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Adrenal mass
AbdomenCT / MRI
An incidental or symptomatic adrenal lesion. Unenhanced attenuation, chemical-shift signal loss and enhancement washout separate the common benign adenoma from other entities.
Differential
Adenoma (lipid-rich)
common- •Unenhanced attenuation ≤10 HU
- •Signal drop on opposed-phase chemical-shift MRI
- •Absolute washout >60% / relative >40%
Metastasis
common- •Unenhanced >10 HU with low washout
- •Known primary (lung, breast, melanoma), often bilateral
- •Interval growth
Myelolipoma
less-common- •Macroscopic fat (negative HU) with myeloid tissue
- •India-ink chemical-shift artefact at fat interfaces
Phaeochromocytoma
less-common- •Avid enhancement, markedly T2-bright ("light bulb")
- •Cystic/haemorrhagic change; low washout
- •Catecholamine excess (paroxysmal hypertension)
Adrenal haemorrhage
rare- •High attenuation, non-enhancing, decreases over time
- •Trauma, anticoagulation, sepsis
Adrenocortical carcinoma
rare- •Large (>4–6 cm), heterogeneous with necrosis/calcification
- •Venous invasion; hormone hypersecretion
Key discriminators
- •Unenhanced attenuation (≤10 HU = benign adenoma)
- •Chemical-shift signal drop (intracellular lipid)
- •Absolute/relative enhancement washout
- •Macroscopic fat (myelolipoma)
- •Size and heterogeneity (carcinoma)
Work-up / next steps
- 1.Dedicated adrenal CT protocol (unenhanced + 60 s + 15 min washout)
- 2.Chemical-shift MRI for indeterminate lipid-poor lesions
- 3.Biochemical screen (metanephrines, cortisol, aldosterone) as indicated
- 4.FDG-PET or biopsy for suspected metastasis when it alters management
References
- Boland GW et al. Adrenal imaging. Radiology.
- Radiopaedia: Adrenal mass.
Educational clinical decision support only. This differential does not make a diagnosis, is not a medical device, and must never substitute for interpretation by a qualified radiologist correlated with the full clinical picture and prior imaging.