Renal & Adrenal MRI: Characterising Masses
For two organs full of incidental lumps, MRI’s tissue characterisation (fat, blood, enhancement) often makes the call CT can’t, without radiation.
Adrenal: the chemical-shift trick
Most incidental adrenal nodules are benign adenomas rich in intracytoplasmic (microscopic) fat. On chemical-shift MRI, such fat causes signal to drop on opposed-phase compared with in-phase images, confidently diagnosing a lipid-rich adenoma.
Renal masses
- Cysts: MRI characterises complexity and enhancement, applying the Bosniak classification to estimate malignant risk.
- Solid tumours: detecting enhancement (the key sign of a solid neoplasm), and distinguishing angiomyolipoma (macroscopic fat) from renal cell carcinoma.
- Staging: venous (renal vein/IVC) tumour thrombus; MRI maps its extent for surgery.
When MRI over CT
MRI is preferred when iodinated contrast or radiation is best avoided (renal impairment, pregnancy, young patients, repeated surveillance), for problem-solving indeterminate CT findings, and for enhancement assessment via subtraction when a lesion is intrinsically high signal.
Sources
- Silverman SG et al. Bosniak classification of cystic renal masses, version 2019. Radiology 2019;292:475–88.
Educational summary for clinicians; correlate with biochemistry and MDT. Not medical advice.