What imaging study is typically used first to evaluate an adrenal incidentaloma?

What imaging study is typically used first to evaluate an adrenal incidentaloma?

• A. MRI of the brain
• B. Ultrasound of the abdomen
• C. Noncontrast CT of the abdomen
• D. Contrast-enhanced CT abdomen

Answer: (C)

The first imaging step is noncontrast CT of the abdomen. This test quickly measures how much the lesion density attenuates in Hounsfield units. Adrenal adenomas, which are usually lipid-rich, show low attenuation (often less than 10 HU), allowing confident short-circuiting of further workup for many benign cases. If the noncontrast CT shows higher attenuation, additional characterization with contrast-enhanced CT (often using washout calculations) or MRI with chemical-shift imaging is used to distinguish benign from malignant lesions. Ultrasound isn’t reliable for adrenal lesion characterization, and brain MRI isn’t appropriate for this purpose, making noncontrast CT the typical initial study.

The first imaging step is noncontrast CT of the abdomen. This test quickly measures how much the lesion density attenuates in Hounsfield units. Adrenal adenomas, which are usually lipid-rich, show low attenuation (often less than 10 HU), allowing confident short-circuiting of further workup for many benign cases. If the noncontrast CT shows higher attenuation, additional characterization with contrast-enhanced CT (often using washout calculations) or MRI with chemical-shift imaging is used to distinguish benign from malignant lesions. Ultrasound isn’t reliable for adrenal lesion characterization, and brain MRI isn’t appropriate for this purpose, making noncontrast CT the typical initial study.