If noncontrast CT is indeterminate for an adrenal incidentaloma, what imaging is typically used next for further characterization?

If noncontrast CT is indeterminate for an adrenal incidentaloma, what imaging is typically used next for further characterization?

• A. MRI of the abdomen or contrast-enhanced CT
• B. Ultrasound of the abdomen
• C. PET scan
• D. Plain X-ray

Answer: (A)

When a noncontrast CT cannot clearly categorize an adrenal incidentaloma, a study that adds tissue characterization is used next. MRI with chemical shift (out-of-phase versus in-phase) imaging is particularly helpful because adenomas typically contain intracellular lipid; this lipid causes a loss of signal on out-of-phase images, helping distinguish a benign adenoma from non-adenomas such as metastasis or pheochromocytoma. If MRI isn’t available or results are still equivocal, a contrast-enhanced CT with washout analysis is commonly used. Benign adenomas often show rapid contrast washout, whereas malignant lesions tend to retain contrast longer. Ultrasound and plain X-ray don’t reliably characterize adrenal masses, and PET is not the standard next step for initial characterization of an incidentally found adrenal lesion.

When a noncontrast CT cannot clearly categorize an adrenal incidentaloma, a study that adds tissue characterization is used next. MRI with chemical shift (out-of-phase versus in-phase) imaging is particularly helpful because adenomas typically contain intracellular lipid; this lipid causes a loss of signal on out-of-phase images, helping distinguish a benign adenoma from non-adenomas such as metastasis or pheochromocytoma. If MRI isn’t available or results are still equivocal, a contrast-enhanced CT with washout analysis is commonly used. Benign adenomas often show rapid contrast washout, whereas malignant lesions tend to retain contrast longer.

Ultrasound and plain X-ray don’t reliably characterize adrenal masses, and PET is not the standard next step for initial characterization of an incidentally found adrenal lesion.