Ureteric stenting outside of the operation theatre: challenges and opportunities

OBJECTIVE

To evaluate the safety, efficacy, tolerability, and cost-effectiveness of bedside or office-based ureteric stent insertion.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses-Protocols (PRISMA-P) and A MeaSurement Tool to Assess systematic Reviews (AMSTAR) 2 guidelines, we searched PubMed/the Medical Literature Analysis and Retrieval System Online (MEDLINE), the Excerpta Medica dataBASE (EMBASE), Google Scholar, Cochrane Central Register of Controlled Trials (CENTRAL), and Dimensions for English-language studies from 1978 to April 2023. Inclusion criteria focused on primary ureteric stent placements outside of the operating theatre (OT).

RESULTS

A total of 15 studies involving 2072 stents were included. Success rates for correctly positioned stents in bedside or office-based insertions ranged from 60% to 95.8%, with most studies reporting ≥80% success rates. Common failure reasons included impacted stones and difficulty identifying the ureteric orifice. Pain and tolerability were assessed using various methods, with validated tools indicating moderate pain levels, but most patients would undergo the procedure again under local anaesthesia. Complication rates were generally low, with minor complications such as haematuria or postoperative fever being the most common. Procedural costs were significantly lower in non-OT settings, with estimates indicating savings of up to four-fold.

CONCLUSION

Bedside or office-based ureteric stent insertion is a viable alternative to OT procedures, offering high success rates, manageable pain levels, low complication rates, and substantial cost savings. This approach is particularly advantageous in settings with limited OT access, highlighting its potential for broader adoption in urological practice. Future research should focus on standardising pain assessment methods and randomised studies.

Evaluation of Magnetic Ureteric Stents: A Systematic Review and Meta-Analysis

Magnetic ureteric stents offer a novel approach for simplifying stent removal, minimizing patient discomfort, and reducing procedural burdens. This systematic review and meta-analysis synthesized evidence from 12 studies involving 1,297 patients to evaluate the efficacy and safety of magnetic stent removal compared to conventional methods. Key outcomes included reductions in procedural pain scores, shorter removal times, and high patient satisfaction. Complication rates for magnetic stents were comparable to conventional stents, while cost analysis favored magnetic removal due to reduced resource utilization. These findings suggest magnetic stents are a safe, effective, and patient-friendly alternative. Further research with larger sample sizes is warranted to confirm these benefits.

MAGnetic REtriaval Device for Minimally Invasive Ureter Stent Removal

Purpose: To assess the effectiveness and pain intensity associated with magnetic ureteral stent removal using a retriever, without the aid of ultrasound guidance. Methods: We prospectively enrolled 100 patients who underwent retrograde rigid and flexible ureterorenoscopy with or without laser lithotripsy for ureteronephrolithiasis treatment from September 2021 to June 2023. These patients were assigned in two groups. Group 1 underwent the traditional ureteral stent insertion, while Group 2 underwent magnetic ureteral stent insertion. Both insertion and removal times were documented. The indwelling time for ureteral stents was 14 days. One group underwent stent removal via flexible cystoscopy using grasping forceps and the other group using just a magnetic retriever, without the aid of ultrasound guidance. The numeric pain rating scale, recommendation rate, and a standardized self-answered ureter stent symptoms questionnaire (USSQ) were obtained directly after stent removal. Results: Both groups presented comparable characteristics in factors such as age, body mass index, history of stone treatments, procedure type, and complication rates during and post-surgery. Time taken for ureteral stent insertion did not differ significantly between the groups (131.2 seconds for Group 1 vs 159.1 seconds for Group 2). However, the stent removal time (152.1 seconds for Group 1 vs 35.4 seconds for Group 2) and pain intensity (6 for Group 1 vs 2 for Group 2) were significantly lower for Group 2. Furthermore, five out of the six sections of the USSQ showed significantly better results for Group 2. Conclusions: The use of magnetic ureteral stents, as a safe and efficient alternative to conventional ureteral stents, not only eliminates the need for cystoscopy but also conserves resources and reduces patient discomfort.

Stent Syndrome: Does the Diameter Matter? Results of a Randomized Trial

Introduction: Double-J (DJ) ureteral stents are used for multiple purposes in urology. Even though they temporize the subsequent treatment of lithiasis, they may cause different symptoms that impact quality of life (QoL). Purpose: In this randomized trial, we assessed whether the diameter of ureteral stents has an impact on catheter-associated symptoms, and their impact on QoL. Methods: A total of 194 consecutive patients undergoing DJ insertion between December 2018 and December 2022 were prospectively enrolled and divided into three categories: 4.7F (Group 1, n = 71), 6F (Group 2, n = 65), and 7F (Group 3, n = 58). Within 1 week after the DJ placement, patients completed the validated Spanish version of the Ureteral Stent Symptoms Questionnaire. Continuous variables were compared using analysis of variance and Student's t-tests. For categorical data, the chi-square test was used. Results: In the domain of "work" and "additional problems," there were significant differences. In the "Work" domain, Group 1 presented the lower symptoms. In the domain "additional problems," patients in Group 1 were prescribed fewer antibiotics owing to low urinary tract symptoms. In question U4 about urinary incontinence, patients in Groups 2 and 3 developed these symptoms more than patients in Group 1. In the "sexual activity" domain, specifically in question S3 (the patient has ever suffered any type of pain during sexual activity?), patients with 4.7F presented lower scores than patients with larger catheters. Conclusion: DJ-related symptoms affect QoL in most cases. Smaller catheters produced significantly less urinary incontinence, faster work reincorporation, fewer symptoms related to sexual activity, and fewer catheter-related symptoms than 7F catheters. In contrast, Group 3 presented fewer outpatient visits because of symptoms related to the DJ.

Electrosprayed zein nanoparticles as antibacterial and anti-thrombotic coatings for ureteral stents

Ureteral stents are among the most frequently used human implants, with urothelium trauma, blood clots, and bacterial colonization being their main reasons for failure. In this study, berberine-loaded zein (ZB) nanoparticles with high drug encapsulation efficiency (>90 %) were fabricated via electrospray on flat and 3D stainless steel structures. Physico-chemical characterization revealed that the ZB nanoparticles created a highly hydrophilic, antioxidant, and scratch-resistant continuous coating over the metal structure. Results showed that the drug release rate was faster at neutral pH (i.e., PBS pH 7.4) than in an artificial urine medium (pH 5.3) due to the different swelling behavior of the zein polymeric matrix. In vitro evaluation of ZB particles onto human dermal fibroblasts and blood cells demonstrated good cell proliferation and enhanced anti-thrombotic properties compared to bare stainless steel. The ability of the electrosprayed zein particles to resist bacterial adherence and proliferation was evaluated with Gram-negative (Escherichia coli) bacteria, showing high inhibition rates (-29 % and -46 % for empty and berberine-loaded particles, respectively) compared to the medical-grade metal substrates. Overall, the proposed composite coating fulfilled the requirements for ureteral applications, and can advance the development of innovative biocompatible, biodegradable, and antibacterial coatings for drug-eluting stents.

Antistricture Ureteral Stents with a Braided Composite Structure and Surface Modification with Antistenosis Drugs

The present work describes the development of a drug-loaded ureteral stent with antistricture function based on a trilayer design in which the middle layer was braided from biodegradable poly(p-dioxanone) (PDO) monofilament. Antistenosis drugs rapamycin and paclitaxel were loaded into a silk fibroin (SF) solution and coated on the inner and outer layers of the braided PDO stent. The cumulative release of rapamycin and paclitaxel was sustained over 30 days, with a total release above 80%. The drug-loaded ureteral stents inhibited the proliferation of fibroblasts and smooth muscle cells in vitro. Subcutaneous implantation in rats showed that the drug-loaded ureteral stents were biocompatible with durable mechanical properties in vivo, revealing the inhibition of an excessive growth of fibroblasts and excessive deposition of collagen fibers. In conclusion, the dual-drug-loaded biodegradable ureteral stents show the possibility for treatment of ureteral strictures and avoid the occurrence of complications such as inflammation and restricture.

Safety and effectiveness of magnetic ureteric stent removal under ultrasound control: a randomized single center trial

PURPOSE

To assess the safety and effectiveness of magnetic ureteric stent removal with a special magnet retriever under ultrasound guidance.

METHODS

A total of 60 male patients, who underwent ureteroscopy from October 2020 to March 2022, were prospectively enrolled and randomized into two groups. Group A patients underwent conventional double-J (DJ) stent insertion and subsequent stent removal via flexible cystoscopy. Group B patients underwent stent insertion using magnetic ureteric stent [Blackstar, Urotech (Achenmühle, Germany)] and stents were removed using a special magnet retriever under ultrasound guidance. Stents were left in situ for 30 days in both groups. All patients had follow-ups with a ureter stent symptoms questionnaire at 3- and 30-days post stent insertion. Visual analog scale (VAS) was assessed immediately after stent removal.

RESULTS

Stent removal time (142.5 s vs 142.5 s, group A vs group B, p < 0.0001) and VAS scores (4 vs 1, group A vs group B, p = 0.0008) were significantly lower in Group B. There were no statistically significant differences between both groups in the "urinary symptoms" (p = 0.3471) and "sexual matters" (p = 0.6126) in the USSQ domains. There was marginal statistical significance favoring Group A in the "body pain" (p = 0.0303), "general health score" (p = 0.0072), "additional problems" (p = 0.0142), and "work performance" (p < 0.0001) domains.

CONCLUSIONS

Magnetic ureteric stent can be considered as a safe and efficient alternative to conventional DJ stent. This approach avoids the need for cystoscopy, saving resources while minimizing patient discomfort.

Stents in Veterinary Medicine

Stenting in veterinary medicine has been a rapidly growing method of interventional surgery for several years. This procedure is usually performed in the respiratory and urinary tracts, but there are cases of stenting of blood vessels or gastrointestinal structures. It is based on maintaining the permeability of a given tubular structure, thus allowing the passage of gas or liquid. This procedure is often performed as a first-line treatment in situations where pharmacological agents do not work and as an alternative method, often cheaper than the classically performed ones. There are also cases where stenting is used as a palliative treatment, e.g., to enable defecation in colonic obstruction due to tumour infiltration of the colon wall. Stenting is often a life-saving or comfort-improving procedure for animals, but one should also be aware of possible postoperative complications and be prepared for any adversity. For this reason, this review provides an insight into the current knowledge in veterinary medicine about stenting and the consequences associated with this procedure.

Impact of Ureteral Stent Material on Stent-related Symptoms: A Systematic Review of the Literature

Context

Ureteral stents are essential implants that are used on a daily basis. Since their invention, advances in stent design have been directed towards alleviating stent-related symptoms. It remains unclear how the material composition of the stent affects stent-related symptoms.

Objective

To review the literature and define the clinical impact of ureteral stent material on stent-related symptoms.

Evidence acquisition

A literature search of the Embase, MEDLINE (PubMed), and Web of Science databases was conducted on December 17, 2021 to collect articles comparing stent composition materials regarding stent-related symptoms. Thirteen publications met the inclusion criteria, of which only one met the high-quality requirements of the Cochrane Collaboration tool for assessing the risk of bias in randomized trials.

Evidence synthesis

Most trials, including the highest quality trial, seem to support that silicone double-J (DJ) stents reduce stent-related symptoms compared to nonsilicone DJ stents. Regarding physical properties, it seems that "soft" or "flexible" DJ stents reduce stent-related symptoms. However, since there was only one high-quality study with a low risk of bias, it is impossible to draw a definitive conclusion owing to the lack of quality data.

Conclusions

Silicone DJ stents, and by extension "soft" DJ stents, appear to reduce stent-related symptoms compared to nonsilicone polymers and "hard" DJ stents. No definitive conclusion can be drawn owing to a lack of quality evidence. Creating a standard for measuring and reporting physical stent properties should be the first step for further research.

Patient summary

A ureteral stent is a small hollow tube placed inside the ureter to help urine drain from the kidney. We reviewed the literature on the impact of stent material on stent-related symptoms. We found that silicone may reduce stent-related symptoms, but no definitive conclusion can be drawn and further studies are needed.

Silicone vs. Polyurethane Stent: The Final Countdown

Ureteric stents are conventionally used in daily urological practice. There is ongoing debate on the superiority of different stent materials, particularly in terms of patient tolerance. We conducted a literature review to compare silicone stents and stents made of other materials from a patient tolerability perspective. We conclude that silicone stents are better tolerated but further research is required.

Developments in Ureteral Stent Technology

Ureteral stents have been utilized for decades in maintaining ureteral patency, most commonly after ureteroscopy in the treatment of urolithiasis. Since their initial development, ureteral stents have had many technological advances that have allowed for better patient outcomes with improvements in comfort, durability, patency, encrustation resistance, biocompatibility, ease of insertion, migration, and biofilm development. Several new ureteral stents enter the market every year, each with their own touted benefits. It is essential to understand the different advantages for each ureteral stent to provide the best available care to patients when possible. The purpose of this review is to give a brief history of ureteral stent development and summarize the recent developments in ureteral stent designs. We aim to review the data supporting the clinical advantages of the latest ureteral stents available for use by urologists.

Safely increasing nephro-ureteric stent exchange intervals, resulting in significant cost savings for the interventional radiology suite, a 2-year experience in a tertiary referral centre

Aim

To evaluate the nephro-ureteric stent (NUS) insertion and exchange practice in a tertiary referral cancer centre, and determine the safety and compliance with current guidelines. We also reviewed if increasing exchange time interval from 6 to 12 weeks was safe, and if this could be adopted into our local guidelines.

Methods

A retrospective review was performed covering 24 months from January 2017 to December 2018. All NUS insertions and exchanges performed in that period were analysed, including the number of exchanges the patient underwent, the time between subsequent exchanges, and the screening time. We also reviewed the indications for stent insertion, possible causes for failed stent exchange, and factors which led to significant delays in stent exchanges for some patients. A scatterplot of screening time versus time in situ was derived and correlation analysis performed using the Pearson coefficient.

Results

Thirty-two patients underwent de novo NUS insertion during the period, and 102 NUS exchanges were performed. The interval between stent exchanges ranged from 1 to 40 weeks, with a mean of 12.3 weeks (SD = 8.96 weeks). Screening time ranged from 33 s to 17 min, with a mean of 3 min 50 s (SD = 3 min 35 s). There were 100 successful exchanges, and two failed exchanges, accounting for 1.9% of total exchanges. In both failed cases, the reason for failed exchange was due to a prolonged period between exchanges (6 months in both cases). The reason for delay for stent exchange was due to non-attendance for scheduled appointments. There was a weakly positive correlation coefficient of 0.06 (screening time versus time period between insertions); however, this was not statistically significant (p = 0.81).

Conclusion

In this retrospective review, we have demonstrated that the recommended 6-week period between stent exchanges is unnecessary in the vast majority of cases, and that a longer interval between NUS exchanges, e.g. 8–12 weeks, is safe for the patient, and reduces screening time. This reduction in procedures also provides a significant potential saving to the radiology department in both monetary expense and limited angiography suite time.

Silicone-hydrocoated ureteral stents encrustation and biofilm formation after 3-week dwell time: results of a prospective randomized multicenter clinical study

OBJECTIVE

To explore the risk of encrustation and biofilm formation for silicone ureteral stents compared to percuflex polymer stents, through a randomized multicenter study.

PATIENTS AND METHODS

Design, setting and participants: A Multicenter, prospective, randomized, single blind, comparative study of hydrocoated silicone stent (Coloplast Imajin^® hydro) versus Percuflex™ Plus stent (Boston Scientific), in 141 patients treated by flexible URS for a kidney stone. The study had ethical committee approval in the respective hospitals. Outcome measurements and statistical analysis: Endpoints related to encrustation were biofilm formation and mineral encrustation after a period of 3-week indwelling time. They were evaluated at removal through a scoring scale of ureteral stents encrustation, infrared spectroscopy and optical microscopy of inner and outer surfaces of tips, angles and along the stent's body. Comparison was performed using ANOVA.

RESULTS

119 stents were available after removal for analysis, 56 in the silicone and 63 in the Percuflex TM Plus group. Mean dwelling duration was 21.8 days for silicone, 22.1 days for PercuflexTM Plus. There was significantly more biofilm on Percuflex™ Plus compared to silicone (1.24 ± 0.08 vs 0.93 ± 0.09, p = 0.0021), and more mineral encrustation (1.22 ± 0.10 vs 0.78 ± 0.11, p = 0.0048), respectively.

CONCLUSIONS

This multicenter randomized study shows that silicone-hydrocoated stents are less prone to encrustation than PercuflexTM Plus after a 3-week dwelling period and confirms the low encrustation potential of silicone.

Long-Term Follow-Up of Yearly Replaced Double Internal Stents for Extrinsic Malignant Ureteral Obstruction

Introduction: To assess long-term outcomes of double internal stents (DIS) for the relief of external malignant ureteral obstruction (MUO). Materials and Methods: DIS (7F each; 12-month indwelling time) were inserted under general anesthesia in 62 consecutive patients (75 renal units) with MUO during 2007-2018. Surveillance was performed every 3 months, and stents were exchanged routinely every year. The need for permanent stent retrieval was considered stent failure. Maintenance of stent patency and disease-specific survival (DSS) were estimated (Kaplan-Meier). Risk factors were also assessed (univariate and multivariable Cox regression analyses). Results: The median follow-up was 27 months (interquartile range [IQR] 20-27). The most frequent tumors causing obstruction were colorectal and ovarian cancers. Six patients (10%) had stent failure caused by sepsis, creatinine elevation, or hematuria. The average time to failure was 15 months (range 1-27). A history of radiation and an estimated glomerular filtration rate (eGFR) ≤45 mL/(min/1.73 m²) were associated with stent failure (p = 0.038 and p = 0.001, respectively). Thirty-nine patients died with a median DSS of 21 months (IQR 8.6-not reached). Multivariate analysis identified eGFR ≤60 mL/(min/1.73 m²) (hazard ratio [HR] 2.1, 95% confidence interval [CI] 1.1-4.2, p = 0.02) and need for balloon dilation (HR 2.1, 95% CI 1.1-4.1, p = 0.02) as independent predictors for disease-related mortality. Twenty-six patients (42%) had stent-related complications, for example, irritative symptoms, hematuria, and infections, of whom only two failed. Conclusions: One-year indwelling DIS provide effective long-term relief of MUO and represent a simple and effective alternative to other methods of urinary diversion. They avoid the need for external tubes and contribute to improved patient satisfaction.

Comparison of cost of care for tethered versus non-tethered ureteric stents in the management of uncomplicated upper urinary tract stones

BACKGROUND

Many surgeons use a stent after ureteroscopic lithotripsy (URSL). For short-term stenting purposes, a surgeon has the choice of either a tethered or a non-tethered stent. Stents may be associated with complications that entail an additional cost to their use. There is a paucity of data on the direct healthcare cost of using stent type after either primary or secondary URSL.

METHODS

We retrospectively reviewed medical records for patients who underwent URSL for uncomplicated urolithiasis between January 2013 and December 2013 at two tertiary referral hospitals. Costs data was sourced from the costing department with complete data available for 134 patients. The overall medical care cost was estimated by computing the cost of surgery, stent-related emergency department presentations, re-admissions and stent removal.

RESULTS

A total of 113 patients had tethered stents and 21 had non-tethered stents, with similar age and gender composition between the two groups and complications rates. The mean cost of URSL and stent placement was A$3071.7 ± A$906.8 versus A$3423.8 ± A$808.4 (P = 0.049), mean cost of managing complications was A$309.4 ± A$1744.8 versus A$31.3 ± A$98.9 (P = 0.096), mean cost of out-patient clinic stent removal was A$222.5 ± A$60 versus A$1013.6 ± A$75.4 (P < 0.001) for endoscopic stent removal, overall mean cost of care was A$3603.6 ± A$1896.7 versus A$4468.1 ± A$820.8 (P = 0.042) for tethered and non-tethered stents, respectively.

CONCLUSION

It is cheaper to use a tethered ureteric stent compared with non-tethered stents for short-term stenting after uncomplicated URSL, with a mean cost saving of A$864.5.

Preparation, degradation and in vitro release of ciprofloxacin-eluting ureteral stents for potential antibacterial application

Drug-eluting stents with biodegradable polymers as reservoirs have shown great potential in the application of interventional therapy due to their capability of local drug delivery. Herein, poly(l-lactide-co-ε-caprolactone) (PLCL) with three different compositions as carriers for ciprofloxacin lactate (CIP) was coated on ureteral stents by the dipping method. To simulate a body environment, degradation behavior of PLCL as both the bulk film and the stent coating was evaluated in artificial urine (AU, pH6.20) respectively at 37°C for 120days by tracing their weight/Mn loss, water absorption and surface morphologies. Furthermore, the release profile of the eluting drug CIP on each stent exhibited a three-stage pattern, which was greatly affected by the degradation behavior of PLCL except for the burst stage. Interestingly, the degradation results on both macroscopic and molecular level indicated that the release mechanism at stage I was mainly controlled by chain scission instead of the weight loss or morphological changes of the coatings. While for stage II, the release profile was dominated by erosion resulting from the hydrolysis reaction autocatalyzed by acidic degradation residues. In addition, ciprofloxacin-loaded coatings displayed a significant bacterial resistance against E. coli and S. aureus without obvious cytotoxicity to Human foreskin fibroblasts (HFFs). Our results suggested that PLCL copolymers with tunable degradation rate as carriers for ciprofloxacin lactate could be used as a promising long-term antibacterial coating for ureteral stents.

Rethinking of ureteral stent removal using an extraction string; what patients feel and what is patients' preference? : a randomized controlled study

BACKGROUND

Ureteral stent removal using an extraction string is advantageous because it can obviate an invasive cystoscopy, but there is a paucity of data on how patients feel about it, and how bothersome or beneficial it is. We performed this study to evaluate patients' preference for stent removal using an extraction string and which parameters could affect it.

METHODS

In total, 114 consecutive patients undergoing ureteral stent insertion after ureteroscopic stone removal (URS) for unilateral recurrent ureter stones were enrolled. Patients were randomized to a string group or a no string group. Stent removal was performed on the first visit within 7 days postoperatively. All patients were asked to complete the ureteral stent symptom questionnaire, to rate the degree of pain during stent removal using a visual analog scale (VAS) and to answer to questions regarding their preference.

RESULTS

No significant differences were found in domain total scores including urinary symptoms (p = 0.17), pain (p = 0.62), general health (p = 0.37), work performance (p = 0.41). However, regarding separate questions for 'dysuria' and 'difficulties with heavy physical activity', there were significant intergroup differences (p = 0.03 and p = 0.04, respectively). Particular, a significantly higher proportion of patients in the string group checked 'stoppage of sexual intercourse due to stent-related problems' than in the no string group (p = 0.03). VAS score on stent removal was significantly higher in the no string group than the string group (p = 0.005). Among the patients who remember the experience of an indwelling ureteral stent in the past, 85% (17/20) of the no string group answered 'No' to the question of 'difference between the methods used in this time and in the past'. On the contrary, 84.2% (16/19) answered 'Yes' to the same question in the string group. And, all 16 patients of the string group who noted differences between the methods preferred ureteral stent removal using an extraction string to the past method.

CONCLUSIONS

Despite of minor increased morbidity related to the extraction string, patients preferred ureteral stent removal using the extraction string after URS. The patients with the extraction string felt less pain on stent removal than flexible cystoscopic stent removal.

TRIAL REGISTRATION

KCT0001700 . The trial was registered in the Clinical Research Information Service (CRiS), Republic of Korea; registration date: 18/11/2015.

Encrustation of the Ureteral Double J Stent in Patients with a Solitary Functional Kidney - a Case Report

INTRODUCTION

The efficacy of ureteric stents in the management of various urological conditions causing the upper urinary tract obstruction has been extensively proven, and their contribution to urology remains enormous. The clinical use of ureteric stents is associated with several complications. "Stent syndrome," encrustation, migration and urothelial hyperplasia are the most common problems related to long-term ureteral stenting.

CASE REPORT

This work presents an interesting case from our practice: a complete encrustation of a classical polyurethane double J stent two and a half months after its initial instillation, in a 70 year old man, with a solitary functioning kidney, as well as successful removal of it by using a simultaneous treatment of extracorporeal lithotripsy and ureteroscopy with a contact disintegration of encrustations and with percutaneous nephrostomy, as an auxiliary procedure for providing of additional urine derivation.

CONCLUSION

These problems can be overcome by the introduction of new advanced ureteral stent designs and biomaterials.

The use of internal stents in chronic ureteral obstruction

PURPOSE

Despite the lack of a well delineated definition, chronic ureteral obstruction imposes significant quality of life loss, increased pathological morbidity and risk of mortality as well as substantial economic burden. Ureteral stenting serves as an important therapeutic option to alleviate obstruction. Thus, we assessed the recently published literature on chronic ureteral obstruction; treatment options; types, benefits and shortcomings of current ureteral stents; as well as outcomes and complications of chronic ureteral stenting, with the goal of providing concise management guidelines.

MATERIALS AND METHODS

A systemic literature review was performed on Embase™, PubMed®, Cochrane Controlled Trials Register and Google Scholar™ on ureteral obstruction and internal ureteral stents. Relevant reviews, original research articles and their cited references were examined, and a synopsis of original data was generated on a clinically oriented basis.

RESULTS

Chronic ureteral obstruction can be classified into compression that is either intrinsic or extrinsic to the ureteral wall, or obstruction that is of a benign or malignant origin. Patients with malignant ureteral obstruction generally have a poor prognosis and are often difficult to treat. The aim of stenting is to adequately drain the upper urinary tracts while minimizing hospitalization and the negative impact on quality of life. Facing the challenge of chronic ureteral obstruction, novel stents with new compositions, materials, coatings and designs have been developed. Metallic stents are emerging as efficacious and financially viable alternatives. Early stent related complications include iatrogenic injury, stent migration or patient discomfort, while late complications include infection, difficulties with stent exchange, hardware malfunction, infection and stent encrustation.

CONCLUSIONS

Stenting in chronic ureteral obstruction is a complex and challenging problem. Much work is being done in this area and many options are being explored.

Drug-eluting metallic stents in urology

Drugeluting metal stents (DESs) have been extensively used in coronary and vascular disease. This type of stents has been proven to provide significantly lower restenosis rates due to the reduction of neo-intimal hyperplasia in comparison to the traditionally used bare metal stents (BMSs). The latter stents have been evaluated for more than a decade in urological practice in an attempt to provide permanent relief of urethral or ureteral obstruction. Although the initial results were promising, long-term experience revealed significant complications, which are mainly attributed to stent-related hyperplastic reaction compromising stent patency. The favorable experience of vascular DESs led to the application of DESs in both the urethra and ureter of animal models. These experimental results demonstrated a reduction of hyperplastic reaction of DESs in comparison to BMSs. Nevertheless, clinical data are currently not available. Considering the fact that DESs are under continuous development, the use of DESs in urology holds promise for the future and seems to be an intriguing field.

Optical coherence tomography provides images similar to histology and allows the performance of extensive measurements of drug-eluting metal stents in animal ureters

Optical coherence tomography (OCT) images and histology images of metal stents (MSs) inserted in animal ureters were compared, and the reliability of an OCT-based automated method for the performance of quantitative evaluation of ureteral MSs was evaluated. A zotarolimus-eluting metal stent (ZES) and a bare metal stent (BMS) were inserted in each ureter of ten pigs and six rabbits. OCT was performed in unobstructed stented ureters. Histopathologic examination of the stented ureters embedded in glycol-methacrylate took place. Quadrants of OCT images were compared to their respective histologic images by employing two independent observers who delineated different layers in the quadrants of OCT images and correlated them to the respective histologic quadrants. Manual (integrated OCT device software) and automated measurements of the OCT images using an automated strut detection method were compared. The observers highly agreed on the delineation of urothelium from the lamina propria and the lamina propria from the muscle layer of the ureteral wall. The algorithm measurements were similar to the manual measurements, and the algorithm proved to be reliable in the evaluation of ureteral MSs. Significantly higher endothelial hyperplasia of the BMSs in comparison to the ZESs was also quantitatively demonstrated by the strut detection method. OCT proved to be a reliable method for the evaluation of ureteral MSs. OCT provided images of the stented ureteral lumen similar to light microscopy quality. Measurements of the stented ureter are reliably performed by the automated strut detection method.

Braided thin-walled biodegradable ureteral stent: preliminary evaluation in a canine model

OBJECTIVES

To evaluate a novel designed degradable ureteral stent.

METHODS

A total of 24 male Beagles, each with bilateral stents implanted (a biodegradable ureteral 4.5-Fr stent and a standard 4-Fr biostable stent) were divided into four groups. Intravenous pyelography, B-mode ultrasonography, and blood and urine tests were carried out before the procedure (0 weeks), and at 1-, 2-, 3- and 4-week intervals. Meanwhile, the mechanical characteristics of stents were tested, and scanning electron microscopy images of the biodegradable braided stents were obtained at different time-points postoperatively. In addition, histopathological changes were compared between the two different stents.

RESULTS

All biodegradable braided stents began degrading at 1 week, and had completely degraded by 4 weeks. Hydronephrosis was equivalent during the first 2 weeks, but less with the biodegradable stents than with the control biostable stents at 3 and 4 weeks. Preoperative and postoperative blood and urine results were similar. The mechanical properties of the biodegradable stents were better than conventional biostable stents. Scanning electron microscopy images obtained at different weekly intervals showed that stents degraded in a predictable fashion. Histological testing of the urinary tract showed that the stent-related tissue reactivity of the two different stents were similar.

CONCLUSIONS

Our novel braided thin-walled biodegradable stents provide temporary renal drainage as good as commercially available biostable stents. They also have good biocompatibility and physical characteristics. Therefore, they might have clinical application.

Comparison of a biodegradable ureteral stent versus the traditional double-J stent for the treatment of ureteral injury: an experimental study

Ureteral injury remains a major clinical problem; here we developed a biodegradable ureteral stent and compared its effectiveness with a double-J stent for treating ureteral injury. Eighteen dogs with injured ureters were subdivided into two groups. In group A, one injured ureter was treated with a biodegradable stent, whereas only end-to-end anastomosis was performed on the other side. In group B, one injured ureter was treated with a biodegradable stent, while a double-J stent was used on the other side. Intravenous urography, radioactive renography, histological examinations, scanning electron microscopy (SEM) and elemental composition analysis were performed at 40, 80 and 120 days postoperatively. Results showed that the biodegradable stent could effectively prevent hydronephrosis and hydroureter secondary to ureteral injury. Moreover all biodegradable stents gradually degraded and discharged completely in 120 days. SEM and elemental composition analysis of the surface of the double-J stent confirmed calcification at 80 days and calcific plaque at 120 days, while no signs of calcification were found in the biodegradable stent group. Histological studies found no difference between the biodegradable stented ureters and double-J stented ureters. It is concluded that the biodegradable ureteral stent was more advantageous than the double-J stent for treating ureteral injury in a canine model.

Evaluation of zotarolimus-eluting metal stent in animal ureters

BACKGROUND AND PURPOSE

Drug-eluting stents proved to minimize neointimal hyperplasia in coronary vessels. Hyperplastic reaction is the most common unwelcome event related to the use of metal mesh stents in the ureter. We evaluated the effect of zotarolimus-eluting stent (ZES) Endeavor Resolute in the porcine and rabbit ureter.

MATERIALS AND METHODS

A ZES and a bare metal stent (BMS) were inserted in each ureter of 10 pigs and 6 rabbits. The insertion was performed by the retrograde approach. CT was used for the evaluation of porcine ureters while intraoperative intravenous urography (IVU) was used for rabbit ureters. The follow-up included CT or IVU every week for the following 4 weeks for pigs and 8 weeks for rabbits. Renal scintigraphies were performed before stent insertion and during the third week in all animals. Optical coherence tomography (OCT) has been used for the evaluation of the luminal and intraluminal condition of the ureters with stents. Histopathologic examination of the these ureters embedded in glycol-methacrylate was performed.

RESULTS

Hyperplastic reaction was present in both stent types. BMSs in seven porcine ureters were completely obstructed while porcine ureters with ZES stents had hyperplastic tissue that did not result in obstruction. Two rabbit ureters with BMS stents were occluded while no ZES was associated with ureteral obstruction. The function of the seven porcine renal units and the two rabbit units with obstructed ureters with stents was compromised. The OCT revealed increased hyperplastic reaction in the ureters with BMS stents in comparison with those with ZESs. Although, hyperplastic reaction was present in all cases, pathologic examination revealed significantly more hyperplastic reaction in BMSs.

CONCLUSION

ZESs in the pig and rabbit ureter were not related to hyperplastic reaction resulting in stent occlusion. These stents were related to significantly lower hyperplastic reaction in comparison with BMSs while inflammation rates were similar for both stent types.

Clinical experience with ureteral metal stents

Ureteral metal stents (MSs) present a minimally invasive tool to preserve the drainage of renal pelvis whenever ureteral patency is at risk to be obstructed due to extrinsic or intrinsic etiologies. Clinical experience with these stents demonstrates that they impose a promising alternative treatment option in ureteral pathologies that are difficult to be treated via common polymeric stents. Current application of MSs in the treatment of both benign and malignant ureteral obstruction reveals quite promising results. Nevertheless, the ideal MS that would provide uncomplicated long-term effectiveness is still lucking and current MS usage is facing several adverse effects between which stent obstruction, encrustation, infection, migration, and patient discomfort. Ongoing attempts to create more inert stent with sophisticated novel designs are expected to improve current MS efficiency. MSs will play a major role in the future as a routine management of a variety of ureteral pathologies.

New combined approach in metallic ureteral stenting to avoid urothelial hyperplasia: study in swine model

PURPOSE

We assessed the therapeutic value of a new treatment option for ureteral strictures that may avoid urothelial hyperplasia, which is the main cause of metallic stent failure.

MATERIALS AND METHODS

We used 24 pigs in this study. An experimental model of ureteral stricture was induced in all animals. Obstruction was confirmed by ultrasound and retrograde ureteropyelogram 6 weeks after model creation. The pigs were then randomly allocated to 2 experimental groups. Therapy involved placement of a 6 × 30 mm metallic ureteral covered stent in the ureteral stricture in group 1 and subsequent endoureterotomy at the ureteral segments adjacent to the 2 ends of the stent in group 2. A double pigtail stent was then deployed for 3 weeks. Completion studies 6 months after therapy included retrograde ureteropyelogram, endoluminal ultrasound and ureteroscopy to assess urothelial hyperplasia formation.

RESULTS

At the end of the study evidence of urothelial hyperplasia was seen in 50% of the pigs in group 1 and in 29% in group 2. Four and 2 cases of cranial stent migration in groups 1 and 2, respectively, were seen at 6 months. Hyperplasia and renal involvement were statistically significantly different between the groups with more damage in group 1 than in group 2.

CONCLUSIONS

Hyperplasia was markedly reduced when ureteral peristalsis was inhibited by endoureterotomy at the area of interaction between the stent and the ureter.

New biodegradable drug-eluting stents for urethral strictures in a rabbit model

In this study, the feasibility and the effect of a new biodegradable drug-eluting urethral stents for the treatment of urethral stricture in a rabbit model were evaluated, and the biocompatibility properties of the new biodegradable drug-eluting urethral stents in the rabbit urethral assessed. A total of 34 male New Zealand White rabbits with urethral strictures were used, and equally divided into two groups: with drug stents and drug-free stents. The urethral strictures were made by using a self-control explosion device as the control. Stents were surgically implanted into the stenotic urethras of rabbits under direct vision. Reparative effects, including biocompatibility assessment, were evaluated by urethroscopy, retrograde urethrography, and histology at different intervals at weeks 4, 8, and 12. Although retrograde urethrography and urodynamic results at 12 weeks showed no comparable differences among the three groups, urethroscopic and histological follow-up indicated that the drug stents had minimized the stent-related inflammatory responses, urothelial hyperplasia, and scar formation compared with the drug-free stents. The new biodegradable paclitaxel-eluting stents were more biocompatible and effective for treating urethral strictures in the rabbit model than the drug-free stents.

Ureteral stents: new ideas, new designs

Ureteral stents represent a minimally invasive alternative to preserve urinary drainage whenever ureteral patency is deteriorated or is under a significant risk to be occluded due to extrinsic or intrinsic etiologies. The ideal stent that would combine perfect long-term efficacy with no stent-related morbidity is still lacking and stent usage is associated with several adverse effects that limit its value as a tool for long-term urinary drainage. Several new ideas on stent design, composition material and stent coating currently under evaluation, foreseen to eliminate the aforementioned drawbacks of ureteral stent usage. In this article we review the currently applied novel ideas and new designs of ureteral stents. Moreover, we evaluate potential future prospects of ureteral stent development adopted mostly by the pioneering cardiovascular stent industry, focusing, however, on the differences between ureteral and endothelial tissue.