Adrenal washout

Adrenal washout can be calculated using the density value of an adrenal mass on non-enhanced, portal venous phase and 15 minutes delayed CT scans (density measured in Hounsfield units (HU)). It is primarily used to diagnose adrenal adenoma.

  • absolute washout
    • [(HUportal venous phase) - (HUdelayed)] / [(HUportal venous phase) - (HUnon-enhanced)] x 100
    • >60% washout is highly suggestive of adrenal adenoma
  • relative washout
    • [(HUportal venous phase) - (HUdelayed)] / (HUportal venous phase) x 100
    • >40% washout is highly suggestive of adrenal adenoma

Phaeochromocytomas may also wash out, but should have a different clinical presentation. They also may have a higher absolute attenuation on the contrast phase (arterial or portal venous) and any adrenal lesion >120 HU with washout should not be diagnosed as an adenoma.

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rID: 34779
Section: Approach
Synonyms or Alternate Spellings:
  • Adrenal washout calculation

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