Retroperitoneal fibroses: aetiopathogenesis and taxonomic assessment.

Retroperitoneal fibrosis (RPF) is a chronic retroperitoneal inflammatory process that can entrap the retroperitoneal structures, mainly the ureters and the great vessels. Aetiology, clinical features and diagnostic appearance in several cases are protean. A true idiopathic form is present in any cases of RPF in which no potential aetiologic condition may be identified. The pathogenesis of the idiopathic RPF appears today to be related to IgG4 autoimmune mechanisms ("hyper-IgG4 disease"). Otherwise, RPF in the presence of aortic atheromatous inflammation (atheromatous aortitis), has been included, more than twenty years ago, among the secondary forms, since this condition appears to be elicited by antigen-acting oxidized-LDL and/or ceroid, that are present within the atheromatous plaque. Aetiology of other secondary RPFs refers to medications (drug-induced), infections, traumas, malignancies. Recent advances in imaging techniques (TC, RM, 18F-FDG/PET or hybrid TC/PET), together with laboratory findings (CRP, ESR, IgG, IgG4, autoantibodies, etc), allow to identify the active phases of the inflammatory process. The review focuses on the pathogenetic features of RPFs and some issues concerning their taxonomic assessment.