Retroperitoneal Fibrosis

**Definition:** A slowly progressive condition of unknown etiology, characterized by deposition of fibrous tissue in the retroperitoneal space compressing the ureters, great vessels, bile duct, and other structures. When associated with abdominal aortic aneurysm, it may be called chronic periaortitis or inflammatory perianeurysmal fibrosis.

**Tree numbers:** - C23.550.355.700

**Synonyms:** - Ormond Disease - Ormond's Disease - Idiopathic Retroperitoneal Fibrosis