Standardization of retrograde intrarenal surgery with "gravity irrigation" technique leads to low postoperative infection rate regardless of surgeon experience.

Objectives: We aimed to evaluate the prevalence and predictive factors of postoperative infections after a standardized low-pressure RIRS technique. The secondary outcome was comparing surgeons' experience in terms of infective complication and stone-free rate.

Methods: A single-center retrospective analysis was conducted on all patients who underwent RIRS for kidney stones between January 2018 and February 2019.

Inclusion Criteria: adults, stone ≤ 20 mm (unless percutaneous nephrolithotomy contraindica-tions). Concomitant ureteral lithotripsy was allowed.

Exclusion Criteria: bilateral surgery, active urinary tract infections (UTI), pregnancy, fever at surgery. Low-pressure RIRS and ureteroscopy was achieved with gravity irrigation, a 5 Ch open-ended urethral catheter (ureteral lithotripsy), intravenous furosemide (20 mg), and ureteral access sheath above the ureteral-pelvic junction (RIRS).

Results: 236 patients were included in the analysis. Mean age was 55.89±13.96 years. Mean stone diameter was 14.28±5.81mm. 43 (18.2%) patients underwent concomitant ureteral lithotripsy. Mean operative time was 61.10 ± 31.36 minutes. Infective complications occurred in 13 (5.5%) patients. Sepsis occurred in 10 (4.2%) patients and septic shock occurred in 1 (0.4%). One patient (0.4%) required stent substitution. Multivariate logistic regression analysis showed that history of UTI predicted for higher risk of postoperative infections (OR 8.434, CI 95% 2.36-29.46). Outcomes comparison of surgical expertise did not statistically differ in terms of stone-free rate and infective complications.

Conclusion: Our standardized RIRS technique achieved a low postoperative infective complication rate. History of UTI was the strongest predictor of postoperative infections.