Efficacy and Safety of Mini-PCNL Versus Standard-PCNL For The Management of 20-40 mm Size Kidney Stones: A Multi-center Randomized Controlled Trial

To evaluate the efficacy and safety of mini-PCNL versus standard-PCNL for the management of 20-40 mm size kidney stones.Investigators plan to do a multicenter, parallel, open-label randomized controlled trial (RCT). There are 20 hospitals included in this study, including The First Affiliated Hospital of Guangzhou Medical University, Baoshan No.2 People's Hospital, The second Affiliated Hospital of Harbin Medical University, The First Affiliated Hospital of Fujian Medical University, People's Hospital of Nanhai District, Yichang Yiling Hospital, Suzhou Municipal Hospital, Jining NO.1 People's Hospital, The First Affiliated Hospital of Gannan Medical University, The General Hospital of Shenyang Military, Shanghai General Hospital, Qingyuan People's Hospital, The second Affiliated Hospital of Kunming Medical University, Beijing Chuiyangliu Hospital, Fujian Medical University Union Hospital, ShengJing Hospital of China Medical University, 181st hospital of Chinese People's Liberation Army, The First Affiliated Hospital of Guangxi Medical University, China-Japan Union Hospital, Jilin University, Jiangmen Hospital of Zhongshan University.

Each center performs more than 500 PNL procedures per year. Ethics committee approval was obtained at each site and informed consent was taken from each patient. The primary endpoint was the one-session SFR and the secondary endpoints included intraoperative and postoperative parameters.

This study will be started at January,2016 and ended at November ,2019. The SFR of sPNL and mPNL was assumed to be 83% and 89% respectively, based on the earlier data. -10% was considered as a non-inferiority margin. the type-1 error (α) was set to 0.05 and the power (1-β) to 0.8. Sampling ratio was 1. According to the formulas of 2-sample non-inferiority test comparing two proportions, the minimum sample size for each group was 923 using a power and sample size calculator (HyLown Consulting, Atlanta). Considering the patients lost to follow-up and consent withdrawals, the number was increased to 1000 patients in each group.

Randomization We used SPSS software to generate 2000 random numbers in a table with a ratio of 1:1 ("0" for sPNL and "1" for mPNL). A protocol-blinded coordinator revealed the assignment in sequence to the center once the consent was signed and surgery was scheduled. The number of included patients was not equally distributed among the centers.

Quality control A standard operating procedure (SOP) was made and approved by the principal investigator of each center. Routine monitoring visits to all centers were carried out every month.