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Background
Incidental adrenal nodules are seen in approximately 5-7% of adults and incidence increases with age. A large majority are ultimately found to be benign, sometimes after a workup that includes imaging that is not ideal or timed properly. As radiologists, we recognize there is room for improvement in the management of adrenal nodules to ensure proper and efficacious patient care. The goal of this exhibit is to update learners on adrenal imaging and to provide them with a unique algorithm to easily and efficiently stratify incidental adrenal lesions.

Educational Goals / Teaching Points
The initial history of the patient's symptoms, cancer history, and survey of prior imaging is always the first step in the evaluation of adrenal nodules. Incidental adrenal nodules can be stratified into three large categories we call off-ramp lesions, on-ramp lesions, and fast lane lesions. Those in the off-ramp category are immediately dismissible based on imaging characteristics such as size, density, stability, and the presence of macroscopic fat or calcifications. On-ramp lesions are true incidental findings in patients without symptoms or a history of cancer and usually need at least one follow-up imaging test. Fast lane lesions are nodules in patients with cancer or endocrine abnormalities and are handled differently. After reviewing this exhibit, learners should understand and be able to describe what history is required before applying the incidental adrenal algorithm, list benign imaging characteristics, interpret and define the strengths of a one-year follow-up adrenal protocol CT, and make the most efficacious follow-up recommendations in all patient groups.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Imaging findings of immediately dismissible, truly incidental adrenal nodules are size less than 1 cm in the short axis, Hounsfield units less than 10, stability for at least 1 year, and the presence of macroscopic fat or calcifications. If not dismissible based on imaging features or patient history, biochemical labs and size determine risk stratification and guide management. Adrenal CT is often more informative than adrenal MRI but proper interpretative skills are required to prevent misdiagnosis. Additionally, new imaging techniques are emerging for the evaluation of adrenal nodules such as dual-energy CT and PET/CT.

Conclusion
Adrenal nodules are commonly encountered by all radiologists. It is important to understand the imaging characteristics and how they correlate to risk stratification in order to provide safe and cost-effective patient care. This exhibit gives an up-to-date streamlined algorithm for the evaluation of adrenal nodules. The exhibit also provides updated information on other novel and emerging imaging modalities for adrenal nodule evaluation.