title: Radially expanding single-step nephrostomy tract dilator.
abstract: OBJECTIVE
  To compare the radial and axial forces produced by balloon, Amplatz, and radially expanding single-step nephrostomy (RESN) systems and report our initial clinical results using the new RESN device. Balloon, Amplatz, and Alken dilators are commonly used to establish nephrostomy tracts in percutaneous surgery. They require multiple steps, with the potential for kinking and displacement of the working guidewire. In contrast, the new RESN tract dilator expands a unique sleeve conduit and places an Amplatz-like sheath in a single step with less dependence on a guidewire for dilation.
  
  
  METHODS
  An experimental model was designed using a perforated silicon disc with a 10F central opening to measure the axial force transmission as 30F balloon, Amplatz, and RESN systems were inserted through the silicon discs. We also report our first 9 patients who underwent percutaneous dilation with the RESN system.
  
  
  RESULTS
  Thirty French expansion was achieved with each dilator tested. Substantially lower axial forces were transmitted with the RESN device compared with the balloon and Amplatz dilators (5.2 versus 13.1 and 19.2 lb, respectively, P <0.001). Intraoperatively, all 9 patients were successfully dilated, and the kidney was relatively stationary as imaged with fluoroscopy. One patient with multiple prior renal procedures was successfully dilated with RESN system after failed attempts with balloon dilation.
  
  
  CONCLUSIONS
  The RESN dilator is a rapid, single-step access system successfully used in our first 9 patients. Intraluminal sleeve dilation eliminates guidewire dependence for maintaining access, limits renal displacement, and facilitates appropriate vector force for percutaneous dilation.
authors.affiliation: Department of Urology, University of California, San Francisco, School of Medicine, San Francisco, California, USA.
authors.forename: R Z
authors.initials: RZ
authors.lastname: Goharderakhshan
authors.forename: B F
authors.initials: BF
authors.lastname: Schwartz
authors.forename: D M
authors.initials: DM
authors.lastname: Rudnick
authors.forename: P B
authors.initials: PB
authors.lastname: Irby
authors.forename: M L
authors.initials: ML
authors.lastname: Stoller
mesh_terms: D004106:Dilatation / Q000295:instrumentation; D006801:Humans; D009403:Nephrostomy, Percutaneous / Q000295:instrumentation* / Q000379:methods