St-Amant M, Knipe H, Khalighinejad P, et al. Adrenal washout. Reference article, Radiopaedia.org (Accessed on 05 Nov 2024) https://doi.org/10.53347/rID-34779
Adrenal washout can be calculated using the density value of an adrenal mass on non-enhanced, portal venous phase and 15-minute delayed CT scans (density measured in Hounsfield units (HU)). It is primarily used to diagnose adrenal adenoma.
>40% washout is highly suggestive of adrenal adenoma
Practical points
adrenal washout has limited use when assessing incidental adrenal nodules <4 cm in size and >10 HU in patients without known malignancy 8
lesions that are inhomogeneous with large areas of necrosis or hemorrhage cannot be characterized by their washout pattern
pheochromocytomas and hypervascular metastases (e.g. renal cell carcinoma, hepatocellular carcinoma) may also washout but should have a different clinical presentation; they also may have a higher absolute attenuation on the contrast phase (arterial or portal venous)
1. Johnson P, Horton K, Fishman E. Adrenal Mass Imaging with Multidetector CT: Pathologic Conditions, Pearls, and Pitfalls. Radiographics. 2009;29(5):1333-51. doi:10.1148/rg.295095027 - Pubmed
2. Patel J, Davenport M, Cohan R, Caoili E. Can Established CT Attenuation and Washout Criteria for Adrenal Adenoma Accurately Exclude Pheochromocytoma? AJR Am J Roentgenol. 2013;201(1):122-7. doi:10.2214/AJR.12.9620 - Pubmed
3. Blake M, Cronin C, Boland G. Adrenal Imaging. AJR Am J Roentgenol. 2010;194(6):1450-60. doi:10.2214/AJR.10.4547 - Pubmed
4. Blake M, Kalra M, Sweeney A et al. Distinguishing Benign from Malignant Adrenal Masses: Multi-Detector Row CT Protocol with 10-Minute Delay. Radiology. 2006;238(2):578-85. doi:10.1148/radiol.2382041514 - Pubmed
5. Northcutt B, Raman S, Long C et al. MDCT of Adrenal Masses: Can Dual-Phase Enhancement Patterns Be Used to Differentiate Adenoma and Pheochromocytoma? AJR Am J Roentgenol. 2013;201(4):834-9. doi:10.2214/AJR.12.9753 - Pubmed
6. Sahdev A, Willatt J, Francis I, Reznek R. The Indeterminate Adrenal Lesion. Cancer Imaging. 2010;10(1):102-13. doi:10.1102/1470-7330.2010.0012 - Pubmed
7. Nandra G, Duxbury O, Patel P, Patel J, Patel N, Vlahos I. Technical and Interpretive Pitfalls in Adrenal Imaging. Radiographics. 2020;40(4):1041-60. doi:10.1148/rg.2020190080 - Pubmed
8. Corwin M, Badawy M, Caoili E et al. Incidental Adrenal Nodules in Patients Without Known Malignancy: Prevalence of Malignancy and Utility of Washout CT for Characterization-A Multiinstitutional Study. AJR Am J Roentgenol. 2022;219(5):804-12. doi:10.2214/AJR.22.27901 - Pubmed