Does the drainage of irrigation through the ureteral access sheath have an impact on the results of primary retrograde intrarenal surgery?

Purpose: One of the risk factors associated with post-operative fever and infections is the amount of fluid absorbed by the kidney. We conducted a prospective study to analyse the effects of irrigation fluid inflow and outflow on post-operative complications and stone-free rate. Material and methods: We did a prospective study on all primary retrograde intrarenal surgery (RIRS) cases performed at our hospital between JAN 2020 and JAN 2023. The fluid draining out of the access sheath was collected in a measuring container until the flexible scope was inside the access sheath. The amount of fluid retained by the body was measured by calculating the difference between the quantity of irrigation fluid utilised and the output from the access sheath. Results: A total of 566 patients were included in the study. The retained volume of more than 100 ml was associated with more pain (0.0/426 vs 49/140, p < 0.001), a higher incidence of fever (7/426 vs 22/140, p < 0.001), a higher incidence of high-grade complications (G4A 0 vs 4), and a higher incidence of residual stones (11/426 vs 49/140, p < 0.001). Conclusion: The outflow from the access sheath is a crucial factor that can significantly impact the outcome of RIRS.