adrenal lesions, as it minimizes radiation exposure while providing essential diagnostic information about adrenal pathology.
Clinical Guidelines
- According to the 2023 guideline, patients found to have an indeterminate incidental adrenal mass should undergo a non-contrast CT as first-line imaging 1.
- The guideline also recommends that patients who continue to have an indeterminate adrenal mass on non-contrast CT should undergo second-line imaging with either washout CT or chemical-shift MRI 1.
From the Research
Adrenal Protocol Without Contrast
The recommended protocol for a non-contrast Computed Tomography (CT) scan of the adrenal glands is as follows:
- The use of non-contrast CT scans is particularly important in patients with a history of allergy to iodinated contrast media 2.
- In patients with primary aldosteronism and a history of iodine contrast medium allergy, carbon dioxide venography and intraprocedural unenhanced CT can be used for adrenal venous sampling (AVS) 3.
- The diagnostic performance of CO2-intraprocedural unenhanced CT-AVS is similar to that of conventional AVS with iodine contrast media 3.
- Non-contrast CT scans can be used to evaluate the preoperative adrenal vein anatomy 3.
- Intraprocedural unenhanced CT can be used to confirm catheter position in the right adrenal gland 3.
Considerations for Contrast Media
- The use of contrast agents should be carefully considered in patients at risk of adverse reactions, and alternative methods such as non-contrast CT scans should be used when possible 4, 5, 6.
- Patients with pre-existing renal impairment are at increased risk of contrast media nephrotoxicity, and measures such as hydration and the use of non-ionic iso-osmolar dimeric or non-ionic low osmolar monomeric contrast media can help reduce this risk 5, 6.
- The diagnosis of "iodine allergy" is potentially dangerous and can lead to uncertainty in clinical management, and a more specific diagnosis of contrast media allergy should be sought 2.