Computational Fluid Dynamics Assessment of Various Ureteroscope Cross Sections to Reduce Intra- pelvic Pressure

Abstract Background High intrapelvic pressure (IPP) during ureteroscopy can lead to complications such as pyelovenous backflow, bleeding, and infection. Our study aimed at identifying the best cross-section and orientation of a ureteroscope within a Ureteral Access Sheath (UAS) to minimize IPP and maximize outflow. We have also validated our findings by testing a UAS prototype.Materials and Methods To determine the optimal ureteroscope cross-section within a UAS, four ureteroscopes of equivalent cross-sectional area were simulated within a 10 Fr UAS using computational fluid dynamics software COMSOL. We then created a corresponding prototype by securing a 3 − 0 monofilament suture at the inferior aspect of the 12 Fr outer UAS, inducing an offset to the ureteroscope. Mean flow volumes through a 10/12 Fr UAS occupied by a 9.5 Fr single-use flexible ureteroscope were compared (17 iterations) to those through our prototype UAS.Results Compared to a ureteroscope centered in a UAS during simulation, the lowest IPP and highest outflow were seen with an offset circular ureteroscope (41% resistance). The unmodified UAS had an average volume of 30.0 mL/minute (SD +/- 0.35) compared to 33.76 mL/minute (SD +/-0.90) for the modified UAS (P < 0.05).Conclusions We found that using a circular ureteroscope positioned along the sidewall maximizes outflow through a circular UAS. We made modifications to a UAS to offset the ureteroscope and observed a 12.5% increase in outflow. This approach can potentially decrease IPP during ureteroscopy without impacting inflow or the working channel. Although modifying a ureteroscope is more difficult, it could create an offset without reducing UAS cross-section.