Objective: To evaluate the long-term stone-free rate (SFR) of retrograde intra-renal surgery (RIRS) in the treatment of lower pole renal calculi using only basket relocation and identify independent predictors of stone-free status.

Methods: All consecutive patients undergoing RIRS lower pole renal calculi at a single high-volume tertiary center were analyzed retrospectively. Lower pole stones were relocated to the upper pole, where laser lithotripsy was performed. All patients were followed up in the clinic following the surgery and yearly thereafter. The stone-free status was assessed with a combination of an abdominal ultrasound and abdominal X-ray, or an abdominal non-contrast computed tomography if the stones were known to be radiolucent.

Results: A total of 480 consecutive patients who underwent RIRS for treatment of lower pole renal calculi, between January 2012 and December 2018, were analyzed from a prospectively maintained database of 3000 ureteroscopies. With a median follow-up time of 18.6 months, the mean SFR was 94.8%. The procedures were unsuccessful in 26 (5.4%) patients due to unreachable stones. The median stone size of the unreachable stones was 12 mm (range 10-30 mm). Multivariable logistic regression analysis revealed two predictors of SFR for lower pole stones: a small cumulative stone burden (odds ratio [OR]: 0.903, 95% confidence interval [CI]: 0.867-0.941, p<0.0001) and preoperative ureteral stent insertion (OR: 0.515, 95% CI: 0.318-0.835, p=0.007).

Conclusion: The long-term SFR of RIRS for the treatment of lower pole stones with basket displacement with appropriate patient selection is high.