BERKELEY, CA (UroToday.com) - In our recent study published in PLOS ONE, we investigated the fluid dynamic field in a ureter after insertion of a double-J stent. This method represents the most common clinical procedure to restore urine drainage in obstructed ureters. Nevertheless, ureter stenting causes side effects, and bacterial adhesion and encrustation of crystals over the stent surface are often responsible for stents’ failure. In particular, the side holes of the stent have been identified as potential anchoring sites for encrusting deposits, and analysis of double-J stents retrieved from patients revealed plugging of side holes with crystals.
Our study aimed at providing quantitative insights, using an engineering-based approach, into the governing fluid dynamic mechanisms that can potentially cause stents to fail. We built an artificial transparent model of the ureter resembling its natural anatomy (i.e., from measurements on pig ureters) and we investigated the effect of different parameters (e.g., severity of ureteric obstruction, urine viscosity, and flow rate) on kidney pressure. Due to the transparency of the model, in situ flow visualisation in proximity of stent’s side holes was also conducted. The following conclusions of clinical interest were drawn:
- The stent itself introduces a significant reduction of the ureteric inner lumen which may be noxious for kidney functionality, particularly in the long term. Urologists should thus consider with care the decision for a ureteric stent implant, since the additional hydraulic resistance generated by the stent should be counterbalanced by the advantage of providing a stable path for urine drainage.
- Laminar vortices were found in proximity of stent’s side holes. The presence of vortices in the extra-luminal space of the stent may cause entrapment of crystals and/or bacteria. This mechanism may encourage the aggregation of particles and adhesion to the stent surface, particularly in proximity of stent side holes, as observed on stents retrieved from patients.
- The artificial ureter can potentially represent a training platform used by urologists for optimising the procedure of stent placement, or by industries for testing new stent designs, materials, surface treatments, etc.
On-going work is focusing on the development of a second-generation of ureteric models capable of mimicking the bladder compartment and ureteric distensibility more faithfully. Using the developed model, the effect of fluid dynamic parameters on biofilm and encrustation dynamics will be investigated in the near future.
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Written by:
Francesco Clavica,1 Marcus J. Drake,2 Xunli Zhang,3 and Dario Carugo4 as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
1Department of Urology, sector FURORE, Erasmus MC, Rotterdam, The Netherlands ; Bioengineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom ; Bristol Urological Institute, Southmead Hospital, Bristol, United Kingdom.
2Bristol Urological Institute, Southmead Hospital, Bristol, United Kingdom ; School of Clinical Science, University of Bristol, Bristol, United Kingdom.
3Bioengineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom ; Institute for Life Sciences, University of Southampton, Southampton, United Kingdom.
4Bioengineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom ; Electro-Mechanical Engineering, Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom.
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