Retroperitoneal fibrosis is the presence of a fibrotic plaque in the prelumbar or presacral area. It can occur as a result of certain medications, fluid collections, inflammatory disease of various intra-abdominal organs, previous surgery or radiation therapy and various metastatic neoplasms. Most cases of retroperitoneal fibrosis are considered idiopathic. We report an interesting case of idiopathic retroperitoneal fibrosis with the emphasis on the importance of pathology to establish the diagnosis.