Retroperitoneal, mesenteric and multifocal fibrosis: review of their aetiopathogenesis. A possible role of adipocytes as in Crohn's disease?

First observed during an autopsy by Simpson in 1867 as a cause of hydronephrosis, retroperitoneal fibrosis became a medical topic after the detailed report of two cases by Ormond in 1948. Initially considered to be chiefly an urological disease, it appeared progressively that it could possibly be a systemic disease because of its occasional association with inflammatory fibrosing processes in other sites of the body or with clinical and biological manifestations of hypersensitivity or autoimmunity. Mesenteric panniculitis and mesenteric fibrosis may occur independently or, occasionally, in association with retroperitoneal fibrosis. One third of the cases of retroperitoneal fibrosis can be attributed to specific causes. That the other cases (idiopathic retroperitoneal fibrosis) could be manifestations of an immunological (systemic) process with vasculitis is generally accepted. The authors present a survey of the various possible morphological aspects of the disease and a review of its aetiopathogenesis. Idiopathic retroperitoneal fibrosis is usually characterized by an overproduction of fibro-inflammatory tissue; however in few cases as well as in mesenteric panniculitis, extensive development of fatty tissue may also occur. The authors suggest that an initial proliferation of adipocytes, considered to account for the fat hyperplasia adjacent to Crohn's ileitis, could also play a role in the pathogenesis of the inflammatory fibrosing process in some cases of mesenteric and retroperitoneal fibrosis.