Retroperitoneal fibrosis is a rare immune-mediated disease characterised by a periaortoiliac fibro-inflammatory tissue that often encases neighbouring structures (eg, ureters). Idiopathic retroperitoneal fibrosis can be isolated or part of IgG4-related disease, whereas secondary forms recognise different aetiologies, such as histiocytosis, malignancies, and infections. Idiopathic retroperitoneal fibrosis has a multifactorial origin, with genetic, environmental, and lifestyle factors being main contributors.