Pitfalls of Adrenal Washout on CT in the Adult Population: A Pictorial Review.

Adrenal washout CT (AWCT) is a well-established reference standard for differentiating adenomas from non-adenomas and has been widely adopted in clinical practice for over three decades. However, in recent years, studies have demonstrated the low specificity of these washout values in diagnosing adenomas, with the latest 2023 European Society of Endocrinology guidelines noting the low quality of evidence regarding the accuracy of these cutoff values. Phaeochromocytomas are recognised as the classic mimickers of adenomas on AWCT as they exceed conventional washout thresholds. However, radiologists should be familiar with other hypervascular lesions to avoid potential diagnostic pitfalls. These hypervascular entities can pose a diagnostic challenge to radiologists who rely too much on washout values and percentages. In this pictorial essay, a comprehensive range of hypervascular adrenal lesions are illustrated. Incorporating lesion morphology, ancillary features, biochemical markers and the presence of extra-adrenal disease are essential for an accurate diagnosis and for avoiding inappropriate management.