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Jeong JY, Cho KS, Jun DY, Moon YJ, Kang DH, Jung HD, Lee JY. Impact of Preoperative Ureteral Stenting in Retrograde Intrarenal Surgery for Urolithiasis. MEDICINA (KAUNAS, LITHUANIA) 2023; 59:medicina59040744. [PMID: 37109702 PMCID: PMC10145251 DOI: 10.3390/medicina59040744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 03/26/2023] [Accepted: 04/05/2023] [Indexed: 04/29/2023]
Abstract
Background and Objectives: Ureteral stent insertion passively dilates the ureter. Therefore, it is sometimes used preoperatively before flexible ureterorenoscopy to make the ureter more accessible and facilitate urolithiasis passage, especially when ureteroscopic access has failed or when the ureter is expected to be tight. However, it may cause stent-related discomfort and complications. This study aimed to assess the effect of ureteral stenting prior to retrograde intrarenal surgery (RIRS). Materials and Methods: Data from patients who underwent unilateral RIRS for renal stone with the use of a ureteral access sheath from January 2016 to May 2019 were retrospectively analyzed. Patient characteristics, including age, sex, BMI, presence of hydronephrosis, and treated side, were recorded. Stone characteristics in terms of maximal stone length, modified Seoul National University Renal Stone Complexity score, and stone composition were evaluated. Surgical outcomes, including operative time, complication rate, and stone-free rate, were compared between two groups divided by whether preoperative stenting was performed. Results: Of the 260 patients enrolled in this study, 106 patients had no preoperative stenting (stentless group), and 154 patients had stenting (stenting group). Patient characteristics except for the presence of hydronephrosis and stone composition were not statistically different between the two groups. In surgical outcomes, the stone-free rate was not statistically different between the two groups (p = 0.901); however, the operation time for the stenting group was longer than that of the stentless group (44.8 ± 24.2 vs. 36.1 ± 17.6 min; p = 0.001). There were no differences in the complication rate between the two groups (p = 0.523). Conclusions: Among surgical outcomes for RIRS with a ureteral access sheath, preoperative ureteral stenting does not provide a significant advantage over non-stenting with respect to the stone-free rate and complication rate.
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Affiliation(s)
- Jae Yong Jeong
- Department of Urology, National Health Insurance Service Ilsan Hospital, Goyang 10444, Republic of Korea
| | - Kang Su Cho
- Department of Urology, Prostate Cancer Center, Gangnam Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul 06273, Republic of Korea
| | - Dae Young Jun
- Department of Urology, Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Young Joon Moon
- Department of Urology, Kyungpook National University Hospital, Kyungpook National University School of Medicine, Daegu 41944, Republic of Korea
| | - Dong Hyuk Kang
- Department of Urology, Inha University College of Medicine, Incheon 22332, Republic of Korea
| | - Hae Do Jung
- Department of Urology, Inje University Ilsan Paik Hospital, Inje University College of Medicine, Goyang 10380, Republic of Korea
| | - Joo Yong Lee
- Department of Urology, Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
- Center of Evidence Based Medicine, Institute of Convergence Science, Yonsei University, Seoul 03722, Republic of Korea
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Vogt B. Investigating the encrustation of reinforced ureteral stents by computational flow dynamic simulations. World J Urol 2023; 41:1451-1457. [PMID: 36930252 DOI: 10.1007/s00345-023-04356-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Accepted: 02/26/2023] [Indexed: 03/18/2023] Open
Abstract
PURPOSE In cases of extrinsic ureteral obstruction, obstruction due to encrustation is particularly detrimental to functioning of the stent. A thorough understanding of the causes that lead to stent encrustation is essential. Computational fluid dynamic (CFD) simulations may provide a reliable screening platform for investigating the interplay between flow processes and encrustation dynamics in stents. METHODS Using a tailor-made program, we attempted to evaluate a number of reinforced ureteral stents by CFD simulations with an obstructed or unobstructed ureter and steady or discontinuous flow patterns to identify critical regions with abrupt changes in shape susceptible to stagnant flow and encrustation. RESULTS For the Vortek® and Urosoft stents, the longitudinal opening of the stents confirmed the presence of critical regions. No critical region was observed for the Superglide stent. CFD simulations showed that cavities formed near the critical regions represented patently stagnant flow and were potentially susceptible to the formation of encrusting deposits. Encrustations were greater in the obstructed design than in the unobstructed design. In the model with a suddenly interrupted laminar flow, the peristaltic motion resulted in new discontinuous encrustation areas scattered throughout the entire external and internal surface of the stent. CONCLUSION The analysis of fluid dynamics through the tested stents confirmed that encrustations are possible in regions of stagnant flow and showed that stent models with the smoothest possible surface are preferable. The discontinuous flow model provided results that are closer to the findings observed in the clinic and should be more often integrated into CFD simulations.
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Affiliation(s)
- Benoît Vogt
- Department of Urology, Polyclinique de Blois, 1 Rue Robert Debré, 41260, La Chaussée Saint-Victor, France.
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Zheng S, Obrist D, Burkhard F, Clavica F. Fluid mechanical performance of ureteral stents: The role of side hole and lumen size. Bioeng Transl Med 2023; 8:e10407. [PMID: 36925692 PMCID: PMC10013766 DOI: 10.1002/btm2.10407] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 07/22/2022] [Accepted: 08/16/2022] [Indexed: 01/05/2023] Open
Abstract
Ureteral stents are indispensable devices in urological practice to maintain and reinstate the drainage of urine in the upper urinary tract. Most ureteral stents feature openings in the stent wall, referred to as side holes (SHs), which are designed to facilitate urine flux in and out of the stent lumen. However, systematic discussions on the role of SH and stent lumen size in regulating flux and shear stress levels are still lacking. In this study, we leveraged both experimental and numerical methods, using microscopic-Particle Image Velocimetry and Computational Fluid Dynamic models, respectively, to explore the influence of varying SH and lumen diameters. Our results showed that by reducing the SH diameter from 1.1 to 0.4 mm the median wall shear stress levels of the SHs near the ureteropelvic junction and ureterovesical junction increased by over 150 % , even though the flux magnitudes through these SH decreased by about 40 % . All other SHs were associated with low flux and low shear stress levels. Reducing the stent lumen diameter significantly impeded the luminal flow and the flux through SHs. By means of zero-dimensional models and scaling relations, we summarized previous findings on the subject and argued that the design of stent inlet/outlet is key in regulating the flow characteristics described above. Finally, we offered some clinically relevant input in terms of choosing the right stent for the right patient.
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Affiliation(s)
- Shaokai Zheng
- ARTORG Center for Biomedical Engineering Research, Faculty of Medicine University of Bern Bern Switzerland
| | - Dominik Obrist
- ARTORG Center for Biomedical Engineering Research, Faculty of Medicine University of Bern Bern Switzerland
| | - Fiona Burkhard
- Department of Urology Inselspital, Bern University Hospital, University of Bern Bern Switzerland
| | - Francesco Clavica
- ARTORG Center for Biomedical Engineering Research, Faculty of Medicine University of Bern Bern Switzerland.,Department of Urology Inselspital, Bern University Hospital, University of Bern Bern Switzerland
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Zheng S, Amado P, Obrist D, Burkhard F, Clavica F. An in vitro bladder model with physiological dynamics: Vesicoureteral reflux alters stent encrustation pattern. Front Bioeng Biotechnol 2022; 10:1028325. [PMID: 36304894 PMCID: PMC9592728 DOI: 10.3389/fbioe.2022.1028325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 09/22/2022] [Indexed: 11/22/2022] Open
Abstract
In vitro models are indispensable to study the physio-mechanical characteristics of the urinary tract and to evaluate ureteral stent performances. Yet previous models mimicking the urinary bladder have been limited to static or complicated systems. In this study, we designed a simple in vitro bladder model to simulate the dynamics of filling and voiding. The physio-mechanical condition of the model was verified using a pressure-flow test with different bladder outlet obstruction levels, and a reflux test was performed to qualitatively demonstrate the stent associated vesicoureteral reflux (VUR). Finally, the setup was applied with and without the bladder model to perform encrustation tests with artificial urine on commercially available double-J stents, and the volumes of luminal encrustations were quantified using micro-Computed Tomography and image segmentation. Our results suggest that, VUR is an important factor contributing to the dynamics in the upper urinary tract with indwelling stents, especially in patients with higher bladder outlet obstruction levels. The influence of VUR should be properly addressed in future in vitro studies and clinical analyses.
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Affiliation(s)
- Shaokai Zheng
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
- *Correspondence: Shaokai Zheng,
| | - Pedro Amado
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
| | - Dominik Obrist
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
| | - Fiona Burkhard
- Department of Urology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Francesco Clavica
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
- Department of Urology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Computational simulation of the flow dynamic field in a porous ureteric stent. Med Biol Eng Comput 2022; 60:2373-2387. [PMID: 35763188 PMCID: PMC9294020 DOI: 10.1007/s11517-022-02620-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 06/15/2022] [Indexed: 11/04/2022]
Abstract
Ureteric stents are employed clinically to manage urinary obstructions or other pathological conditions. Stents made of porous and biodegradable materials have gained increasing interest, because of their excellent biocompatibility and the potential for overcoming the so-called ‘forgotten stent syndrome’. However, there is very limited characterisation of their flow dynamic performance. In this study, a CFD model of the occluded and unoccluded urinary tract was developed to investigate the urinary flow dynamics in the presence of a porous ureteric stent. With increasing the permeability of the porous material (i.e., from 10−18 to 10−10 m2) both the total mass flow rate through the ureter and the average fluid velocity within the stent increased. In the unoccluded ureter, the total mass flow rate increased of 7.7% when a porous stent with permeability of 10−10 m2 was employed instead of an unporous stent. Drainage performance further improved in the presence of a ureteral occlusion, with the porous stent resulting in 10.2% greater mass flow rate compared to the unporous stent. Findings from this study provide fundamental insights into the flow performance of porous ureteric stents, with potential utility in the development pipeline of these medical devices.
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