Objective:Objectives To introduce the preliminary experience of flexible vacuum-assisted ureteral access sheath(FV-UAS) in the treatment of upper urinary calculi in retrograde intrarenal lithotripsy(RIRS).Methods:The clinical data of 11 patients with upper urinary calculi who were treated in Jiangxi Provincial People's Hospital from August to September 2021 were analyzed retrospectively. There were 6 males and 5 females, with the mean age of 48 years (32-72 years), the mean size of stone of 15.5 mm (11-20mm), and the mean stone volume of 1 958 mm3 (1 108-4 036 mm3), including 1 case with upper ureteral calculi, 10 cases with renal calculi, and 2 cases with calculi in multiple renal calyces. Ureteral stents were placed in 2 cases preoperatively. There were 2 cases of grade Ⅱ hydronephrosis according to Grignon classification. All patients were treated by retrograde intrarenal lithotripsy, and the FV-UAS(F12/14) was used during the operation. FV-UAS can be passively bent(>90°) with the bending of the flexible ureteroscopy(f-URS), and connect vacuum suction devices. The method of placing the FV-UAS during the operation was the same as traditional ureteral access sheath. The FV-UAS should be as close to the target stone as possible by the f-URS during the operation. F6 ureteral stent was routinely indwelled for 2-4 weeks. The operation time, postoperative complications, and stone volume clearance rate were summarized and analyzed, and stone volume clearance rate was calculated as(1-residual stone volume/preoperative stone volume)×100%. The stone volume was obtained by CT 3-D reconstruction preoperatively and first day postoperatively.Results:All patients underwent RIRS successfully at the first stage, with the usage of FV-UAS(F12/14)during the operation. The mean operation time was 57.1 minutes(34-90 minutes), and the mean stone volume clearance rate was 98.9%(94.8%-100.0%)on the first day postoperatively. Seven cases reached 100.0% stone-free rate, and 4 cases presented residual calculi. The mean hemoglobin drop was 0.8 g/L, and 1 case presented vomiting without fever on the first day postoperatively. For the 4 cases with residual calculi, no residual stone was found by B-ultrasound when the ureteral stent was removed.Conclusions:Our preliminary study found that it is feasible and safe to use FV-UAS in RIRS, which can follow the f-URS to extend into the renal pelvis and renal calyces. Vacuum-assist can increase the probability of stone-free.