IgG4-related retroperitoneal fibrosis (MONDO_0018848) can be described as follows. Retroperitoneal fibrosis (RPF) is characterized by the development of a fibrotic mass surrounding retroperitoneal structures, such as aorta, vena cava, ureters and psoas muscle. Also known as: Ormond disease, Retroperitoneal Fibrosis, idiopathic retroperitoneal fibrosis, retroperitoneal fibrosis.