Adrenal washout

Last revised by Lautaro Felipe Meneses Vega on 11 Jul 2023

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.

  • 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

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)

  • any adrenal lesion >120 HU with washout should not be diagnosed as an adenoma 7

See also

Various online calculators are available:

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Cases and figures

  • Case 1: adrenal adenoma
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  • Case 2: adrenal adenoma
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