Wolf, J. Stuart

Purpose: We report the first multicenter, prospective, randomized noninferiority controlled trial of steerable ureteroscopic renal evacuation (SURE) for nephrolithiasis treatment. Materials and Methods: Candidates for laser lithotripsy ≥18 years with ≥1 renal stone ≥7 mm and 7–20 mm stone burden were randomized 1:1 SURE vs ureteroscopy (URS). SURE was performed using the CVAC Aspiration System, a novel steerable irrigation–aspiration catheter. The primary efficacy end point was noninferiority in stone-free rate (SFR) based on zero residual fragments (RFs) 30 days postprocedure on noncontrast computed tomography. Secondary end points were superiority tests, stone clearance (percent stone volume reduction), residual stone volume (RSV), SFR (no RF >2 mm), and SFR (no RF >4 mm) 30 days postprocedure. Results: Of the subjects, 123 were randomized and 101 qualified for efficacy analysis (SURE 46 vs URS 55). Despite randomization, baseline URS stone volume was higher (SURE 485.0 ± 432.5 mm 3 vs URS 713.3 ± 558.5 mm 3 ). The primary noninferiority end point was achieved (SURE SFR 48% vs URS SFR 49%, p = 0.027, −1.3% [90% confidence interval; −18%, 15%]). Stone clearance was significantly higher for SURE vs URS subjects (SURE 96.9 ± 5.6% vs URS 92.9 ± 11.6%, p = 0.036); RSV was significantly lower (SURE 14.3 ± 3 0.9 mm 3 vs URS 70.2 ± 144.9 mm 3 , p = 0.012). SURE stone clearance and RSV were independent of baseline stone volume, but for URS degraded with increasing baseline stone volume. Safety was comparable between groups. Conclusions: SFR for SURE subjects was noninferior compared with URS subjects; stone clearance and RSV were significantly better with SURE, independent of baseline stone volume.

Background: The results of a recent pilot study suggest that steerable ureteroscopic renal evacuation (SURE) is safe and more effective in stone removal than basketing following laser lithotripsy. The objective of this retrospective study was to further assess the safety and efficacy of SURE using the CVAC ® Aspiration System (Calyxo, Inc., Pleasanton, CA) in patients with large stone burdens. Materials and Methods: Patients with a baseline stone burden of ≥10 mm who underwent SURE were identified. Subject demographics, secondary procedures, complications, and stone clearance (defined as percent baseline volume reduction) were evaluated. Subanalyses were performed to explore patients identified as high risk for percutaneous nephrolithotomy (PCNL) because (1) they were on anticoagulation or antiplatelet therapy at the time of procedure or (2) they had limited mobility due to neurologic conditions. Results: Identified patients ( N = 43) had a mean preoperative stone burden of 29 ± 12 mm and mean stone volume of 3092 ± 5002 mm 3 . Approximately one-half of patients ( n = 24, 55.8%) had CT imaging at follow-up, and of those, 8 (33.3%) had no residual stones, 22 (91.7%) had >90% stone clearance, 23 (95.8%) had >80% stone clearance, and 24 (100%) had >60% stone clearance. Stone clearance based on baseline stone burden varied between 93.8% and 98.9%. At baseline, 21 patients were anticipated to require staged ureteroscopy; however, only two of those (9.5%) needed secondary procedures. High-risk patients ( n = 22) were on anticoagulation or antiplatelet therapy ( n = 12) or had neurologic conditions ( n = 10). Stone clearance was 97% among patients in the anticoagulated cohort with postoperative CT imaging and 83% in the neurologic condition cohort. There were no device-related complications and no postoperative admissions. Conclusions: The CVAC Aspiration System is safe and effective for treating large stone burdens, including in high-risk patients, and may decrease the need for PCNL or secondary procedures. ClinicalTrials.gov Identifier: NCT04519294.