Evaluation of Intrapelvic Pressure When Using Small-Sized Ureteral Access Sheaths of ≤10/12F in an Ex Vivo Porcine Kidney Model

Background and purpose: Although several different ureteral access sheaths (UASs) of ≤10/12F are commercially available, their advantages and disadvantages during retrograde intrarenal surgery (RIRS) are still unknown. This study aimed to evaluate the difference in intrapelvic pressure (IPP) between different UASs of ≤10/12F with several irrigation pressure settings.

Materials and methods: Five different commercially available UASs (9.5/11.5F Flexor^®, 10/12F ReTrace^®, 10/12F Bi-Flex^®, 10/12F Proxis^®, and 10/12F UroPass^®) with the thinnest ureteroscope (UFR-P6^®) were tested with eight different irrigation pressures (40-180 mbar) in an ex vivo porcine kidney model. Diameters of each part of the UASs were measured using a digimatic caliper, and IPP and irrigation outflow (IOF) rates were evaluated at the time of reaching the plateau of maximum IPP.

Results: The 9.5/11.5F Flexor had the narrowest inner diameter and the 10/12F UroPass had the widest outer diameter among UASs (both p < 0.05). The 10/12F UroPass and 10/12F Bi-Flex provided an IPP below 40 cm H₂O at all irrigation pressures, whereas the 9.5/11.5F Flexor, 10/12F Proxis, and 10/12F ReTrace provided such an IPP at irrigation pressures of <60, 120, and 120 mbar, respectively. Similar to IPP, the 10/12F UroPass and 10/12F Bi-Flex had a significantly higher IOF rate than that of the other UASs at all irrigation pressures (both p < 0.05).

Conclusion: The 9.5/11.5F Flexor is the thinnest UAS and may provide excessive IPP during RIRS. Among 10/12F UASs, 10/12F UroPass and 10/12F Bi-Flex can provide a safe IPP and good IOF at any irrigation pressure.