ABSTRACT
Background and Purpose: This study aimed to evaluate the characteristics of ureteral access sheaths (UASs) that can reduce the insertion force while accessing the upper urinary tract. Materials and Methods: Six different types of 12/14F UASs were used. We evaluated the properties of UASs such as the diameter of the outer sheath, length of the inner dilator tip exposed from the outer sheath, sheath flexibility (assessed in terms of bending force of the tip or base), flexibility ratio (i.e., bending force value of tip-to-base ratio), and frictional force of the outer sheath surface. We measured the force required for inserting the UAS into an artificial ureteral model and examined the correlation between the relevant characteristics and insertion force for each UAS. Results: Overall, a lower tip-to-base flexibility ratio (r = 0.66) and a lower frictional force (r = 0.50) were inversely correlated with insertion force. The force of insertion into the bifurcation was associated with the flexibility of the base (r = -0.64), flexibility ratio (r = 0.79), and frictional force (r = 0.66). Moreover, a shorter dilator tip (r = 0.52), lower flexibility ratio (r = 0.52), and lower frictional force (r = 0.50) were correlated with a lower insertion force at the proximal ureter. Conclusion: A UAS with a rigid base and flexible tip parts, a smoother surface, and a shorter dilator tip would be preferable for reducing the insertion force. These findings may be crucial for selecting or developing an ideal UAS that can decrease the risk of ureteral injury.
Subject(s)
Ureter , Urologic Diseases , Humans , Ureter/surgery , UreteroscopyABSTRACT
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.
