Idiopathic Retroperitoneal Fibrosis: Long-term Risk and Predictors of Relapse.

Rationale & Objective: Idiopathic retroperitoneal fibrosis (IRF) is a rare disorder of unknown cause. Medical therapy can induce remission, but disease relapses are common. This study sought to characterize long-term outcomes of IRF and the factors associated with disease recurrences.