title: A novel dual-diameter ureteroscope working channel: impact on irrigant flow.
abstract: OBJECTIVE
  To compare irrigant flow characteristics through standard working channels (3.6F to 4.5F) and a dual-diameter working channel. Irrigant flow is critical for adequate visualization during endoscopic procedures.
  
  
  METHODS
  Working channels were created out of 80 cm of light wall polytetrafluoroethylene (PTFE) tubing (inner diameter 3.6F, 4.0F, and 4.5F) with a male Luer connector attached to one end by epoxy resin. The dual-diameter working channel was created with a 70-cm segment of PTFE (4.5F inner diameter, 0.059 in.) and a 10-cm segment of PTFE (3.6F inner diameter, 0.047 in.) with a male Luer connector attached to the free end of the 4.5F tubing. Stone basket shafts (100 cm in length, outer diameter 1.9F, 2.4F, and 3.0F) were created out of unmodified polyimide tubing with a 0.018-in.-diameter nitinol mandrel epoxy core for stability. Irrigant flow was measured at 100 mm Hg pressure for 1 minute with an empty channel and with stone basket shafts in the channel.
  
  
  RESULTS
  The flow rates were significantly greater with the dual-diameter working channel than with the standard flexible ureteroscope (3.6F) working channel using an empty channel (79.2 versus 44.1 mL/min, P = 0.0001), 1.9F basket (35.9 versus 10.0 mL/min, P = 0.003), 2.4F basket (20.7 versus 4.3 mL/min, P = 0.002), and 3.0F basket (6.0 versus 0.7 mL/min, P = 0.0002) sheath.
  
  
  CONCLUSIONS
  A dual-diameter working channel may optimize irrigant flow characteristics for flexible ureteroscopes while maintaining a small distal tip diameter.
authors.affiliation: Department of Urologic Surgery, University of Minnesota Medical School and the VAHCS Minneapolis, Minneapolis, Minnesota 55455, USA.
authors.forename: Manoj
authors.initials: M
authors.lastname: Monga
authors.forename: Kari
authors.initials: K
authors.lastname: Hendlin
authors.forename: Jason
authors.initials: J
authors.lastname: Skenazy
authors.forename: Anup
authors.initials: A
authors.lastname: Ramani
mesh_terms: D011138:Polytetrafluoroethylene; D012212:Rheology; D007507:Therapeutic Irrigation / Q000295:instrumentation / Q000379:methods; D020709:Ureteroscopes; D018666:Ureteroscopy / Q000379:methods
chemical_list: D011138:Polytetrafluoroethylene