Abstract:Abstract: Objectives To investigate the relationship between the status of ureteral access sheath (UAS) and the flow rate of perfusion fluid in the sheath, discovering the pressure in the renal pelvis at 150mmHg Wolf pump perfusion. Methods 18 patients with flexible ureteroscope operations were divided into three groups: A, B and C, according to the three states of UAS (F12/14), 6 cases in each group. We detected the intrathecal flow velocity after URF-P5 flexible ureteroscope were placing into the renal pelvis and when placing 200 um fiber crushed stone. In group C which the UAS condition assessment is not satisfying, intrathecal guidewire was applied to improve the intrathecal velocity. We measured the internal pressure of the renal pelvis 1 case with renal fistula. Results The intrathecal velocity of URF-P5 in group A, B and C was (54.22 ± 2.14) ml/min, (47.32 ± 2.39) ml/min, and (25.01 ± 2.54) ml/min, respectively, after perfusion with 150 mmHg Wolf pump. The intrathecal flow rate was (32.68 ± 2.23) ml/min, (30.44 ± 2.58) ml/min, and (24.15 ± 2.22) ml/min, respectively. The flow rate of intrathecal guidewire placement in group C was (28.64 ± 2.18) ml/min, which increased by 13.0% ~ 21.0% and the average flow rate increased by 18.6% compared with that before guide wire placement. The renal pelvic pressure was 11 mmHg at rest. After entering the renal pelvis, the renal pelvic pressure was 28 ~ 51 mmHg with a median value of 38 mmHg. The renal pelvic pressure was 55 ~ 72 mmHg and the median value was 68 mmHg at holmium laser lithotripsy. The renal pelvic pressure decreased to 38 ~ 61 mmHg and the median value was 50 mmHg after intrathecal guidewire. Conclusions Different states of UAS lead to different outflow rates of perfusion fluid, and outflow rates could reflect the pressure of renal pelvis indirectly. It is relatively safe to use F12/14 UAS, URF-P5 flexible ureteroscope, Wolf pump perfusion pressure limit of 150 mmHg. The operation time should be controlled when the condition assessment of UAS is not satisfying and intrathecal guidewire is needed to reduce renal pelvic pressure through increasing intrathecal flow rate.