Introduction: Treatment for the idiopathic ureteral stricture has not yet been established. Recently, efficacy of self-expanding large caliber stent (Allium, Allium LTD, Israel) for ureteral stricture related to surgery, radiation or malignancy was reported. This study aims to investigate the effect of Allium stent on idiopathic ureteral stricture. Methods: From July 2018 and January 2022, 54 patients with 58 renal units were underwent ureteroscopic balloon dilation and placement of Allium stent. All the patients showed hydronephrosis before the stenotic lesion and pain. In all the patients, we used, 12 cm or 20cm length of self-expanding Allium ureteral stent and inserted retrogradely with intraoperative x-ray guidance after dilation of the stricture (Figure 1). The primary outcome was immediate improvement in pain and improvement in hydronephrosis through ultrasound examination at 1 month after the procedure. And the secondary outcome was stricture resolution rates following stent removal. Results: Patients and ureteral stricture characteristics were summarized in Table 1. Of 54 patients, 20cm stent was inserted in 47 patients and 12cm stent was inserted in 7 patients. After median follow-up period of 16.5 months, 39.7 % (23/58) of stents were kept in situ. Median indwelling time was 10months (range 1-37) and stent migration was observed in 8 cases (13.8%). All the patients were immediately free of pain after the procedure, and through ultrasound examination, improvement of hydronephrosis was confirmed in 53 out of 58 renal units. Among the 42 renal units which stent removal was performed, 13 renal units (31.0%) recurred stricture. Logistic analysis showed that stricture length was a significant predicting factor for stent failure (HR 2.75, 95% CI 1.58, 4.79, P < 0.01) Conclusions: Self-expanding allium ureteral stenting showed efficacy in relieving pain and improving hydronephrosis in idiopathic ureter stricture with minimal risk of complication. Overall success rate after stent removal was associated with preoperative stricture lengths. SOURCE OF Funding: None
