Optimizing aspiration efficiency in RIRS: the impact of ratio of endoscope-sheath diameter, irrigation flow, and negative pressure in an vitro study.

Abstract

To examine the impact of ratio of endoscope-sheath diameter (RESD), irrigation rate, and negative pressure on the efficiency of stone fragment aspiration during retrograde intrarenal surgery (RIRS) in an in vitro setting. Five grams of stone fragment were precisely measured and placed in renal calyx. A flexible ureteroscope with a Flexible Adjustable Navigation Suction Ureteral Access Sheath (FANS) was introduced into the renal calyx, connected to an irrigation pump and suction pump. A urologist performed 1-minute simulated intraoperative aspiration maneuvers. Residual stone dust was collected from the suction system, dried, and reweighed. Experimental variables included ureteroscope dimensions (7.5Fr and 8.6Fr), FANS sizes (10/12Fr and 12/14Fr), negative pressure levels (0.02 MPa and 0.01 MPa), and irrigation flow rates (100, 150, 200, 250, and 300 ml/min). Intrarenal pelvic pressure was monitored in real time with a digital pressure transducer probe in the renal pelvis. Experiments were conducted in the upper, middle, and lower calyces, with each parameter combination repeated five times in a randomized order to ensure statistical reliability.The study demonstrated that under low negative pressure (0.01 MPa), stone fragment aspiration efficiency exhibited a parabolic relationship with irrigation flow rate. Maximum efficiency was observed at 200 ml/min across all ureteroscope-FANS configurations. Elevating negative pressure to 0.02 MPa significantly enhanced aspiration efficiency, with peak performance maintained at 200 ml/min. The different positions of the renal calyces have a significant impact on the aspiration efficiency, and the aspiration efficiency of the lower calyx is significantly lower than that of the upper and middle calyces. Smaller FANS-to-endoscope ratios (e.g., 10/12Fr UAS with 7.5Fr f-URS, RESD = 0.75) demonstrated 27.2% lower aspiration efficiency compared to larger sheaths (12/14Fr FANS, RESD = 0.64) at 200 ml/min under 0.02 MPa (P < 0.001). All f-URS and FANS configurations maintained intrapelvic pressure (IPP) within safe thresholds across varying irrigation flow rates and negative pressure conditions.The efficiency and safety of stone fragment aspiration is high when the infusion rate is 200 ml/min and the negative pressure is 0.02Mpa. A smaller RESD leads to greater aspiration efficiency.