title: Flow characteristics of 3 unique ureteral stents: investigation of a Poiseuille flow pattern.
abstract: OBJECTIVE
  The pattern of flow in the stented ureter (intraluminal and/or extra luminal) has only been defined for the standard pigtail stent. No data are available on stent flow for any specialty stents. To our knowledge we present the first investigation characterizing the type of flow through a stent (Poiseuille versus nonPoiseuille flow).
  
  
  METHODS
  Flow was measured in an unstented ureter, a standard 7Fr double pigtail stent and the 7/3Fr Tail stent, 7Fr Spirastent and 14/7Fr endopyelotomy stent using a previously developed stent flow model. In vitro pressure flow studies were also done in nonfenestrated 14/7Fr, Tail and standard 7Fr stents. These stents were infused at a constant flow rate of 2 to 10 ml. per minute with monitoring of the corresponding pressure gradients. Resistance to flow was determined for these stents using pressure flow plots and Poiseuille's law.
  
  
  RESULTS
  In vivo the 7Fr pigtail, 14/7Fr endopyelotomy and 7/3Fr Tail stents had statistically similar flow rates. Flow through each of these stents exceeded the flow through an unstented ureter. The Spirastent had the least flow in all categories tested. There was no correlation of Poiseuille flow parameters measured in vitro for nonfenestrated stents with in vivo stent flow.
  
  
  CONCLUSIONS
  In stented ureters fluid drains through and around the stent regardless of its design. The flow characteristics of these 3 specialty stents were not predictable according to lumen or stent size. In vitro Poiseuille's flow did not correlate with in vivo stent flow.
authors.affiliation: Division of Urologic Surgery, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: E O
authors.initials: EO
authors.lastname: Olweny
authors.forename: A J
authors.initials: AJ
authors.lastname: Portis
authors.forename: J S
authors.initials: JS
authors.lastname: Afane
authors.forename: A V
authors.initials: AV
authors.lastname: Brewer
authors.forename: A L
authors.initials: AL
authors.lastname: Shalhav
authors.forename: K
authors.initials: K
authors.lastname: Luszczynski
authors.forename: E M
authors.initials: EM
authors.lastname: McDougall
authors.forename: R V
authors.initials: RV
authors.lastname: Clayman
mesh_terms: D000818:Animals; D004867:Equipment Design; D008961:Models, Structural; D011312:Pressure; D015607:Stents; D013556:Swine, Miniature; D014513:Ureter / Q000502:physiology; D014563:Urodynamics