title: A safety guidewire influences the pushing and pulling forces needed to move the ureteroscope in the ureter: a clinical randomized, crossover study.
abstract: OBJECTIVE
  It is generally advised to keep a safety guidewire (SGW) in the ureter alongside the ureteroscope during endoscopy of the upper urinary tract, but little is known of how the SGW influences the forces exerted on the ureteroscope in the ureter. The purpose of this study was to investigate whether the presence of an SGW during ureteroscopy (URS) in a normal clinical setting will influence the pushing and pulling forces exerted on a semirigid ureteroscope.
  
  
  METHODS
  In a 1-year period (2010-2011), 40 patients admitted to Haukeland University Hospital for endoscopic treatment of renal pelvic stone disease were included in a clinical randomized crossover trial measuring the forces needed to move a semirigid ureteroscope during URS. A digital force meter was connected to the ureteroscope to perform the force measurements. The pushing and pulling forces were measured at four locations during URS with and without an SGW. The patients were randomized to whether the first series of force measurements should be with or without SGW. Paired-samples t tests were used comparing the forces in the two series.
  
  
  RESULTS
  Significantly higher forces were found both when inserting and retracting the semirigid endoscope when an SGW was used compared with times when an SGW was omitted. The mean percentage increase in the forces with an SGW in place varied between 51.8% and 112.5% across locations and directions. A limitation is that the study has been performed with a semirigid ureteroscope only.
  
  
  CONCLUSIONS
  An SGW substantially increased the resistance against moving a semirigid ureteroscope up and down the ureter. The SGW may thus be an obstacle to the ureteroscopic procedure and may even increase the risk of harming the ureter in some patients.
authors.affiliation: Department of Urology, Haukeland University Hospital, Bergen, Norway. doc.ulvik@online.no
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Ulvik
authors.forename: Tore
authors.initials: T
authors.lastname: Wentzel-Larsen
authors.forename: Nils M
authors.initials: NM
authors.lastname: Ulvik
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018592:Cross-Over Studies; D004867:Equipment Design; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007669:Kidney Calculi / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013314:Stress, Mechanical; D016896:Treatment Outcome; D014514:Ureteral Calculi / Q000601:surgery*; D020709:Ureteroscopes; D018666:Ureteroscopy / Q000379:methods*; D055815:Young Adult