Retroperitoneal fibrosis is an uncommon inflammatory disorder, which often has significant clinical ramifications. The symptoms are nonspecific, and the diagnosis is typically made with computed tomography (CT) and/or magnetic resonance imaging. In our patient, the diagnosis was first suggested by sonography and confirmed on CT. This report illustrates the ultrasound and CT appearance of retroperitoneal fibrosis including a review of clinical and imaging findings and a discussion of the etiologies.