A Feasibility Study on the Efficacy and Safety of a Novel Tip-Flexible Suction Ureteral Access Sheath Combined with Flexible Ureteroscopic Lithotripsy for Treating Kidney Stones ≥30 mm

<b><i>Objective:</i></b> To evaluate the efficacy and safety of a novel tip-flexible suction ureteral access sheath (NTFS-UAS) combined with flexible ureteroscopic lithotripsy (FURS) for treating kidney stones ≥30 mm in a large cohort. <b><i>Methods:</i></b> The clinical data of 206 patients with renal calculi ≥30 mm treated by NTFS-UAS combined with FURS from June 2021 to September 2023 were analyzed retrospectively. The outcomes under investigation encompassed demographic information, stone-related characteristics, operative time, stone-free rates (SFRs), and postoperative complications. <b><i>Results:</i></b> The median operation duration was 110 minutes (interquartile 84.00-146.25 minutes). Immediate and 1-month SFRs were 83.98% and 85.44%, respectively. Multivariate analysis revealed five risk factors independently affecting stone clearance rate: stone size (≥50 mm, odds ratio [OR] = 3.826, <i>p</i> = 0.039), stone number (multiple: OR = 8.745, <i>p</i> = 0.015), stone location (multiple calyces: OR = 10.371, <i>p</i> = 0.045; lower calyx: OR = 9.615, <i>p</i> = 0.047), severe hydronephrosis (OR = 8.338, <i>p</i> = 0.002), and the Resorlu-Unsal scoring system (RUSS) score (6-7: OR = 10.829, <i>p</i> = 0.009; 4-5: OR = 4.223, <i>p</i> = 0.008). The incidence of Clavien-Dindo grade II-III complication was 5.82%. Positive preoperative urine culture (OR = 9.533, <i>p</i> = 0.012) and RUSS score (6-7: OR = 25.678, <i>p</i> = 0.026; 4-5: OR = 11.444, <i>p</i> = 0.038) were identified as the most important variables that may contribute to the development of high-grade postoperative complications. <b><i>Conclusion:</i></b> NFTS-UAS combined with FURS achieved satisfactory outcomes with good efficacy and safety for treating large renal stones ≥30 mm, and it can be utilized as an effective treatment option for patients having contraindications or preference against percutaneous nephrolithotomy. In addition, clinical factors, such as stone size, severe hydronephrosis, positive preoperative urine culture, and RUSS stone score that likely affected the outcomes of NFTS-UAS, should be fully taken into account when the surgeon performing FURS using NFTS-UAS.