Adrenal Nodule Calculator CT

Pre-contrast Hounsfield unit

HU <10 - Benign lipid-rich adenoma. No need to give contrast

60-75 second Post-contrast Hounsfield unit

15 minute Delayed Hounsfield unit

Earlier delays reduce the accuracy

Absolute Washout

100 x (Post-contrast HU - Delayed HU)/ (Post-contrast HU - Pre-contrast HU).
Absolute washout of 60% or higher is consistent with an adenoma.

Relative Washout

100 x (Post-contrast HU - Delayed HU)/ Post-contrast HU
Relative washout of more than 40% is suggestive of adenoma.

References:

Schieda, Nicola, and Evan S. Siegelman. “Update on CT and MRI of Adrenal Nodules.” American Journal of Roentgenology208.6 (2017): 1206-1217.

Suggested Reading:

CT of Adrenal Glands – Articl.net

The information provided is not a substitute for clinical judgment. Confirm the calculations before use. The author makes no claims of the accuracy of information.