Is a biopsy required to classify patients with idiopathic retroperitoneal fibrosis as IgG4-RPF or Non-IgG4-RPF?

Abstract

Objective Our aim was to group cases of idiopathic retroperitoneal fibrosis (IRPF) into those associated with immunoglobulin (Ig) G4-related disease (IgG4-RD) (IgG4-RPF) and those not associated with IgG4-RD (non-IgG4-RPF) and to compare the clinical presentation, laboratory findings, imaging, and treatment methods. Methods A total of 46 patients were included in the study. According to the assessment by two experienced rheumatologists and the IgG4-RPF classification criteria published by the American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) in 2019, 11 patients who were admitted as IgG4-RPF were included in the IgG4-RPF group and 35 patients who were not admitted as IgG4-RPF were included in the non-IgG4-RPF group. The clinical and demographic characteristics, affected sites, laboratory results and treatments were retrospectively evaluated and compared. Results The mean age of our patients was 50.69 (+/- 11.33) in the non-IgG4-RPF group and 55.36 (+/- 7.80) in the IgG4-RPF group and was similar in both groups (p=0.340). The male gender dominated in both groups. Although there was no significant difference between the groups in terms of acute renal failure (p=0.074), this was more frequent in the IgG4-RPF group (81.82%). An increased IgG4 concentration was found in about half (n=6, 54.55%) of the patients in the IgG4-RPF group, while this was present in only 5.71% (n=2) of the patients in the non-IgG4-RPF group (p=0.001). The most commonly used diagnostic imaging modality was computed tomography. Biopsy was performed in almost all patients (n=10, 90.91%) in the IgG4-RPF group and 11 (31.43%) in the non-IgG4-RPF group (p<0.001). Drug treatment alone and drug treatment in combination with interventional treatment were the most commonly used treatment modalities in the non-IgG4-RPF group (n=12, 34.29% for both). In the IgG4-RPF group, the combination of medical and interventional treatment was the most commonly used treatment modality (n=5, 45.45%). No significant difference was found between the two groups in the assessment of treatment success (p>0.05). Conclusion IRPF can present with similar clinical and imaging findings in IgG4-RPF and non-IgG4-RPF groups. Since a similar treatment success can be achieved in both groups with similar therapeutic agents, we believe that a biopsy is not necessary in patients with an uncertain diagnosis of IRPF.