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 cmH2 O. 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 cmH2 O when irrigation pressure comes to 250 cmH2 O; Olympus URS-V in 12/14F UAS is at the middle group, RESD values of 0.81-0.82, IPP reaches 40 cmH2 O at 500 cmH2 O of irrigation pressure. Combinations with RESD ≤0.75 enjoy low IPPs (<13 cmH2 O). 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.