Stone displacement with combined Sotn ureteroscopy and flexible ureteroscopy for lower calyx stones ⩽20 mm: a retrospective comparative study

Background: The lower calyx is the most common site for kidney stones. While minimally invasive, flexible ureteroscopic lithotripsy often yields suboptimal stone-free rates (SFR) for lower calyx stones due to anatomical constraints and limited endoscope deflection. Objectives: To evaluate the efficacy and safety of a novel technique that combines Sotn ureteroscopy (Sotn-URS) with flexible ureteroscopy (fURS), involving stone displacement before lithotripsy, for managing lower calyx stones ⩽20 mm. Design: A retrospective comparative study complemented by in vitro simulation experiments. Methods: = 126). The experimental group underwent combined Sotn-URS and fURS with basket-assisted stone displacement to the kidney pelvis or upper ureter before laser lithotripsy. The control group underwent conventional in situ lithotripsy using fURS alone. Outcomes, including operative time, SFR (immediate and at 4 weeks), surgeon comfort (Borg scale), first-pass sheath placement success, and complications, were compared. Results: < 0.05). Conclusion: The stone displacement technique utilizing combined Sotn-URS and fURS is an efficient and safe surgical approach for lower calyx stones ⩽20 mm. It uses the stable access and efficient lithotripsy of rigid Sotn-URS and the flexibility of fURS for stone displacement, resulting in improved stone clearance rates, reduced operative time, and lower ureteral injury risk.