Ureteral stents: the good the bad and the ugly

Advances in ureteral stent technology

PURPOSE OF REVIEW

Ureteral stents are an invaluable tool for urologists but suffer from several drawbacks, including: limited durability due to stent encrustation, significant morbidity from bothersome urinary symptoms, pain and infection, risk of the forgotten stent and costly removal. This review highlights key advances in ureteral stent technology that seek to address these issues.

RECENT FINDINGS

Over the past 2 years clinical trials have brought ureteral stent technology aimed to reduce stent-associated morbidity closer to clinical application. Stent material and changes to stent design show promise in improving patient tolerability without increasing complications. Low-tech innovations such as magnetic and catheter snare removal may quickly reduce costs. Radical advances such as biodegradable stent materials remain in preclinical models but show promise for eliminating the need for stent removal.

SUMMARY

The ideal ureteral stent does not currently exist in clinical practice. This review highlights key studies that have advanced ureteral stent technology in the past 2 years.

The accumulation of particles in ureteric stents is mediated by flow dynamics: Full-scale computational and experimental modeling of the occluded and unoccluded ureter

Ureteric stents are clinically deployed to restore urinary drainage in the presence of ureteric occlusions. They consist of a hollow tube with multiple side-holes that enhance urinary drainage. The stent surface is often subject to encrustation (induced by crystals-forming bacteria such as Proteus mirabilis) or particle accumulation, which may compromise stent's drainage performance. Limited research has, however, been conducted to evaluate the relationship between flow dynamics and accumulation of crystals in stents. Here, we employed a full-scale architecture of the urinary system to computationally investigate the flow performance of a ureteric stent and experimentally determine the level of particle accumulation over the stent surface. Particular attention was given to side-holes, as they play a pivotal role in enhancing urinary drainage. Results demonstrated that there exists an inverse correlation between wall shear stress (WSS) and crystal accumulation at side-holes. Specifically, side-holes with greater WSS levels were those characterized by inter-compartmental fluid exchange between the stent and ureter. These "active" side-holes were located either nearby ureteric obstructions or at regions characterized by a physiological constriction of the ureter. Results also revealed that the majority of side-holes (>60%) suffer from low WSS levels and are, thus, prone to crystals accumulation. Moreover, side-holes located toward the proximal region of the ureter presented lower WSS levels compared to more distal ones, thus suffering from greater particle accumulation. Overall, findings corroborate the role of WSS in modulating the localization and extent of particle accumulation in ureteric stents.

Analysis of long-term effect of ureteral balloon dilatation combined with internal and external drainage tube in the treatment of benign ureteral stricture

Purpose

There are few reports about balloon dilatation combined with internal and external drainage tube in the treatment of ureteral stricture under interventional therapy. The aim of the study is to explore the safety, effectiveness and long-term efficacy of this treatment strategy.

Materials and methods

It is a retrospective and observational study. From October 2013 to October 2016, 42 patients with benign lower ureteral stricture received interventional treatment. Balloon dilatation combined with internal and external drainage tube implantation were used. There were 25 male patients and 17 female patients. There were 7 cases (16.7%) with congenital ureteral stricture, 12 cases (28.6%) with inflammation, 15 cases (35.7%) with ureteral stricture after lithotomy or lithotripsy, and 8 cases (19.0%) with ureteral stricture after pelvic or abdominal surgery. After the drainage tube was removed, B ultrasound, enhanced CTU or IVP of urinary system were reexamined every six months. The follow-up time was 12–60 months.

Results

The age was 52.9 ± 11.6 years. The length of ureteral stricture was 1.1 ± 0.5 cm. 42 patients completed interventional treatment, the technical success rate was 100%, no ureteral perforation, rupture or other complications were identified. Preoperative urea nitrogen 9.2 ± 2.3 mmol/L and creatinine 175.8 ± 82.8umol/L. Urea nitrogen and creatinine were 3.8–9.1 mmol/L and 45.2–189.6 umol/L when removing the drainage tube. There were significant differences in the levels of urea nitrogen and creatinine before and after tube removal (P < 0.05). The ureteral patency rate was 100% at 6 months, 93% at 12 months, 83% at 18 months, 79% at 24 months, 76% at 30 months and 73% at 36–60 months. The overall success rate was 73%. Multivariate Cox regression analysis showed that stenosis length was a risk factor for postoperative patency (P < 0.05).

Conclusion

Balloon dilatation combined with internal and external drainage tube implantation in the treatment of benign lower ureteral stricture is safe and effective.

Efficacy of the novel, innovative, single-use grasper integrated flexible cystoscope for ureteral stent removal: A systematic review

BACKGROUND

We aimed to define the published impact, efficacy, cost-effectiveness and precise role of the Isiris-α device: the world's first sterile, single-use grasper integrated flexible cystoscope (SUGIFC) for ureteral stent removal.

METHODS

After PROSPERO registration (CRD42021228755), the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines were utilized. The search terms "Grasper Integrated Flexible Cystoscope," and "Isiris," within the following databases: PubMed, Scopus, Cochrane Library, Web of Science and EMBASE were searched.

RESULTS

In this review, a cumulative total experience (10 publications) included 970 "SUGIFC" procedures (755 patients). However, only 366/970 procedures were actually used for "ureteral stent removal," with the remainder being surveillance cystoscopy only (603/970) or foreign body retrieval (1/970). Procedure-related and device failures in planned "removal of ureteral stents," was reported in 8/366 (346 patients) and 1/366 (346 patients), respectively. The cost-benefit utilizing the SUGIFC device is advantageous compared to "in-theatre" stent removals and favours less busy centres where maintenance, repair and replacement costs are more relevant. Other listed benefits include shorter stent indwelling times, shorter procedure duration, lower rates of bacteriuria and urinary tract infections, fewer emergency department visits and lower readmission rates. Technical limitations include the absence of an independent working channel, a narrower visual field and the lack of image universality since the monitor is device-specific.

CONCLUSION

The SUGIFC device needs to be outweighed against local costs and individual health systems. Its application in ambulatory ureteral stent removal may become significant due to the accessibility and convenience that it offers the attending urologist.

Success rate of repeat flexible ureteroscopy following previous failed access: An analysis of stent duration

INTRODUCTION

Approximately 8% of patients that undergo therapeutic or diagnostic ureteroscopy will have the procedure aborted and ureter stented due to failed access. The primary objective of this study was to assess mean stent duration prior to repeat ureteroscopy and to calculate the associated successful access rate.

METHODS

This retrospective, descriptive study evaluated all patients undergoing interval ureteroscopy following a failed procedure by endourologic surgeons at the University of Alberta from 2016-2018. Patients declining interval ureteroscopy, or those with malignant/known ureteral strictures were excluded from the study. The primary outcome measures were median time to salvage ureteroscopy and the rate of successful access of the repeat procedure.

RESULTS

A total of 119 patients were identified as having a failed ureteroscopy during our study period. First-time and recurrent stone formers accounted for 64 (53.8%) and 47 (39.5%) patients, respectively. Median stent duration to second procedure was 17 days (average 20, range 10-84). Most patients had their repeat ureteroscopy at 14 days or greater (81.5%); 22 (18.5%) patients had their repeat ureteroscopy between 10 and 13 days. The success rate of a second ureteroscopy after stenting was 99.2% (118/119).

CONCLUSIONS

Ureteric stenting following failed ureteroscopy leads to exceedingly high rates of successful access at interval procedure (99.2%). The standard duration of ureteric stenting employed at our institution is two weeks. Of the patients that underwent an accelerated second procedure (between 10-13 days of stenting), all had successful access at their interval procedure.

Strategies to Improve Patient Outcomes and QOL: Current Complications of the Design and Placements of Ureteric Stents

Ureteric stents have played a vital role in relieving urinary obstruction in many urological conditions. Although they are extremely successful, stents have been associated with complications and reduced patients' health-related quality of life (HRQoL). There are many factors that may affect the quality and longevity of stents. In this review, we have highlighted the journey and innovation of ureteric stents through the modern day. A literature review was conducted to identify relevant articles over the last 20 years. There is a plethora of evidence with various indications for the use of ureteral stents and how they affect QoL. There is still ongoing research to develop the ideal stent with reduced encrustation, one that resists infection and is also comfortable for the patients. Stents made from metal alloys, polymers and biodegradable materials have unique properties in their own right but also have certain deficiencies. These have been discussed along with an overview of newly developed stents. Certain pharmacological adjuncts have also been highlighted that may be useful to improve patient's tolerance to stents. In summary, this paper describes the features of the different types of stents and the problems that are frequently encountered, including effect on patients' HRQoL and financial burden to healthcare providers.