title: Anti-Reflux Ureteral Stent with Polymeric Flap Valve Using Three-Dimensional Printing: An In Vitro Study.
abstract: OBJECTIVE
  This article aims to describe the design of an anti-reflux ureteral stent with a polymeric flap valve and the fabrication methods using three-dimensional (3D) printing. The stent effectively prevents backward flow with a negligible reduction in forward flow. Fabrication of miniaturized valves was easy with high precision and rapid prototyping.
  
  
  METHODS
  The proposed stent comprised a 7F Double-J (DJ) stent and a polymeric flap valve. The valve was made of Tango Plus FLX980 and was fabricated using a 3D printer. Two types of stent were prepared for in vitro tests: DJ stents with (1) an uncoated valve (UCV) stent and (2) a parylene C coated valve (PCV) stent for enhanced biocompatibility. The flow characteristics of each stent were evaluated considering flow direction, parylene coating, and stent side holes, and were compared to the intact DJ stent.
  
  
  RESULTS
  The forward flow rate for the distal portion of the UCV and PCV stents was 9.8 mL/min and 7.8 mL/min at applied pressure of 15 cm H2O (normal anterograde pressure in patients with stents), respectively. Backward flow rate for the distal portion of the UCV and PCV stents was decreased by 28 times and 8 times at applied pressure of 50 cm H2O (maximum bladder pressure), respectively, compared with the distal portion of the intact DJ stent. Forward flow rates of whole stents were 22.2 mL/min (UCV stent) and 20.0 mL/min (PCV stent) at applied pressure of 15 cm H2O, and backward flow rates of whole UCV and PCV stents were decreased by 8.3 times and 4.0 times at applied pressure of 50 cm H2O, respectively, compared with the intact DJ stent.
  
  
  CONCLUSIONS
  The anti-reflux ureteral stent was successfully designed and fabricated using a 3D printer. In vitro studies showed that the stent effectively prevented backward flow while minimizing reduction in forward flow.
authors: 1 Department of Medical System Engineering, Gwangju Institute of Science and Technology (GIST) , Gwangju, South Korea .
authors: Chang-Ju
authors: CJ
authors: Park
authors: 1 Department of Medical System Engineering, Gwangju Institute of Science and Technology (GIST) , Gwangju, South Korea .
authors: Hyeon-Woo
authors: HW
authors: Kim
authors: 1 Department of Medical System Engineering, Gwangju Institute of Science and Technology (GIST) , Gwangju, South Korea .
authors: Sangdo
authors: S
authors: Jeong
authors: 2 School of Mechotronics, Gwangju Institute of Science and Technology (GIST) , Gwangju, South Korea .
authors: Seungwan
authors: S
authors: Seo
authors: 1 Department of Medical System Engineering, Gwangju Institute of Science and Technology (GIST) , Gwangju, South Korea .
authors: Yangkyu
authors: Y
authors: Park
authors: 3 Department of Urology, College of Medicine, Hanyang University , Guri, South Korea .
authors: Hong Sang
authors: HS
authors: Moon
authors: 1 Department of Medical System Engineering, Gwangju Institute of Science and Technology (GIST) , Gwangju, South Korea .
authors: Jong-Hyun
authors: JH
authors: Lee
mesh_terms: D001672:Biocompatible Materials; D004867:Equipment Design / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D011108:Polymers; D066330:Printing, Three-Dimensional; D015607:Stents; D014718:Vesico-Ureteral Reflux / Q000601:surgery*; D014992:Xylenes
chemical_list: D001672:Biocompatible Materials; D011108:Polymers; D014992:Xylenes; C011055:parylene