Latest advancements in ureteral stent technology

Polyvinylpyrrolidone hydrogel coating for ureteral stent: Safety and performance evaluation

BACKGROUND

Ureteral stents are commonly used in urology. However, complications such as encrustation and infection on the surface of the stent, and injury to the ureteral mucosa can occur after implantation, causing discomfort for patients.

OBJECTIVE

We intend to confirm the biosafety of polyvinylpyrrolidone (PVP) hydrophilic coating and its lubrication properties for surface modification of ureteral stents to reduce friction and improve patient comfort.

METHODS

Based on our previous studies, we have developed a PVP hydrophilic coating for surface modification of ureteral stents. We firstly investigated the cytotoxicity, intradermal irritation, delayed type hypersensitivity, and acute systemic reactions of stent coating extracts. We further characterized the break strength, retention strength, and dynamic friction of the stent.

RESULTS

The cell survival rate of all experimental groups was greater than 70%. No hypersensitivity reaction, systemic toxicity reaction, or obvious intradermal reaction were observed. The above results indicate that the test results of the modified stent meet the requirements of ISO 10993-5: 2009 (Cytotoxicity); ISO 10993-10:2021 (Sensitization and Irritation); ISO 10993-11:2017 (Acute Systemic Toxicity). After soaking in artificial urine for an extended period, there was no obvious change in its super-slip performance.

CONCLUSION

Our results confirm the safety and lubrication characteristics of PVP hydrophilic coating for ureteral stent surface modification. The performance of this coating has the potential to reduce complications after stent implantation, thereby improving patient comfort, reducing medical burden, and has a good clinical application prospect.

Double J Stents and Reno-Ureteral Lithiasis: Dynamic Changes in Management during the COVID-19 Pandemic

PURPOSE

To provide an evidence-based review of the use of ureteral stents in managing reno-ureteral lithiasis during the COVID-19 pandemic.

MATERIALS AND METHODS

A literature search was conducted between 2020 and 2023 using the PubMed and SCOPUS databases. As a part of the search query, we entered "ureteral stents" OR "double J stent" AND "renal colic" OR "ureteral obstruction" OR "reno-ureteral lithiasis" AND "COVID-19 Pandemic" OR "SARS-CoV-2 infection".

RESULTS

Patients with lithiasis should be categorized into low priority, intermediate priority, high priority, and emergency under the COVID-19 pandemic scenario to manage their delay and save resources, including healthcare professionals, beds, and ventilators. However, immediate interventions are necessary for individuals at risk of life-threatening septic complications. During the COVID-19 pandemic, the feasibility of conducting or resuming elective activity depended on local circumstances, the accessibility of beds and ventilators, and the execution of screening protocols. If lithiasis surgery is delayed, consequences and increased effort will be inevitable. It is possible that teleconsultation could help guide these patients and cut down on unnecessary visits and exposure.

CONCLUSIONS

COVID-19 has shifted treatment options for urinary stones, with ureteral stents being a safe, efficient, and cost-effective option for managing urolithiasis. Decompression is essential in emergency situations, while ureteral stents reduce the risk of infection and hospital visits.

Comparison of Ureteral Stent Biomaterials: Encrustation Profile in Lithogenic Artificial Urine Models

Ureteral stent encrustation significantly limits indwelling time and can lead to downstream urological problems. However, no ideal polymeric biomaterials have been shown to completely resist encrustation in long-term urine exposure. Recently, 2-hydroxyethyl methacrylate (HEMA)-coated Pellethane was reported as a promising biomaterial resistant to encrustation. This study compared HEMA-coated Pellethane to commercially available stents under two different artificial urine environments. To evaluate the degree and composition of encrustation on HEMA-coated Pellethane, Boston Scientific Tria, Bard InLay Optima, Cook Universa Hydrogel, and Cook Black Silicone stents were used at various dwelling times in two different artificial urine environments. In a batch-flow model, samples of stents were suspended in an artificial urine solution (AUS) at 37 °C. Every 24 h for 11 weeks, 50% of the AUS would be replaced with fresh components using a programmable peristaltic pump system. The stent materials were removed at suitable time intervals and air-dried for 24 h under sterile conditions before follow-up analysis. SEM was used to assess the degree of encrustation, and inductively coupled plasma mass spectrometry (ICP-MS) was employed to quantify the encrusted compositions, specifically for calcium, magnesium, and phosphorus. We measured the weight gain over time due to encrusted deposits on the stents and quantified the amount of Ca, Mg, and P deposited on each encrusted stent. After the 11 week trial, HEMA-coated Pellethane showed the most average mass change. SEM showed that HEMA-coated Pellethane was fully encrusted in just 2 weeks in the AUS environments, and ICP-MS showed that Ca is the most abundant deposit. Among all the tested stents, Black Silicone performed the best. The two AUSs were formulated to encrust more rapidly than physiological conditions. HEMA-coated Pellethane is not an ideal stent material, while silicone is a promising material for advancing ureteral stents.

Ureteral stenting in the clinic: a safe and cost-effective alternative to the operating room

PURPOSE

Ureteral stent placement is one of the most common procedures performed by urologists, and is typically done in the operating room. At Ochsner-LSU Health Shreveport, urologists have a unique setting allowing them to place ureteral stents for patients present in the outpatient ambulatory clinic without the need for nitrous oxide. This allows patients to avoid being admitted to the hospital and receiving subsequent general anesthesia in the operating room. Therefore, our novel study evaluates the feasibility, safety, and cost-effectiveness of ureteral stents insertion in the clinic.

MATERIAL AND METHODS

In this study, we analyzed 240 patients with a total of 279 different ureteral stent insertion encounters to evaluate the safety and costs of stenting in the clinic compared to the operating room. Stents were placed in the outpatient clinic for 126 patients, which required either a new ureteral stent insertion or a scheduled stent exchange.

RESULTS

Overall, there was an increased age and length of stent duration among those who were stented in the clinic. We did not observe any increase in narcotics use, pain, adverse injuries, or differences in stent length. The total cost of a stent insertion operating room was $16,349.91 whereas the clinic procedure cost $7,865.69, however: medicare reimbursement remained the same.

CONCLUSION

Our findings demonstrate a novel use of stenting in the clinic is feasible as an outpatient alternative. It is a safe alternative to the operating room, and more cost-effective.

A modified biodegradable mesh ureteral stent for treating ureteral stricture disease

Ureteral stricture disease (USD) is a common urologic condition. Patients with ureteral stricture disease may suffer from ipsilateral flank pain, nausea, urinary calculi, infection, and impaired renal function. The treatments of USD include surgery, followed by implantation of the ureteral stent to aid the drainage of the urine. The traditional ureteral stent may sometimes cause urological infection, encrustation, and discomfort. To decrease the complication of the ureteral stent, we modified the structure and material based on the traditional ureteral stent. The traditional nondegradable Double-J shape tubular ureteral stent was turned into the biodegradable mesh ureteral stent. The modified mesh ureteral stent and Double-J ureteral stent were inserted into the ureters of the USD animals, respectively. The results of the gross morphology, serology, urinalysis, histology, microstructure, et al. demonstrated that modified mesh ureteral stent has a favorable ability in supporting the ureter and has no effect on cell proliferation, migration, apoptosis, and cell cycle of the human uroepithelial cells. The mesh ureteral stent could relieve ureter obstruction and can be slowly biodegraded after 3-5 months of implantation without the need for a second surgery to remove the stent. Compared to the Double-J ureteral stent, the modified mesh ureteral stent has a lower rate of urinary tract infection and less encrustation. It is expected to be an alternative treatment approach for USD. However, due to the limited number of animals and clinical data, further study focused on the application value in clinical practice are essential. STATEMENT OF SIGNIFICANCE: This study demonstrates: 1. A modified biodegradable mesh ureteral stent; 2. Without the need for a second surgery to remove the stent; 3. A lower rate of urinary tract infection and less encrustation than a double-J ureteral stent; 4. An alternative treatment approach for USD.

Application, Advancement, and Complication of Ureteral Stent and Encrustation: A Major Complication

Three technological aspects have a significant impact on the functioning of an optimal stent. The substance it is made up of, model or design, and coating of the surface are important areas for research. To give recognition of an ideal stent, it summarizes some essential breakthroughs that occurred. Encrustation is a regular problem that can happen when a ureteral stent is implanted in the urinary tract, and it may be dangerous. The part of the paper covers the mechanism of encrustation, stent management, and the most recent technologies created to solve this problem. Encrustation has a complicated and diverse mechanism that includes the time it stays inside, patient-specific risk factors, controlled film production, formation of biofilm, and deposition of minerals. A number of high-tech advancements in stent substances and coverings/coatings could help to reduce the danger of encrustation of stents. It's critical to determine the amount of encrustation of a stent so that therapy options can be tailored properly. For the care of ureteral stents, which are encrusted, we offer a unique therapeutic protocol. The duration of stent indwelling time has been repeatedly established to be a critical risk factor for the evolution of encrustation. The period of stent indwelling time has consistently been established to be a critical risk element for the evolution of encrustation. Patients who are predisposed to bacteriuria and urinary lithiasis are also predisposed to encrustation. Repeated urinary tract infections, diabetes, and chronic kidney failure are among the factors that might escalate urine bacterial load, which can lead to stent encrustation. Due to the prevalence of ureteral stents in urology, it's critical to keep up to date on the best ways to prevent stent encrustation, recognize high-risk patients, and remove them using multimodal techniques.

Computational simulation of the flow dynamic field in a porous ureteric stent

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.

Case Report: A Calculus-Free Ureteral Stent Forgotten for 29 Years

Ureteral stents are widely used. If ureteral stents remain in place for extended periods, the probability of migration and stone formation increases substantially. However, a 29-year-old ureteral stent that was placed and did not develop calculus is rare. We reported a 45-year-old man admitted with pain in the left side of his waist and abdomen for more than 10 years. He underwent a ureterotomy 29 years prior to admission for left ureteral calculi, and a ureteral stent was placed postoperatively to prevent ureteral strictures. The ureteral stent was not removed in the hospital due to poor compliance on the part of the patient. This left ureteral stent was not visible on computed tomography (CT) and plain films. On ureteroscopy or flexible ureteroscopy, no new calculus was found in the left ureter and kidney. No calculus was found in the stent that is usually easily removed with calculus-removing forceps. This phenomenon is rare, and it highlights the importance of follow-up.

Biodegradable ureteral stents: in vitro assessment of the degradation rates of braided synthetic polymers and copolymers

OBJECTIVES

The control and predictability of degradation rates and the absence of obstructive phenomena are two main challenges for research regarding biodegradable ureteral stents. The objectives are to assess the degradation performance and safety of braided combinations of three synthetic biodegradable polymers and copolymers; and to evaluate the interference of a heparin dip coating on degradation and bacterial colonization.

METHODS

The hydrolysis of polyglycolic acid (PGA), poly lactic-co-glycolic acid (PLGA) and Glycomer™ 631 is assessed in this in vitro study that comprises ten groups. Stent samples present a braided arrangement and are incubated in porcine urine that undergoes analysis and exchange every 48 h until degradation. Coating is carried out with sodium heparin via dip coating and determination of the heparin release is carried out by ELISA test. Variables of study are stent mass, mass fold change, degradation time, bacterial colonization and concentration of heparin released in artificial urine.

RESULTS

There is statistical significance in degradation times between all materials except between the Glycomer™ 631 alone and combined with PGA. Mass fold change analysis of the Glycomer™ 631 evidences an increasing trend of its mass during degradation. The combination of Glycomer™ 631 and PGA presents a progressive and gradual degradation, where PGA degrades at week 3 while Glycomer™ 631 remains intact until its fragmentation at the late stage of degradation. Heparin coating has no significant impact on mean degradation times and trends in any group, nor on bacteriuria rates; heparin concentration decreases significantly after 72 h. Products of degradation are released steadily with minimum dimensions.

CONCLUSIONS

The combination of synthetic biodegradable polymers and copolymers with different degradation rates provides a gradual staged degradation. Heparin dip coating is a safe and feasible technique to coat biodegradable ureteral stents without interfering in degradation rates although it does not have a significant effect on the onset of bacterial colonization.

Impact of an Acute Care Urology Service on Timelines and Quality of Care in the Management of Nephrolithiasis

Background: The acute care surgery model has led to improved outcomes for emergent surgical conditions, but similar models of care have not been implemented in urology. Our department implemented an acute care urology (ACU) service in 2015, and the service evolved in 2018. We aimed to evaluate the impact of the ACU model on the management of nephrolithiasis. Materials and Methods: We conducted a retrospective review of all patients with urology consults in the emergency department for nephrolithiasis, who required surgical intervention from 2013 to 2019. Patients were divided into three cohorts based on date of consultation: Pre-ACU (2013-2014), Phase 1 (2015-2017), and Phase 2 (2018-2019). Results: We identified 733 patients with nephrolithiasis requiring intervention (162 pre-ACU, 334 Phase 1, and 237 Phase 2). Before ACU implementation, median time from consult to definitive intervention was 36 days. After ACU implementation, median time to intervention decreased to 22 days in Phase 1 (p < 0.001) and 15 days in Phase 2 (p < 0.001). On multivariable Cox regression, the hazard of definitive intervention improved in Phase 1 (hazard ratio [HR] 1.90, p < 0.001) and in Phase 2 (HR 1.80, p < 0.001). Rates of primary definitive intervention without initial decompression and loss to follow-up were also significantly improved, compared to the pre-ACU cohort. Conclusions: Implementation of a structured ACU service was associated with improved time to treatment for patients with acute nephrolithiasis, as well as increased primary definitive intervention and improved follow-up care. This model of care has potential to improve patient outcomes for nephrolithiasis and other acute urological conditions.

Ureteral stents cannot decrease the incidence of ureteroileal anastomotic stricture and leakage: A systematic review and meta-analysis

BACKGROUND

The ileal conduit and ileal orthotopic neobladder were the most popular methods for urinary diversion following radical cystectomy. Stenting the anastomosis of ileo-ureter or ureter-neobladder was a common practice. However, it is still controversial if ureteral stents could prevent complications such as ureteroileal anastomosis stricture (UIAS) and ureteroileal anastomosis leakage (UIAL) after ureteral anastomosis.

OBJECTIVES

This study aims to investigate the role of the ureteral stent in preventing UIAS and UIAL.

DATA SOURCES

We systematically searched the related studies in PubMed, Embase, and Cochrane Library up to June 2020.

STUDY ELIGIBILITY CRITERIA

Cohort studies that identified the use of stent and the incidence of UIAS or UIAL were recorded.

DATA SYNTHESIS

Comparative meta-analysis was conducted on four cohort studies for comparison of UIAS and UIAL between the stented and nonstented groups. Besides, eleven studies which reported the events of UIAS and UIAL were used for meta-analysis of single proportion.

RESULTS

A total of 11 studies were qualified for analysis. Comparative meta-analysis identified that the incidence of UIAS was higher in the stented group than that in the nonstented group, but this did not reach a significant difference (odds ratio [OR]: 1.64; 95% confidence interval [CI]: 0.88-3.05; P = 0.12). Besides, there was no difference in the incidences of UIAL between the stented and the nonstented groups. On meta-analysis of single proportion, the incidence of UIAS was 7% (95% CI: 3%-10%) in the stented group and 3% (95% CI: 1%-6%) in the nonstented group. The UIAL rate was 1% (95% CI, 0%-4%) in stented patients and 2% (95% CI, 1%-4%) in nonstented patients.

CONCLUSION

Stenting the ureteroileal anastomosis resulted in a higher incidence of UIAS. There is no evidence to support ureteral stents could prevent the occurrence of UIAL after urinary diversion.

A Novel Visual Grading for Ureteral Encrusted Stent Classification to Help Decide the Endourologic Treatment

Objective: The aim of the study is to propose a visual classification for encrusted stents (ESs) to help choose the appropriate endourologic treatment. Materials and Methods: A multicenter, retrospective, and descriptive study was performed. A total of 140 patients with encrusted Double-J stents were enrolled from 5 different institutions. The novel visual grading for ureteral encrusted stent (V-GUES) classification system ranges from A to D, increasing with severity of encrustation. Results: ESs could be removed with a single intervention in 112 patients (86.8%). Type A and B ESs could be removed in all patients (100% success). Type D stents had minor retrieval and stone-free rates (p = 0.006 and p < 0.0001, respectively). Flexible ureteroscopy had a low success rate (77.7%) for type C stents (odds ratio [OR]: 0.21). Combined access had a 100% success rate for retrieval of type C ESs and a 92.9% success rate for type D ESs (OR: 9.18). Type D stents were associated with patients requiring more than one session to retrieve the stent (OR: 0.11) and stones (OR: 0.21). Conclusions: The V-GUES system is associated with treatment success rates of ES retrieval and stone-free status. It is also associated with the complication rate and the number of sessions needed for patients to be stent and stone free. The V-GUES classification could help counsel patients about the best treatment options and their outcomes. Further prospective studies will be needed to provide external validation.

Does potassium citrate administration change the type and composition of encrusted material on Double-J stent compared to primary stone?

Purpose

To evaluate the effect of potassium citrate administration on the composition of encrusted material on the ureteral stent after Double-J insertion.

Methods

We designed a randomized clinical trial for our study; 65 patients that underwent transurethral lithotripsy and Double-J stent insertion were included in the study after informed consent and divided into two groups. In the first group (33 patients) potassium citrate was prescribed after surgery till stent removal and the second group (32 patients) followed without prescribing this medication. After stent removal, encrusted materials on removed stents were analyzed then the type and composition of encrusted material compared with the primary stone that was removed.

Results

Our results revealed that the type and composition of primary stone and encrusted stone were similar in patients that do not receive potassium citrate (p-value of 0.073, 0.251 and 0.944 for calcium oxalate, uric acid, and calcium phosphate respectively). In patients that taking potassium citrate rate of calcium oxalate (p-value < 0.001) and uric acid (p-value < 0.001) material on encrusted stent significantly decreased compared with the non-intervention group.

Conclusion

Results of this study revealed that taking of potassium citrate after ureteral stent insertion significantly decreases the formation of calcium oxalate and uric acid encrusted material on Double-J stent so it could be recommended for prevention of stent encrustation in patients that primary stone analysis are calcium oxalate and uric acid stone.

Analytical methods for braided stents design and comparison with FEA

Braiding technology is nowadays commonly adopted to build stent-like devices. Indeed, these endoprostheses, thanks to their typical great flexibility and kinking resistance, find several applications in mini-invasive treatments, involving but not limiting to the cardiovascular field. The design process usually involves many efforts and long trial and error processes before identifying the best combination of manufacturing parameters. This paper aims to provide analytical tools to support the design and optimization phases: the developed equations, based on few geometrical parameters commonly used for describing braided stents and material stiffness, are easily implementable in a worksheet and allow predicting the radial rigidity of braided stents, also involving complex features such as multiple twists and looped ends, and the diameter variation range. Finite element simulations, previously validated with respect to experimental tests, were used as a comparator to prove the reliability of the analytical results. The illustrated tools can assess the impact of each selected parameter modification and are intended to guide the optimal selection of geometrical and mechanical stent proprieties to obtain the desired radial rigidity, deliverability (minimum diameter), and, if forming processes are planned to modify the shape of the stent, the required diameter variations (maximum and minimum diameters).

Advancing Toward 3D Printing of Bioresorbable Shape Memory Polymer Stents

Stents have evolved significantly since their introduction to the medical field in the early 1980s, becoming widely used in percutaneous coronary interventions and following nephrological procedures. However, the current commercially available stents do not degrade and remain in the body forever, leading to problems like restenosis in cardiovascular applications or requiring removal procedures in ureteral applications. Efforts to replace metal with resorbable materials have largely been halted after the commercial failure of and safety concerns elicited by Abbott's Absorb stent in 2017. Industry continues to use common polymers such as poly(l-lactide) (PLLA) and polycaprolactone (PCL) for biomedical products, but due to the weak mechanical properties of these bioresorbable materials in comparison to metals, these devices have struggled to accomplish the goals set, increasing risk of thrombosis. 3D printing stents using bioresorbable and shape memory materials could provide a method of patient-personalized production, remove the need for balloon expansion, and limit stent migration, thus bringing a new age of stent technology. The investigation of a range of 3D-printable and bioresorbable shape-memory polymers can provide solutions to the shortcomings of previously explored bioresorbable stents and revitalize the medical device industry efforts into advancing stent technology.

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.

A Microfluidic-Based Investigation of Bacterial Attachment in Ureteral Stents

Obstructions of the ureter lumen can originate from intrinsic or extrinsic factors, such as kidney stones, tumours, or strictures. These can affect the physiological flow of urine from the kidneys to the bladder, potentially causing infection, pain, and kidney failure. To overcome these complications, ureteral stents are often deployed clinically in order to temporarily re-establish urinary flow. Despite their clinical benefits, stents are prone to encrustation and biofilm formation that lead to reduced quality of life for patients; however, the mechanisms underlying the formation of crystalline biofilms in stents are not yet fully understood. In this study, we developed microfluidic-based devices replicating the urodynamic field within different configurations of an occluded and stented ureter. We employed computational fluid dynamic simulations to characterise the flow dynamic field within these models and investigated bacterial attachment (Pseudomonas fluorescens) by means of crystal violet staining and fluorescence microscopy. We identified the presence of hydrodynamic cavities in the vicinity of a ureteric occlusion, which were characterised by low levels of wall shear stress (WSS < 40 mPa), and observed that initiation of bacterial attachment occurred in these specific regions of the stented ureter. Notably, the bacterial coverage area was directly proportional to the number of cavities present in the model. Fluorescence microscopy confirmed that the number density of bacteria was greater within cavities (3 bacteria·mm^-2) when compared to side-holes of the stent (1 bacterium·mm^-2) or its luminal surface (0.12·bacteria mm^-2). These findings informed the design of a novel technological solution against bacterial attachment, which reduces the extent of cavity flow and increases wall shear stress over the stent's surface.