Evaluation of a Polymeric Flap Valve-Attached Ureteral Stent for Preventing Vesicoureteral Reflux in Elevated Intravesical Pressure Conditions: A Pilot Study Using a Porcine Model

Abstract

Objective: To evaluate the effectiveness of a polymeric flap valve-attached ureteral stent for preventing vesicoureteral reflux (VUR) in an animal model. Materials and Methods: One female Yorkshire pig was included in this study. A flap valve-attached and a conventional stent was inserted in the right and left ureters, respectively. The bladder was filled with contrast medium until the intravesical pressure reached 20cm H2O. Subsequently, simulated voiding cystourethrography (VCUG) was performed 50 times by manually compressing the suprapubic area until the intravesical pressure reached 50cm H2O. Intravenous pyelography (IVP) was performed thereafter to evaluate the urinary drainage. In addition, an in vitro durability test of the function of the flap valve was conducted under continuous hydrostatic pressure for 24h. Results: The volume of contrast medium needed to achieve an intravesical pressure of 20cm H2O was 1740mL. In the repeated simulated VCUG for the right ureter, VUR grades of 0 and I were recorded in 82.0 (n=41) and 18.0% (n=9) tests, respectively, whereas for the left ureter, grades of I, II, and III were recorded in 14.0 (n=7), 82.0 (n=41), and 4.0% (n=2), respectively. Thus, a significantly lower VUR grade was recorded for the right ureter than for the left ureter (p˂0.001). In the bilateral VUR condition, the pressure for VUR occurrence was significantly greater in the right ureter than in the left ureter (p=0.007). No urinary obstruction was caused by the flap valve-attached ureteral stent according to the IVP findings. The in vitro durability test demonstrated slightly enhanced antireflux function and slightly decreased intraluminal drainage at 12h, and these findings sustained thereafter. Conclusion: A flap valve-attached ureteral stent effectively prevented VUR under conditions of elevated intravesical pressure without urinary obstruction.