Daniela Cunha;
University of Iowa Hospitals and Clinics
Malia Zhan;
University of Iowa Hospitals and Clinics
Lillian Lai;
University of Iowa Hospitals and Clinics
Sarah Averill;
University of Iowa Hospitals and Clinics
Mohammad Amarneh;
University of Iowa Hospitals and Clinics
Background
Adrenal lesions are a common incidental finding. While they are often benign, there is a wide range of pathologies including functional or malignant entities that require imaging evaluation to guide appropriate medical and surgical management. Familiarity with pseudolesions can avert unnecessary procedures and lengthy imaging follow-up. In most cases, biochemical-hormonal testing, in combination with imaging with ultrasound (US), computed tomography (CT), magnetic resonance (MR), and more rarely functional radioisotope imaging are adequate to achieve a diagnosis and guide treatment.
Educational Goals / Teaching Points
Review the normal physiology and anatomy of the adrenals in the pediatric and adult populations. Review the pathophysiology of functioning adrenal lesions and associated syndromes, and the role of adrenal vein sampling to guide surgical interventions. Review imaging modalities and protocols for differentiating benign from malignant adrenal lesions including CT, MRI and nuclear medicine. Differentiate classic benign adrenal pathology from potential malignant mimics in radiology, as well as imaging technique and interpretative pitfalls of over reliance on washout calculations and chemical shift imaging. Review uncommon cases of adrenal pathology.
Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
In adults, CT is the initial imaging modality for evaluation of adrenal incidentalomas. A noncontrast CT which shows an adrenal mass attenuation of =10 Hounsfield units (HU) is diagnostic for benign, lipid-rich adrenocortical adenomas (ACA). MRI can also identify lipid-rich ACA, but lipid-poor ACA may require multiphase CT with washout calculations. Endocrine evaluation and biopsy are required when nodules have overlapping features such as heterogeneity or avid enhancement. In infants and young children, adrenal pseudonodules often arise from adjacent structures including gastric, hepatic, splenic, and celiac ganglion. US is the modality of choice for workup adrenal hemorrhage, congenital adrenal hyperplasia (CAH) and neuroblastoma in neonates and infants.
Conclusion
Understanding the typical and atypical imaging appearance of common and uncommon adrenal entities, as well as the potential pitfalls when performing and interpreting adrenal imaging is essential to correctly diagnose benign and malignant conditions.
