Idiopathic Retroperitoneal Fibrosis: A Single-Center Romanian Cohort with Long-Term Follow-Up

Abstract Idiopathic retroperitoneal fibrosis (iRPF) is a rare immune-mediated fibroinflammatory disease within the spectrum of chronic periaortitis, frequently complicated by ureteral obstruction and renal involvement. While most published cohorts originate from Western Europe, North America, or East Asia, data from Eastern Europe, including Romania, remain scarce. We describe the clinical presentation, radiologic characteristics, treatment patterns, and long-term outcomes of a Romanian single-center cohort of patients with iRPF. This retrospective observational study included adult patients with iRPF managed at a tertiary referral center in Romania between 2010 and 2024. Diagnosis relied on characteristic findings on contrast-enhanced computed tomography or magnetic resonance imaging and exclusion of secondary causes. Disease extent was classified using the Scheel radiologic classification. Clinical, laboratory, imaging, treatment, and outcome data were extracted from medical charts. Remission was defined as resolution or stabilization of imaging findings combined with normalization or stabilization of renal function and inflammatory markers. Relapse was defined as recurrence of hydronephrosis, increase in retroperitoneal mass size, or disease-attributable symptoms with elevated inflammatory markers after documented remission. Twenty-three patients were included (65% male, median age at diagnosis was 55 years). Ureteral involvement was nearly universal with bilateral hydronephrosis present in 91% of cases, and vascular compression observed in over half of cases. All patients had impaired kidney function at diagnosis, with a median estimated glomerular filtration rate of 24 mL/min/1.73m2. Immunosuppressive therapy was administered to 87% of patients, most commonly systemic glucocorticoids, and 57% required urological intervention. Over a median follow-up of 12.2 years, remission occurred in 70%, relapse in 30%. Among patients with available outcome data, remission was achieved in 100% (5/5) of those receiving prednisone monotherapy and 91% (10/11) of those receiving combination immunosuppressive therapy. Infectious complications were documented in 26%, progression to end-stage kidney disease in 9%, and mortality in 35%. In this Romanian cohort, iRPF was often diagnosed at an advanced stage and associated with considerable long-term morbidity, underscoring the importance of earlier recognition.