Retroperitoneal Fibrosis

Imaging

• Irregular, periaortic soft tissue mass extending from renal vessels to iliac bifurcation

  • Aorta not typically displaced from spine in primary retroperitoneal fibrosis

  • Soft tissue can surround inferior vena cava and medially displace ureters

  • Soft tissue may extend to renal hila and into pelvis

• NECT: Isoattenuating to muscle

• CECT or MR: Enhancement varies with stage of disease

  • Early/active disease: Avid enhancement

  • Late/chronic disease: Minimal to no enhancement

• T1WI: Low signal intensity

• T2WI: Signal intensity varies with stage of disease

  • Early/active disease: High signal intensity

  • Late/chronic disease: Low signal intensity

• Prognosis: Decrease in T2 signal intensity, enhancement or size reflects favorable response to treatment