No specific imaging pattern can help differentiate IgG4-related disease from idiopathic retroperitoneal fibrosis: 18 histologically proven cases.

OBJECTIVES: Retroperitoneal fibrosis (RPF) is a rare disease, with unknown aetiology (idiopathic RPF: iRPF) in two-thirds of cases. A subset of iRPF may be a manifestation of IgG4-related disease (IgG4-RD). Thus, recognition of IgG4-RD-RPF is crucial to optimise patient's care with iRPF. The current study aimed to examine imaging specific patterns, which could help differentiate between IgG4-RD-RPF and iRPF, and thus skip performing biopsies. METHODS: This analysis included patients with iRPF and a retroperitoneal biopsy at the Lille University Hospital, France. We reviewed their baseline characteristics, clinical presentation, biological results and imaging features. Patients were classified in 3 groups according to histopathological characteristics of IgG4-RD as follows: highly suggestive of IgG4-RD, possible IgG4-RD, or non-evocative of IgG4-RD. RESULTS: Of the 18 patients analysed in the study, 4 (22%) patients had highly suggestive IgG4-RD-RPF, 8 (44%) possible IgG4-RD-RPF and 6 (33%) non-evocative IgG4-RD. We found no clinical, biological features nor specific imaging pattern that could help differentiate between the 3 groups. CONCLUSIONS: After ruling out all known causes of RPF, retroperitoneal biopsy is still necessary to ascertain the diagnosis of IgG4-RD-RPF. No specific pattern can be used to distinguish between IgG4-RD-RPF and iRFP.