ABSTRACT
PURPOSE: 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). MATERIALS AND 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.
