Tong Jimmy C K, Sparrow Ephraim M, Abraham John P
Laboratory for Heat Transfer and Fluid Flow Practice, Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
J Biomech Eng. 2007 Apr;129(2):187-92. doi: 10.1115/1.2472381.
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.
当支架植入堵塞的输尿管时，从肾脏流向膀胱的尿液必须经过一条非常复杂的流动路径。该路径由两条平行通道组成，其中一条是支架的内腔，另一条是支架外表面与输尿管内壁之间的环形空间。沿着支架长度分布的众多通孔使流动路径更加复杂。这些孔允许尿液在环形空间和内腔之间通过。由于用于固定支架的螺旋“猪尾”包含多个流体进出端口，尿液流动模式进一步复杂化。本文首次使用数值模拟对带支架输尿管内的流体流动进行了定量分析。此处获得的数值解充分揭示了整个带支架输尿管内尿液流动的细节。研究发现，在没有堵塞的情况下，大多数通孔不起作用。此外，每个螺旋猪尾中只有最靠近支架本体的端口积极参与尿液流动。只有在由于结垢或生物污染可能出现堵塞的情况下，众多通孔才会被激活。数值模拟能够追踪尿液通过通孔以及在堵塞物附近的流动情况。模拟还能够为肾脏到膀胱的尿液流速提供高度准确的结果。本文提出的模拟方法构成了未来合理设计输尿管支架的强大新工具。
