Adrenal Washout Analysis

ACR 2017ACR

Washout Calculator for Adrenal Lesion Characterization

Calculates absolute and relative washout percentages using HU values measured in pre-contrast, contrast-enhanced, and 15-minute delayed phases of adrenal lesions. The most important CT criterion for adenoma vs malignancy differentiation. Pre-contrast <10 HU alone diagnoses lipid-rich adenoma.

Pre-contrast HU (unenhanced)

Absolute washout (%)

Relative washout (%)

Lesion size

Select all features

References

Mayo-Smith WW, et al. Management of Incidentally Discovered Adrenal Masses: A White Paper of the ACR Incidental Findings Committee. JACR 2017;14(8):1038-1044.
Caoili EM, et al. Adrenal masses: characterization with combined unenhanced and delayed enhanced CT. Radiology 2002;222(3):629-633.
Defined criteria: Defined criteria: Defined criteria: Blake MA, et al. Adrenal Imaging. Cambridge University Press, 2015.

This classification system is intended for clinical decision support. Final diagnosis and treatment decisions rest with the clinician.

Categories

ADENOMAdenoma (Benign)Benign (>98% specificity)

Washout analysis consistent with adenoma — no follow-up needed

Pre-contrast <10 HU (lipid-rich adenoma, no washout needed)
Absolute washout >60%
Relative washout >40%
Chemical shift MR signal drop

Management: No follow-up needed (functional evaluation separate)

BELIRSIZIndeterminateLow-moderate malignancy risk

Washout values below diagnostic thresholds — further workup needed

Pre-contrast 10-30 HU
Absolute washout 40-60%
Relative washout 20-40%
Chemical shift equivocal

Management: MR chemical shift or PET-CT or 6-12 month follow-up CT

SUPHELISuspicious (Malignancy)High malignancy risk

Washout values inconsistent with adenoma — malignancy suspected

Pre-contrast >30 HU
Absolute washout <40%
Relative washout <20%
Large size (>4 cm)
Irregular border, necrosis, invasion

Management: Biopsy or surgery (rule out adrenocortical carcinoma, metastasis, pheochromocytoma)

References

Mayo-Smith WW, et al. Management of Incidentally Discovered Adrenal Masses: A White Paper of the ACR Incidental Findings Committee. JACR 2017;14(8):1038-1044.

Caoili EM, et al. Adrenal masses: characterization with combined unenhanced and delayed enhanced CT. Radiology 2002;222(3):629-633.

Defined criteria: Defined criteria: Defined criteria: Blake MA, et al. Adrenal Imaging. Cambridge University Press, 2015.