Delayed glucocorticoid initiation is associated with lower stent removal rates in IgG4-related retroperitoneal fibrosis: a retrospective study.

IgG4-related retroperitoneal fibrosis (IgG4-related RPF) often causes hydronephrosis requiring ureteral stenting. While glucocorticoid (GC) therapy is generally effective, predictors of successful stent removal remain unestablished. This retrospective study investigated whether the interval from radiological diagnosis to GC initiation predicts stent-free outcomes. Twenty-one patients with IgG4-related RPF requiring ureteral stenting between April 2010 and December 2024 were categorized into stent-free (n = 12) and stent-dependent (n = 9) groups. Baseline serological markers (IgG, IgG4, and C-reactive protein) and renal function did not differ significantly between groups. However, the interval from radiological diagnosis to GC initiation was significantly shorter in the stent-free group compared to the stent-dependent group (median 110.5 vs. 264.0 days; p = 0.028). In the primary analysis, patients were dichotomized at the pre-specified cohort median of the diagnosis-to-GC interval (160 days), and Kaplan-Meier analysis showed that early initiation (≤ 160 days) was associated with a significantly higher stent removal rate (p = 0.031). An exploratory ROC analysis yielded a convergent optimal cutoff of 195 days (AUC 0.79; sensitivity 83%, specificity 78%). Delayed GC initiation may be associated with an increased risk of long-term stent dependence, suggesting the existence of a potential therapeutic window of approximately six months for achieving stent-free status.