The Effect of Ratio of Endoscope-Sheath Diameter on Intrapelvic Pressure During Flexible Ureteroscopic Lasertripsy

Purpose: To clarify appropriate combinations of flexible ureteroscope (FURS) and ureteral access sheath (UAS), which can maintain a low intrapelvic pressure (IPP) during FURS with lasertripsy. Methods: Four kinds of FURSs (Polyscope, Olympus URF-P6, Stroz Flex-Xc, and Olympus URF-V) and six sizes of UASs (11/13F × 36 cm, 11/13F × 46 cm, 12/14F × 36 cm, 12/14F × 46 cm, 13/15F × 36 cm, and 13/15F × 46 cm) were tested. A novel gas-liquid-pressure-control system (GLPCS) was used to maintain a stable and adjustable irrigation pressure form 50–500 cmH2O. IPPs and flow rates were recorded with different combinations of FURSs and UASs by using an in vitro fresh cadaveric porcine urinary system. Results: The GLPCS can provide stable and adjustable water pressure. The ratio of outer diameter of FURSs and inner diameter of UASs (Ratio of Endoscope-Sheath Diameter—RESD) is essential to the IPP and flow rate. The highest IPP group is the combination of Olympus URS-V and 11/13F UAS with RESD of 0.87–0.88, the IPP is over 40 cmH2O when irrigation pressure comes to 250 cmH2O; Olympus URS-V in 12/14F UAS is at the middle group, RESD values of 0.81–0.82, IPP reaches 40 cmH2O at 500 cmH2O of irrigation pressure. Combinations with RESD ≤0.75 enjoy low IPPs (<13 cmH2O). Polyscope with 13/15F UASs has the highest flow rate (74.3–77.7 mL/min), whereas Olympus URS-V with 11/13F UASs has the lowest flow rate (17.0–17.3 mL/min). UAS length has less effect on the IPP and flow rate. Conclusions: To maintain a low IPP and acceptable flow rate during flexible ureteroscope lasertripsy, RESD should be kept below 0.75. UAS length has less effect on the IPP and flow rate.