Vacuum-Assisted vs Conventional Minimally Invasive Percutaneous Nephrolithotomy for the Treatment of Two-to-Four-Centimeter Stones: A Multicenter Prospective and Randomized Trial

Introduction: Percutaneous nephrolithotomy (PCNL) is the recommended treatment for 2-4-cm renal stones. Minimally invasive PCNL (MPCNL) with ≤22F sheath was frequently used instead of standard PCNL. MPCNL uses pressurized irrigation to flush out stone fragments through a conventional nephrostomy sheath (cNS), which may result in higher intrarenal pressure (IRP) and longer operating time. The novel vacuum-assisted nephrostomy sheath (vaNS) was developed to mitigate higher IRP and to facilitate stone removal. It might improve the performance of MPCNL. This prospective and randomized trial compares these two sheaths. Materials and Methods: In total, 120 patients with 2-4-cm renal stones were accrued in six tertiary medical centers with equal numbers in 2021. In total, 120 patients underwent mPCNL, 60 using 18F cNS and 60 using 18F vaNS, in a prospective and randomized assignment. The primary outcome measurement is decrease in IRP. The secondary outcome is efficacy in stone retrieval. Results: The IRP was lower with vaNS than with cNS: mean IRP during lithotripsy was 12.0 ± 2.7 mm Hg with vaNS vs 20.4 ± 6.0 mm Hg with cNS, p = 0.000. IRP duration ≥30 mm Hg was shorter with vaNS than with cNS (6.7 ± 7.4 seconds vs 113.4 ± 222.7 seconds, p = 0.001). vaNS has shorter stone removal time (26.9 ± 14.3 minutes vs 35.7 ± 11.8 minutes, p = 0.000). Stone extraction rate was higher (166.4 ± 88.1 mm3/min vs 90.4 ± 31.7 mm3/min, p = 0.000). Stone grasper usage was less (1.4 ± 2.6 vs 11.9 ± 9.7, p = 0.000). vaNS maintained the safety profile. Blood loss, creatinine changes, perioperative complications, and hospital stays were the same in both groups, all p > 0.05. Conclusion: MPCNL for stones 2-4 cm using vaNS has shorter stone removal time, higher stone extraction rate, and less use of stone extractor. vaNS is superior to cNS at reducing IRP and is associated with improved stone free rates at 3 days but not at 30 days postoperatively. The trial was registered with Chinese Clinical Trial Registry (ClinicalTrials.gov, NCT ChiCTR2000039681).