Use of Antegrade Reverse-thermosensitive Polymer During Percutaneous Nephrolithotomy to Prevent Fragment Migration: Initial Experience

IntroductionOur objective was to evaluate the feasibility and initial performance of Backstop reverse thermosensitive polymer to prevent antegrade stone fragment migration during percutaneous nephrolithotomy.Technical ConsiderationsBackstop was used during 5 percutaneous nephrolithotomy procedures to prevent stone migration into the ureter. Backstop was placed into the upper ureter under direct vision with a flexible nephroscope or with fluoroscopic guidance. Ultrasonic lithotripsy was then performed. Each patient was evaluated for the following: stone-free rate (postoperative computed tomography), rate of antegrade fragment migration, need for subsequent procedures, and complication rate. The average stone burden was 806 mm2. Backstop was successfully deployed in all cases. Average procedure length was 106 minutes. Three patients were rendered stone free, 1 patient retained 2 1-mm fragments in the kidney, and 1 patient retained multiple fragments in the kidney, distal ureter, and bladder, all of which were <3 mm. No patient required a secondary procedure, and there were no adverse events.ConclusionBackstop appears to be feasible, safe, and easy to use. Backstop should be administered every 45 minutes for longer cases, and warm saline should be used during the case to prevent dissolution. A randomized controlled trial with a larger study population is needed to further evaluate these initial findings.