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TECHNICAL PAPERS: Fluids/Heat/Transport

Numerical Simulation of the Urine Flow in a Stented Ureter

[+] Author and Article Information
Jimmy C. K. Tong, Ephraim M. Sparrow

Laboratory for Heat Transfer and Fluid Flow Practice, Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455

John P. Abraham

Laboratory for Heat Transfer and Fluid Flow Practice, School of Engineering, University of St. Thomas, St. Paul, MN

J Biomech Eng 129(2), 187-192 (Aug 21, 2006) (6 pages) doi:10.1115/1.2472381 History: Received July 28, 2005; Revised August 21, 2006

When a stent is implanted in a blocked ureter, the urine passing from the kidney to the bladder must traverse a very complicated flow path. That path consists of two parallel passages, one of which is the bore of the stent and the other is the annular space between the external surface of the stent and the inner wall of the ureter. The flow path is further complicated by the presence of numerous pass-through holes that are deployed along the length of the stent. These holes allow urine to pass between the annulus and the bore. Further complexity in the pattern of the urine flow occurs because the coiled “pig tails,” which hold the stent in place, contain multiple ports for fluid ingress and egress. The fluid flow in a stented ureter has been quantitatively analyzed here for the first time using numerical simulation. The numerical solutions obtained here fully reveal the details of the urine flow throughout the entire stented ureter. It was found that in the absence of blockages, most of the pass-through holes are inactive. Furthermore, only the port in each coiled pig tail that is nearest the stent proper is actively involved in the urine flow. Only in the presence of blockages, which may occur due to encrustation or biofouling, are the numerous pass-through holes activated. The numerical simulations are able to track the urine flow through the pass-through holes as well as adjacent to the blockages. The simulations are also able to provide highly accurate results for the kidney-to-bladder urine flow rate. The simulation method presented here constitutes a powerful new tool for rational design of ureteral stents in the future.

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Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Computer-drawn image of a stented ureter

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Figure 2

Combined volumetric flow rates in the bore and the annulus for the cases identified in Table 1

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Figure 3

Streamwise variations of the bore, annulus, and combined (total) flow rates for cases 2 and 4

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Figure 4

Streamwise variations of the bore, annulus, and combined (total) flow rates for case 3

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Figure 5

Streamwise variations of the bore, annulus, and combined (total) flow rates for case 5

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Figure 6

Streamwise variations of the bore, annulus, and combined (total) flow rates for case 7

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Figure 7

Flow patterns for case 2: (a) Annulus to bore at the first pass-through holes, (b) stand off at an intermediate pass-through hole, and (c) bore to annulus at the last pass-through hole

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Figure 8

Flow pattern adjacent to a very small blockage in the annulus of case 4

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Figure 9

Flow pattern due to a large blockage in the bore of case 5: (a) At the pass-through hole just upstream of the blockage, (b) adjacent to the blockage, and (c) at the pass-through hole just downstream of the blockage

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