Flexible ureteroscopy with a flexible and navigable suction ureteral access sheath versus mini-percutaneous nephrolithotomy for 1–2 cm lower pole renal stones: Protocol for an international, multicentre, randomized non-inferiority trial (FLAME trial)

Wei Zhu Jinghua Zhong Kefeng Wang Guangming Yin Chi-Ho Leung Nariman Gadzhiev Mehmet Ilker Gökce Jaisukh Kalathia Vineet Gauhar Guangyuan Zhang Gang Wu Mingyong Li Li Fang Shaohua Zeng Peide Bai Ji Li Zhenhua Zhao Ming Xi Xin Mai Xianzhong Duan Kehua Jiang Jianwei Cao Xianghu Meng Shusheng Liu Aram Aloyan Peng Yuan Xiaorui Zhu Ting Huang Jianhui Xing Jingzeng Du Wenqi Wu Jinxiang Ma Wen Zhong Zhijian Zhao Yongda Liu Chi Fai Ng Jean de la Rosette Bhaskar Somani Shiyong Qi Guohua Zeng Steffi Kar Kei Yuen Flexible ureteroscopy with a flexible and navigable suction ureteral access sheath versus mini-percutaneous nephrolithotomy for 1–2 cm lower pole renal stones: Protocol for an international, multicentre, randomized non-inferiority trial (FLAME trial) FANS flexible and navigable suction ureteral access sheath flexible ureteroscopy lower pole PCNL renal stones Scopus Web of Science 2025

2026-05-24

10.1002/bco2.70114 BJUI COMPASS Background: Lower pole renal stones measuring 1–2 cm remain challenging to treat. While mini-percutaneous nephrolithotomy (mini-PCNL) provides high stone-free rates (SFRs), it carries tract-related morbidity. Flexible ureteroscopy (f-URS) is less invasive but limited in SFR. The flexible and navigable suction ureteral access sheath (FANS) has shown promise in improving stone evacuation and intrarenal pressure control. We hypothesize that FANS f-URS is non-inferior to mini-PCNL for patients with 1–2 cm lower pole stones in SFR. Study Design: The FLAME trial is an international, multicentre, randomized, noninferiority study directly comparing FANS-f-URS with mini-PCNL in this setting. Endpoints: The primary outcome is immediate SFR within 72 hours on low-dose CT. Secondary outcomes include SFR at 1 month, operative time, postoperative pain, hospital stay, complications (Clavien–Dindo) and quality-of-life changes. Patients and Methods: A total of 640 adults with CT-confirmed 1–2 cm lower pole renal stones will be randomized 1:1 to undergo FANS-f-URS or mini-PCNL across 20 high-volume urology centres worldwide. Randomization is centralized and stratified by site. Radiologists and statisticians will remain blinded to allocation. Sample size was calculated assuming an 85% SFR for both arms, an 8.5% non-inferiority margin, 80% power and 15% attrition. Analyses will follow both intention-to-treat and per-protocol principles.

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