• Benign
  • Composed of variable amounts of fat, smooth muscle and abnormal blood vessel
  • Occur spontaneously
  • Women in 50s
  • Younger age, multiple in patients with tuberous sclerosis
  • Rare in neurofibromatosis and in adult polycystic kidney disease
  • Consists of thick-walled inelastic blood vessels
  • Risk of hemorrhage higher in lesions larger than 4 cm in diameter
  • USG
    • Depends on proportions of fat, muscle and vascular content, any hemorrhage
    • Circumscribed, highly reflective mass, more echogenic than central sinus fat
    • 30% renal cell carcinomas <3 cm in diameter are highly reflective
    • Posterior shadowing is typical that distinguishes from malignancy
  • CT
    • Fatty mass with areas of tissue density
    • Attenuation of -15 HU is diagnostic
    • Perirenal fat being engulfed by a lesion suggests malignancy
  • Angiography
    • Multiple aneurysms
    • ‘onion layer’ appearance
    • Embolization helps control bleeding tumors and treat large tumors to reduce risk of bleed
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Yamakado, Koichiro, et al. “Renal angiomyolipoma: relationships between tumor size, aneurysm formation, and rupture.” Radiology 225.1 (2002): 78-82.