Flexible Ureteroscopy Combined with Novel Ultra-Flexible Ureteral Access Sheaths for Treating Allium Stent Encrustation: Initial Experience with 15 Cases.

Introduction: Encrustation significantly affects the lifespan of Allium stents. Currently, there is no established treatment for Allium ureteral stent encrustation. This study introduces a method for treating these encrustations using a flexible ureteroscopy (F-URS) combined with a novel ultra-flexible ureteral access sheath (UF-UAS). Methods: We retrospectively analyzed patients treated for Allium stent encrustation with UF-UAS from January 2022 to January 2024. Patients with transplanted kidneys were excluded. The UF-UAS features a 10 cm ultra-flexible distal segment, allowing passive deflection beyond 270° during F-URS. This segment, devoid of wire reinforcement, is made of a silicone composite for optimal pliability. The primary endpoints focused on complications such as damage and migration of the Allium stent. Results: A total of 15 consecutive patients (4 men) underwent the procedure. The cohort included 3, 9, and 3 patients with Allium stents measuring 6, 8, and 10 cm, respectively. Mean preoperative stent dwell time was 19.9 months. Preoperative urine cultures were positive in seven patients. Mean operative time was 33.8 minutes. Three patients (20.0%) required a Double-J stent postoperatively. No instances of Allium stent damage were observed. One patient with ≤2 mm fragments and one patient with 2.1-4 mm fragments within the renal. One patient experienced a 1.5 cm Allium migration one day postoperatively. At 3 months, no Allium migration and increased hydronephrosis were observed. Conclusions: The novel UF-UAS facilitated the effective and safe removal of stones, encrustations, and biofilms from Allium ureteral stents. This method may extend the stent lifespan and reduce the need for stent exchanges.