Predictors of irreversible renal dysfunction in patients with idiopathic retroperitoneal fibrosis.

Objectives: Idiopathic retroperitoneal fibrosis (iRPF) can lead to irreversible kidney damage. This study aimed to investigate predictors of irreversible renal dysfunction in patients with iRPF.

Methods: Eighty-three patients with newly diagnosed iRPF were enrolled between January 2010 and Sep 2022 at Zhongshan Hospital of Fudan University, including 60 in the training set and 23 in the validation set. They were regularly contacted or followed up via outpatient examinations by specialist doctors, who documented their condition and treatment progress. Predictors of irreversible renal dysfunction were identified using univariate and multivariate regression, logistic model, and receiver operating curve analyses.

Results: In the training set, over a median follow-up of 29 months, 16.7% of patients had an estimated glomerular filtration rate (eGFR) of < 60 ml/min/1.73m2 at the last follow-up, and 25% had hydronephrosis or required prolonged double-J stents. A prognostic score was developed by assigning 1, 1, and 2 points for peripheral CD19+ B cells <9.3%, serum creatinine (sCr) ≥120 μmol/l, and no response at 6 months, respectively. A score of ≥ 2 for predicting irreversible renal dysfunction had sensitivity and specificity of 100% and 92%, respectively. In the validation set, 21.7% of patients suffered from irreversible renal dysfunction. The sensitivity and specificity for predicting irreversible renal dysfunction were 100% and 94.4%, respectively.

Conclusions: A prognostic score based on factors including CD19+ B cells <9.3% and sCr ≥120 μmol/l at baseline, and no response at 6 months, is suitable for predicting irreversible renal dysfunction in iRPF.