Comparison of the Removal Efficiency and Safety of Magnetic Versus Conventional Ureteral Stents: A Systematic Review and Meta-analysis.

Context: The incidence of urolithiasis is increasing year by year. Ureteral stents are a popular treatment option for this condition. Efforts to improve the material and structure of stents to increase comfort and reduce complications have led to the introduction of magnetic stents. Objective: To evaluate differences in removal efficiency and safety for magnetic and conventional stents. Evidence acquisition: This study was conducted and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Data were extracted according to the PRISMA principles. We collected and combined data from randomized controlled trials on magnetic versus conventional stents to evaluate the efficiency of their removal and the associated effects. Data synthesis was performed using RevMan 5.4.1 and heterogeneity was evaluated using I2 tests. A sensitivity analysis was also performed. Key metrics included the stent removal time, Visual Analog Scale (VAS) pain scores, and Ureteral Stent Symptom Questionnaire (USSQ) scores for various domains. Evidence synthesis: Seven studies were included in the review. We found that magnetic stents had a shorter removal time (mean difference [MD] -8.28 min, 95% confidence interval [CI] -15.6 to -0.95; p = 0.03) and their removal was associated with less pain (MD -3.01 points, 95% CI -3.83 to -2.19; p < 0.01) in comparison to conventional stents. USSQ scores for urinary symptoms and sexual matters were higher for magnetic than for conventional stents. There were no other differences between the stent types. Conclusions: Magnetic ureteral stents have the advantages of a shorter removal time, less pain during removal, and low cost in comparison to conventional stents. Patient summary: For patients undergoing treatment of urinary stones, a thin tube called a stent is often temporarily inserted in the tube between the kidney and the bladder to allow stones to pass. Magnetic stents can be removed without any need for a second surgical procedure. Our review of studies comparing two types of stents suggests that magnetic stents are superior to conventional stents in terms of efficiency and comfort during removal.

A systematic review of magnetic versus conventional ureteric stents for short term ureteric stenting.

Ureteric stents play an essential role in urology. However, patients can suffer a range of stent-related symptoms with stent in situ and during removal. Conventional ureteric stents are removed using a flexible cystoscopy, whereas magnetic stents may be rapidly removed with a smaller catheter-like retrieval device. The primary aim of this systematic review was to compare the morbidity including pain associated with conventional versus magnetic ureteric stents. The secondary aim was cost comparison. Searches were performed across databases, including Medline, Scopus, Embase and Cochrane. This review was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The search from the 5 databases returned a total of 358 articles. After duplicates were removed as well as the inclusion and exclusion criteria applied, a total of 6 studies were included in the final review. Ureteric Stent Symptoms Questionnaire (USSQ) and Visual Analogue Score (VAS) were used in most of the studies. All the studies reported that magnetic ureteric stents resulted in a reduction in the pain on the removal of magnetic ureteric stents, and no statistically significant difference with indwelling ureteric stents. Furthermore, majority of the studies reported a reduction in the cost associated with magnetic ureteric stents. There is no significant difference in pain from indwelling ureteric stents. There is a reduction in pain with the removal of magnetic ureteric stents compared to conventional removal via cystoscopy and an associated reduction in cost.

Feasibility and safety of magnetic-end double-J ureteral stent insertion and removal in children.

PURPOSE: The need for surgical removal of a double-J ureteral stent (DJUS) is considered one of its disadvantages. Apart from increased cost, repeated exposure to general anesthesia is a concern in children. Alternative techniques have been described, all failing to become integrated into mainstream practice. Stents with a distal magnetic end, although introduced in the early 1980s, have only recently gained acceptance. We report the feasibility and safety of insertion and removal of a magnetic-end double-J ureteral stent (MEDJUS) in a pediatric population. MATERIALS AND METHODS: We retrospectively analyzed the use of the Magnetic Black-Star Urotech® MEDJUS between 11/2016 and 12/2019 in children. Stents were removed in the outpatient clinic using a transurethral catheter with a magnetic tip. RESULTS: MEDJUS insertion was attempted in 100 patients (65 boys). Mean age was 7.8 years (0.5-18). The stent was placed in an antegrade procedure (n = 47), by a retrograde route (n = 10), and during open surgery (n = 43). Stent insertion was successful in 84 cases (84%). All 16 failures occurred during the antegrade approach in laparoscopic pyeloplasty, with inability to push the stent and its magnet through the ureterovesical junction in 14. Magnetic removal was attempted in 83 patients, successful in 81 (98%). There was no added morbidity with the MEDJUS. CONCLUSIONS: The use of MEDJUS is a safe and effective strategy that obviates the need for additional general anesthesia in children. Its insertion is similar to that with regular DJUS, and its easy and less time-consuming removal benefits both the patient and the hospital and validates its clinical use.

Ureteric stenting with magnetic retrieval: an alternative to traditional methods.

INTRODUCTION: Ureteric stents are frequently placed following endo-urological procedures. These stents cause significant morbidity for patients. Standard ureteric stents are removed by flexible cystoscopy. This procedure can be unpleasant for patients and requires additional resources. A newly designed magnetic stent allows removal in an outpatient setting. The aim of our study is to compare the magnetic stent and standard ureteric stents with regard to morbidity, pain on stent removal and cost-effectiveness. METHODS: This study was carried out across two sites between September 2016 and July 2017. In site A, a magnetic stent (Urotech, Black-Star®) is removed by magnetic retrieval device. Fifty consecutive patients completed the validated Ureteric Stent Symptom Questionnaire (USSQ) and visual analogue scale (VAS) at the time of stent removal. On site B, a soft polyurethane stent (Cook Universa) was removed by flexible cystoscopy. Fifty patients were identified retrospectively and completed questionnaires by post. Cost analysis was also performed. RESULTS: One hundred questionnaires were included for analysis. No significant difference in stent morbidity as assessed by the USSQ was shown between both groups. Median duration of stenting was significantly shorter in the magnetic stent group (5.5 versus 21.5 days, p < 0.001). Mean pain on stent removal was significantly less with magnetic retrieval (2.9 versus 3.9, p < 0.05). Complication rates were similar in both groups. Cost analysis showed a cost saving of €203 per patient with the magnetic stent group. CONCLUSION: Magnetic stents cause similar morbidity for patients compared with standard stents removed by flexible cystoscopy; they are associated with less pain at removal and are cost saving.

Nanoparticle-Mediated Cell Capture Enables Rapid Endothelialization of a Novel Bare Metal Stent.

Incomplete endothelialization of intracoronary stents has been associated with stent thrombosis and recurrent symptoms, whereas prolonged use of dual antiplatelet therapy increases bleeding-related adverse events. Facilitated endothelialization has the potential to improve clinical outcomes in patients who are unable to tolerate dual antiplatelet therapy. The objective of this study was to demonstrate the feasibility of magnetic cell capture to rapidly endothelialize intracoronary stents in a large animal model. A novel stent was developed from a magnetizable duplex stainless steel (2205 SS). Polylactic-co-glycolic acid and magnetite (Fe3O4) were used to synthesize biodegradable superparamagnetic iron oxide nanoparticles, and these were used to label autologous blood outgrowth endothelial cells. Magnetic 2205 SS and nonmagnetic 316L SS control stents were implanted in the coronary arteries of pigs (n = 11), followed by intracoronary delivery of magnetically labeled cells to 2205 SS stents. In this study, we show extensive endothelialization of magnetic 2205 SS stents (median 98.4% cell coverage) within 3 days, whereas the control 316L SS stents exhibited significantly less coverage (median 48.9% cell coverage, p < 0.0001). This demonstrates the ability of intracoronary delivery of magnetic nanoparticle labeled autologous endothelial cells to improve endothelialization of magnetized coronary stents within 3 days of implantation.

Computational modeling of magnetic nanoparticle targeting to stent surface under high gradient field.

A multi-physics model was developed to study the delivery of magnetic nanoparticles (MNPs) to the stent-implanted region under an external magnetic field. The model is firstly validated by experimental work in literature. Then, effects of external magnetic field strength, magnetic particle size, and flow velocity on MNPs' targeting and binding have been analyzed through a parametric study. Two new dimensionless numbers were introduced to characterize relative effects of Brownian motion (BM), magnetic force induced particle motion, and convective blood flow on MNPs motion. It was found that larger magnetic field strength, bigger MNP size, and slower flow velocity increase the capture efficiency of MNPs. The distribution of captured MNPs on the vessel along axial and azimuthal directions was also discussed. Results showed that the MNPs density decreased exponentially along axial direction after one-dose injection while it was uniform along azimuthal direction in the whole stented region (averaged over all sections). For the beginning section of the stented region, the density ratio distribution of captured MNPs along azimuthal direction is center-symmetrical, corresponding to the center-symmetrical distribution of magnetic force in that section. Two different generation mechanisms are revealed to form four main attraction regions. These results could serve as guidelines to design a better magnetic drug delivery system.

In vitro study on the feasibility of magnetic stent hyperthermia for the treatment of cardiovascular restenosis.

Thermal treatment or hyperthermia has received considerable attention in recent years due to its high efficiency, safety and relatively few side-effects. In this study, we investigated whether it was possible to utilize targeted thermal or instent thermal treatments for the treatment of restenosis following percutaneous transluminal coronary angioplasty (PTCA) through magnetic stent hyperthermia (MSH). A 316L stainless steel stent and rabbit vascular smooth muscle cells (VSMCs) were used in the present study, in which the inductive heating characteristics of the stent under alternative magnetic field (AMF) exposure, as well as the effect of MSH on the proliferation, apoptosis, cell cycle and proliferating cell nuclear antigen (PCNA) expression of the rabbit VSMCs, were evaluated. The results demonstrated that 316L stainless steel coronary stents possess ideal inductive heating characteristics under 300 kHz AMF exposure. The heating properties were shown to be affected by the field intensity of the AMF, as well as the orientation the stent axis. MSH had a significant effect on the proliferation and apoptosis of VSMCs, and the effect was temperature-dependent. While a mild temperature of 43°C demonstrated negligible effects on the growth of VSMCs, MSH treatment above 47°C effectively inhibited the VSMC proliferation and induced apoptosis. Furthermore, a 47°C treatment exhibited a significant and long-term inhibitory effect on VSMC migration. The results strongly suggested that MSH may be potentially applied in the clinic as an alternative approach for the prevention and treatment of restenosis.

Expressions of matrix metalloproteinases and tissue inhibitor of metalloproteinases after bare and magnetic stent implantation in rabbits / 老年心脏病学杂志（英文版）

Objective We aimed to investigate whether magnetic stent has preventive effect on in-stent restenosis by observing expressions of matrix metalioproteinase (MMP)2,MMP9,tissue inhibitor of matrix metalloproteinase (TIMP)1 and TIMP2 after balloon angioplasty,bare and magnetic stent implantation in rabbits.Methods Rabbits underwent balloon angioplasty,bare and magnetic stent implantation in the left iliac arteries.The changes of MMPs and TIMPs were examined at various time points in the injured arteries using the methods of zymography,Western blot analysis,reverse transcription-polymerase chain reaction (RT-PCR) and morphometric analysis.Results Balloon angioplasty group (BA) and magnetic stent group (MS) showed lower intrinsic gelatinolytic activity and higher expression of TIMPs with less intimae hyperplasia;Whereas bare stent (BS) group exhibited higher intrinsic gelatinolytic activity and lower expression of TIMPs with significant intimae hyperplasia.Conclusion Magnetic stent probably has preventive effect on in-stent restenosis by changing intrinsic matrix metalloproteinases activity and expression of TIMPs.