AB1414 THE LONG-TERM PROGNOSIS OF ANEURYSM FORMATION AND HYDRONEPHROSIS DUE TO IgG4-RELATED PERIAORTITIS/PERIARTERITIS AND RETROPERITONEAL FIBROSIS (IgG4-PA/RPF): A RETROSPECTIVE SINGLE-CENTER STUDY

Background: The long-term prognosis of IgG4-related periaortitis/periarteritis and retroperitoneal fibrosis (IgG4-PA/RPF) has not been clarified. Objectives: To elucidate the prognosis of IgG4-PA/RPF, specifically focused on renal dysfunction due to hydronephrosis, and aneurysm formation that may lead to rupture, surgical intervention, or dilatation. Methods: A retrospective study was conducted on 61 patients diagnosed with IgG4-PA/RPF at our hospital between January 1, 2006 and January 1, 2023. All cases were diagnosed by experts, based on serological and imaging findings, clinical course, and exclusion of other diseases. The change in estimated glomerular filtration rate (eGFR) from the best eGFR within 3 months of treatment intervention to that at 36 months was defined as the renal outcome. Rupture, surgical intervention, or ≥5mm aneurysm dilatation caused by IgG4-related PA/RPF were defined as aneurysmal outcomes. Results: Among the patients, 53 (86.8%) were men, and the average age at onset was 76.3 ± 9.65 years. The median observation period was 4.93 years(interquartile range [IQR]: 3.35–9.72). The abdominal aorta and the iliac arteries were affected in 48 patients (78.6%), which were the most common sites of involvement. Fifty cases (81.9%) were treated with prednisolone (PSL) monotherapy at a median dose of 25.0 mg/day (IQR: 20.0–30.0), and the remaining cases were observed without intervention. No deaths were recorded during the observation period. Fifteen cases (24.5%) showed hydronephrosis, with bilateral involvement in two. In six cases (40.0%), ureteral stents were placed at a median 13 days (IQR: 1.75–35.5) after identification. All stents were removable, and the median duration until removal was 232 days (IQR: 174–316). The median change in eGFR at 36 months was -5.38 ml/min/1.73m2 (IQR: -15.85–5.08) and the median rate of change was -10.5 % (IQR: -24.1–8.18). In cases without hydronephrosis, the changes in eGFR were -10.84 ml/min/1.73m2 (IQR: -20.25–[-3.54]) and -12.67% (-24.4–[-6.21]) respectively, and there was no significant difference compared to cases with hydronephrosis. One patient with hydronephrosis progressed to end-stage kidney disease, which was complicated by the IgG4-related kidney disease. Seventeen aneurysms were detected in 10 cases (16.3%), with multiple formations observed in five cases. Twelve aneurysms (70.5%) were already formed at the time of IgG4-PA/RPF diagnosis, while two new aneurysms appeared more than 5 years after IgG4-PA/RPF diagnosis. Aneurysmal outcomes were observed in seven cases, including one case of aneurysm rupture, two cases of surgical intervention, and four cases of aneurysm dilatation. The incidence rate in all cases was 2.14 per 100 patients-years (/100PY), while it was 19.0/100PY among cases with aneurysms. These outcomes were observed after a median of 53.0 months (IQR: 26.6–76.6). The presence of an aneurysm at the time of diagnosis was the risk factor of these outcomes (HR=39.1; 95% CI: 4.51–338.6), whereas the administration or dosage of PSL was not. Conclusion: Patients with IgG4-PA/RPF may have a relatively high risk of aneurysm rupture, surgical intervention, and dilatation, and these events may occur more than 5 years after the onset. Patients with aneurysm formation at the time of diagnosis require particular attention. The impact on renal function due to hydronephrosis may be manageable with appropriate interventions among these patients. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.