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This paper reports the first telemetric ureteral stent compatible with common placement procedure, enabling wireless sensing and detection of ureteral obstruction and resultant kidney swelling known as hydronephrosis at an early stage. This sensor-integrated "intelligent" ureteral stent is prototyped via the design and fabrication approaches that raise the practicality of the device and tested in a harvested swine kidney-ureter model ex vivo. Leveraging a polymeric double-J stent and micro-electro-mechanical systems technology, the intelligent stent is built by embedding micro pressure sensors and a radiofrequency antenna, forming a resonant circuit that enables wireless kidney pressure monitoring in an operating frequency of 40-50 MHz. The stent device is entirely packaged with Parylene-C for both biocompatibility and electrical insulation of the device in order to function in the real environment including urine, an electrically conductive liquid. A comparison between the results measured in in-vitro and ex-vivo settings show a good match in the sensitivity to applied pressure. In particular, the ex-vivo test in the kidney-ureter model pressurized with artificial urine in a cycled manner demonstrates wireless pressure tracking with a response of 1.3 kHz/mmHg, over pressures up to 37 mmHg that well covers a range of pressure increase known for chronic obstruction. This testing is enabled by the prototype placement into the ex-vivo model using the standard stenting technique and tools without noticeable functional degradation or failures, showing potential compatibility of the device with today's clinical need as a ureteral stent., Competing Interests: Declarations. Conflict of interest: The authors declare no conflict of interest. The authors declare no competing financial interests., (© 2024. The Author(s) under exclusive licence to Biomedical Engineering Society.)

Objective: To evaluate the available literature on ureteric stent-related infections, the use of antibiotics and bacterial colonisation to identify the current incidence of stent-related infections, unveil knowledge gaps and generate potential hypotheses for future research., Methods: A literature review was conducted using PubMed, Cochrane and urological association websites identifying relevant English literature published between 1983 and January 2024., Results: There is a worldwide lack of guidelines for antibiotic prophylaxis for stent placement, exchange or extraction. In patients with a negative preoperative urine culture undergoing ureteroscopy and stent placement, it may be considered to only provide prophylaxis in presence of risk factors. However, in pre-stented patients a preoperative urine culture is important to guide prophylaxis during endourological surgery. During stent indwell time, antibiotic prophylaxis does not show any advantage in preventing urinary tract infections (UTIs). There is no strong evidence to support the use of antibiotics at time of stent removal. In the absence of any clear evidence, management strategies for treating UTIs in patients with ureteric stents vary widely. Stent exchange could be considered to remove the biofilm as a potential source of bacteria. Stent culture can help to guide treatment during infection as urine culture and stent culture can differ., Conclusion: In terms of good antibiotic stewardship, urologists should be aware that unnecessary use of antibiotics provokes bacterial resistance. There is a great need for further research in the field of antibiotic prophylaxis and stent-related infections to develop evidence that can help shape clear guidelines for this very common urological practice., (© 2024 BJU International.)

Objective: To report on our first-in-human experience using the LithoVue Elite™ ureteroscope (Boston Scientific Corp., Marlborough, MA, USA) to measure intrarenal pressure (IRP) during flexible ureteroscopy., Patients and Methods: A single-arm retrospective observational analysis was performed in 50 consecutive patients undergoing ureteroscopic lithotripsy using the LithoVue Elite™ system with pressure sensing capability between April 2022 and February 2023 at two centres. A pressure bag set at 150 mmHg or hand irrigation with a 60-mL syringe was used for irrigation and a ureteric access sheath (UAS) was placed at the physician's discretion. Median and maximum IRPs, and relative cumulative time exceeding 20, 40, 60, 80, 100, 120, 140, 160, and 200 mmHg per total procedure time were analysed. The two-sample Mann-Whitney U-test was used, with statistical significance set at P < 0.05., Results: The median (interquartile range [IQR]) patient age and body mass index (BMI) was 62.5 (46.7-68.2) years and 27.6 (23.3-32.1) kg/m 2 , respectively. During the median (IQR) total procedure time of 31.9 (17.4-44.9) min, the median and maximum IRPs were 28.5 (20.0-47.5) and 174.0 (133.5-266.0) mmHg, respectively. IRP remained at <60 mmHg during 92% of the procedure times. Patients with Asian ethnicity, and those without pre-stenting or UAS use exhibited longer cumulative/total durations exceeding pre-defined IRP cut-off values. The smaller 10/12-F UAS did not lower pressures as much as the 11/13-F or 12/14-F UAS (P < 0.001). Age, diabetes, hypertension, preoperative α-blockade, stone size, and BMI did not show any statistically significant associations with IRP., Conclusions: The IRP can now be routinely measured during ureteroscopy. Patients had a median IRP of 28.5 mmHg and a maximum of 174 mmHg. Using a smaller UAS (10/12 F), Asian ethnicity, and tight ureters were found to have higher IRPs., (© 2023 The Authors. BJU International published by John Wiley & Sons Ltd on behalf of BJU International.)

Introduction: Intrarenal pressure is emerging as an important monitoring parameter during flexible ureteroscopy (fURS). We measure how intraoperative conditions affect intrarenal pressure using a novel pressure sensing ureteroscope. Methods: The LithoVue Elite (LVE) single-use digital flexible ureteroscope (Boston Scientific) is the first commercial ureteroscope that senses pressure at its tip. LVE was used in a porcine model to measure intrarenal pressure with and without a ureteral access sheath (UAS) with various sizes and placement locations, irrigation methods, and working channel accessories. LVE pressure accuracy was measured in a bench model. This abstract shows the least-square means from multiway analysis of variances used for analysis. Results: Intrarenal pressures were the highest without a UAS (64 mm Hg), followed by the 11/13 UAS (51 mm Hg) and the 12/14 and 13/15, which were not statistically different (39-40 mm Hg). The pressures were highest with UASs placed at the ureteropelvic junction (61 mm Hg), and lowest if placed in the renal pelvis (24 mm Hg). Irrigation methods showed the highest pressures with syringe (57 mm Hg), while irrigation bags (pressurized at 150-300 mm Hg) produced 43 to 46 mm Hg and 25 mm Hg when applied with 80 cm of gravity. Placing a 200 μm laser fiber reduced pressures from 44 to 41 mm Hg. Finally, the bench model showed that LVE was 96% accurate up to 300 mm Hg. Conclusion: Intrarenal pressure significantly varied based on UAS sizes, placement, and irrigation methods. Accordingly, fURS with LVE is poised to be an invaluable tool for clinical decision-making and future studies of intrarenal pressure.

Objective: The purpose of this study is to evaluate the current availability of technology for urolithiasis treatment and ureteroscopy (URS). Perioperative practice patterns, availability of ureteroscopic technologies, pre- and poststenting practices, and methods to alleviate stent-related symptoms (SRS) were assessed via a survey of members of the Endourological Society. Methods: We distributed a 43-question survey online via the Qualtrics platform to members of the Endourological Society. The survey consisted of questions pertaining to the following topics: general (6), equipment (17), preoperative URS (9), intraoperative URS (2), and postoperative URS (9). Results: A total of 191 urologists responded to the survey and 126 completed all questions of the survey (66%). Fifty-one percent (65/127) of urologists were fellowship trained and dedicated an average of 58% of their practice to stone management. In terms of procedures, most urologists performed URS most commonly (68%), followed by percutaneous nephrolithotomy (23%) and extracorporeal shockwave lithotripsy (11%). Ninety percent (120/133) of respondent urologists purchased a new ureteroscope within the last 5 years (16% single-use scopes, 53% reusable, and 31% purchased both). Fifty-three percent (70/132) of the respondents stated that they would be interested in a ureteroscope that can sense intrarenal pressure, with an additional 28% (37/132) stating they would be interested depending on the cost. Seventy-four percent (98/133) of responders purchased a new laser within the last 5 years, and 59% (57/97) changed their lasering technique due to the new laser. Urologists are performing primary ureteroscopy for obstructing stones in 70% of cases, and prefer prestenting patients for subsequent URS in 30% (on average after 21 days). Seventy-one percent (90/126) of responders insert a ureteral stent after uncomplicated URS, which is removed, on average, after 8 days in uncomplicated cases and 21 days after complicated URS. Most urologists give analgesics, alpha-blockers, and anticholinergics for SRS and <10% prescribe opioids. Conclusion: Our survey revealed urologists' eagerness for the early adoption of novel technologies and adherence to conservative practice patterns focused on patient safety.

Objectives: To investigate global changes in ureters at the transcriptional, translational and functional levels, both while stents are indwelling and after removal and recovery, and to study the effects of targeting pathways that play a potential role., Methods: Pig ureters were stented for varying amounts of time (48 h, 72 h, 14 days) and the impact on peristalsis, dilatation and hydronephrosis were assessed. RNAseq, proteomic, histological and smooth muscle (SM) function analyses were performed on ureteric and kidney tissues to assess changes induced by stenting and recovery. Pathway analysis was performed using Ingenuity Pathway Analysis software. To study the impact of possible interventions, the effects of erythropoeitin (EPO) and a Gli1 inhibitor were assessed., Results: Stenting triggers massive ureteric dilatation, aperistalsis and moderate hydronephrosis within 48 h. Pathways associated with obstruction, fibrosis and kidney injury were upregulated by stenting. Increased expression of GLI1, clusterin-α (a kidney injury marker) and collagen 4A2 (a fibrosis marker) was found in stented vs contralateral unstented ureters. EPO did not improve peristalsis or contraction force but did decrease non-purposeful spasming seen exclusively in stented ureters. Tamsulosin administration increased contractility but not rate of peristalsis in stented ureters., Conclusions: Ureters respond to stents similarly to how they respond to an obstruction, that is, with activation of pathways associated with hydronephrosis, fibrosis and kidney injury. This is driven by significant dilatation and associated ureteric SM dysfunction. EPO and tamsulosin induced mild favourable changes in SM physiology, suggesting that targeting specific pathways has potential to address stent-induced complications., (© 2022 BJU International.)

Purpose: To collect a multicentric database on behalf of TOWER research group to assess practice patterns and outcomes of retrograde intrarenal surgery (RIRS) for kidney stones., Methods: Inclusion criteria: age ≥ 18 years, normal renal/calyceal system anatomy, calculi of any size, number, and position., Study Period: January 2018 and August 2021. Stone-free status: absence of fragments > 2 mm, assessed post procedure according to the local protocol (KUB X-Ray and/or ultrasound or non-contrast CT scan)., Results: Twenty centers from fifteen countries enrolled 6669 patients. There were 4407 (66.2%) men. Mean age was 49.3 ± 15.59 years. Pain was the most frequent symptom indication for intervention (62.6%). 679 (10.2%) patients underwent RIRS for an incidental finding of stones. 2732 (41.0%) patients had multiple stones. Mean stone size was 10.04 ± 6.84 mm. A reusable flexible ureteroscope was used in 4803 (72.0%) procedures. A sheath-less RIRS was performed in 454 (6.8%) cases. Holmium:YAG laser was used in 4878 (73.1%) cases. A combination of dusting and fragmentation was the most common lithotripsy mode performed (64.3%). Mean operation time was 62.40 ± 17.76 min. 119 (1.8%) patients had an intraoperative injury of the ureter due to UAS insertion. Mean postoperative stay was 3.62 ± 3.47 days. At least one postoperative complication occurred in 535 (8.0%) patients. Sepsis requiring intensive care admission occurred in 84 (1.3%) patients. Residual fragments were detected in 1445 (21.7%) patients. Among the latter, 744 (51.5%) patients required a further intervention., Conclusion: Our database contributes real-world data to support to a better understanding of modern RIRS practice and outcomes., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objectives: To set out the second in a series of guidelines on the treatment of urolithiasis by the International Alliance of Urolithiasis that concerns retrograde intrarenal surgery (RIRS), with the aim of providing a clinical framework for urologists performing RIRS., Materials and Methods: After a comprehensive search of RIRS-related literature published between 1 January 1964 and 1 October 2021 from the PubMed database, systematic review and assessment were performed to inform a series of recommendations, which were graded using modified GRADE methodology. Additionally, quality of evidence was classified using a modification of the Oxford Centre for Evidence-Based Medicine Levels of Evidence system. Finally, related comments were provided., Results: A total of 36 recommendations were developed and graded that covered the following topics: indications and contraindications; preoperative imaging; preoperative ureteric stenting; preoperative medications; peri-operative antibiotics; management of antithrombotic therapy; anaesthesia; patient positioning; equipment; lithotripsy; exit strategy; and complications., Conclusion: The series of recommendations regarding RIRS, along with the related commentary and supporting documentation, offered here should help provide safe and effective performance of RIRS., (© 2022 The Authors. BJU International published by John Wiley & Sons Ltd on behalf of BJU International.)

Purpose: To evaluate the outcomes of pre-stented (PS) versus non-pre-stented (NPS) patients who have undergone retrograde intrarenal surgery (RIRS) for renal calculi with subgroup analysis of Asian and non-Asian cohorts., Methods: Protocol is registered in PROSPERO, CRD42021261123. Eligible studies identified from four electronic databases. Meta-analysis was done to enumerate the outcomes of RIRS in between PS and NPS. Secondary sub-analysis was done to look for differences in outcomes in Asian and non-Asian cohorts., Results: Fourteen studies involving 3831 patients (4 prospective, 10 retrospective studies) were included. PS patients experienced higher success rates of ureteral access sheath (UAS) insertion than NPS (RR 1.09, 95% CI 1.05-1.13, p < 0.00001). PS patients had lower risk of ureteral injuries from UAS placement (RR 0.69, 95% CI 0.50-0.96, p = 0.03). No significant differences in intra- and postoperative complications between two groups were found. Stone-free rate (SFR) outcomes for residual fragment (RF) cut-off of < 1 mm and < 4 mm favoured the PS patients (RR 1.10, 95% CI 1.04-1.17, p = 0.002 for < 4 mm, RR1.10, 95% CI 1.02-1.19, p = 0.02 for < 1 mm). In the subgroup analysis, PS Asian patients had similar SFR as NPS patients for SFR(< 4 mm) but non-Asian population showed better outcomes in the PS patients for SFR(< 4 mm) (RR 1.31, 95% CI 1.13-1.52, p = 0.0005)., Conclusions: This meta-analysis suggests that pre-stenting results in a higher success for UAS placement, minimising intraoperative ureteric injury, with higher overall SFR for any RF cut-off in PS cohorts. In non-Asian cohort, significant differences occurred at SFR < 4 mm but not for SFR < 1 mm. No difference was seen in our Asian cohort for any SFR cut-off in both PS and NPS patients., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: The holmium-YAG (Ho:YAG) Laser system is the current gold standard for laser lithotripsy (LL). Super Pulse Thulium Fiber Laser (SPTF) has emerged as an effective alternative. We compared the temperature profile of both the 120 W Ho:YAG and the 60 W SPTF systems during ureteral lithotripsy., Methods: Antegrade ureteroscopy with LL was performed in ex-vivo porcine kidneys with 3 mm Begostones. Intra-ureteral temperature was measured using one probe proximal and one distal to the site of lithotripsy. LL was performed using a 200 μm core fiber at dusting (SPTF-0.1 J, 200 Hz, SP; Ho:YAG-0.3 J, 70 Hz, LP) and fragmenting (0.8 J, 8 Hz, SP for both) settings for 5 s. Fifteen repetitions were recorded for each laser at each setting. Tissue samples of the ureter were collected for histological analysis., Results: There was a rise in temperature at the site of lithotripsy using both systems at every setting evaluated. The median temperatures were greater for the SPTF on the fragmenting setting (33.3 °C vs 30.0 °C, p = 0.004). On the dusting setting, the median temperature was not statistically greater for Ho:YAG (40.6 °C vs 35.8 °C, p = 0.064), (Graphic 1). Histological analysis did not show any signs of injury or necrosis in any of the tested settings., Conclusion: Higher power settings used for dusting have a higher temperature rise in the ureter during lasering. Median ureteral intra-luminal temperature rise during LL was equivalent during dusting and higher in the SPTF during fragmentation, but neither reached the threshold for thermal injury based on the duration of exposure., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.)

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.

INTRODUCTION To assess the relationship between pain after ureteral stent removal and patient and procedural factors., Materials and Methods: A validated survey designed to assess the relationship between quality of life and treatment decisions in kidney stone disease was randomly distributed to patients with a history of a ureteral stent in seven medical centers across North America participating in an endourology research collaborative between July 2016 and June 2018. The primary outcome was increased pain after ureteral stent removal. Statistical analyses were performed using Chi-square and multiple logistic regression., Results: A total of 327 surveys were analyzed. Twenty seven percent of patients reported increased pain in the hours after ureteral stent removal. Patients with a stent ≤ 7 days were significantly more likely to experience pain after stent removal compared to those with a stent > 7 days (33.3% versus 22.8%, p = 0.04). Female gender (OR: 2.41, 95% CI: 1.42-4.10) was associated with increased pain after stent removal, while increasing age was inversely associated (OR: 0.52, 95% CI: 0.36-0.74). After adjustment, patients with a stent > 7 days were significantly less likely to report pain in the hours after removal (OR: 0.59, 95% CI: 0.35-0.99)., Conclusions: Approximately one in four patients will experience increased pain after ureteral stent removal. Female patients, younger patients, and patients with a stent ≤ 7 days were more likely to experience an increase in pain immediately following stent removal. Understanding factors associated with post-stent removal pain may be helpful in counseling patients at high risk stent removal morbidity.

Ureteral stents are the most widely used surgical implant in urology. However, they may cause adverse effects to patients, including pain, discomfort, and inflammation. In this work, the inflammatory effect of stent placement and the associated elevation of cyclooxygenase-2 (COX-2) expression were observed. Furthermore, a capillary electrophoresis mass spectrometry (CE-MS) based approach was subsequently developed to quantify urinary prostaglandin E 2 (PGE 2 ), a COX-2 metabolite known to contribute to inflammatory renal diseases, to further interrogate the role of this pathway. Urine samples were cleaned and preconcentrated by solid-phase extraction (SPE), and an on-line sample stacking method was used for the enrichment of analytes. The accuracy, precision, and specificity of this method were validated. Standard addition methods were performed to assess the reliability of using deuterated internal standards (IS) in compensating the remaining matrix effect after SPE as well as the detector fluctuation. Through the analysis of 32 pig urine samples, a statistically significant increase of PGE 2 was observed in the stented group compared to the unstented (P = 0.01) and the recovered (P = 0.004) groups. This work determined that stent placement may contribute to COX-2-dependent inflammation and developed a reliable CE-MS based methodology to quantify PGE 2 in stented individuals that may further understand the biology of stent-associated inflammation and inform urologic patient management., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Purpose: Ureteral stents are fraught with complications. Not much is known regarding what causes these issues. Studies suggested that discoloration of indwelling stents changes surface characteristics to promote stent-associated complications. Occasional stent discoloration has been observed; however, underlying mechanisms and potential material changes are unknown. In this study, we identify a potential mechanism for stent discoloration and characterize potential changes in stent surface characteristics and their impact on encrustation and bacterial colonization. Materials and Methods: Twenty Polaris Ultra and 20 Percuflex Plus stents (same polymer material) with varying degrees of discoloration were collected from Japanese and Canadian patients. Surface characterization using scanning electron microscopy and Fourier transmission infrared spectroscopy was conducted. Encrustation of variably discolored stents was assessed via atomic absorption spectroscopy and bacterial adhesion to discolored and control stents via colony-forming unit counts. Results: Bismuth subcarbonate was found in control stents, and discoloration was induced via incubation in 1% sodium sulfide and increasing concentrations of hydrochloric acid (HCl) to produce hydrogen sulfide (H 2 S). Discoloration of either patient-derived stents or in vitro discolored stents did not result in significant changes in stent material or increased rates of encrustation or bacterial adhesion. Conclusions: Ureteral stent discoloration may be triggered by sulfur containing urinary components reacting with bismuth subcarbonate in the stent material, rather than the surface deposition of unusual crystals as previously proposed. Stent discoloration does not result in increased levels of encrustation or bacterial adhesion. Given this, stent discoloration appears to be cosmetic and has no effect on the functionality of the indwelling stent.

Purpose of Review: Ureteral stents are necessary in the routine practice of an urologist. Choosing the correct stent and being aware of the options available will allow urologists to provide the best possible care for patients and value to the healthcare system. This review seeks to educate urologists regarding improvements in stent technology currently available or in development., Recent Findings: Research from around the world is underway to discover an ideal stent - one that is comfortable for patients, resists infection and encrustation and is affordable for hospital systems. Stent design alterations and stent coatings are revealing reductions in encrustation and bacterial colonization. Biodegradable stents and magnetic stents are being tested to prevent the discomfort of cystoscopic removal. Intraureteral stents are proving efficacious while eliminating an irritating coil from the bladder and the symptoms associated with it., Summary: The studies highlighted in this review provide encouraging results in the pursuit of the ideal stent while opening discussion around new concepts and further areas of research.

Ureteral stents are an indispensable tool in contemporary urologic patient care. They have become first-line devices for maintenance of ureteral patency postoperatively and in cases of ureteral narrowing. Despite their widespread use, these implants are associated with multiple complications including stent colic, infection, and encrustation. There is no ideal ureteric stent currently available. The aim of most recent stent innovation has been to make steps toward properties of an ideal stent. This article reviews recent technological advances in stent design and how they have attempted to tackle issues that urologists and patients face with ureteral stents., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Objective: To better understand the effects of double J stenting on ureteral physiology and function., Materials and Methods: In total, 24 pigs were stented cystoscopically unilaterally for 48 hours, 1, 2, 4, and 7 weeks. Controls consisted of un-stented animals (n = 4) or the contralateral un-stented ureter in pigs. Ureters were harvested and tested in tissue baths to evaluate their contractility. Ureteral inflammation and expression of Sonic Hedgehog (Shh) and the transcriptional activator Gli1 (the downstream target of active Hedgehog signaling) were assessed histologically and by immunohistochemistry, respectively., Results: Indwelling ureteral stents were found to abolish normal ureteral function in all animals. Specifically, ureteral smooth muscle (SM) activity was significantly diminished within 48 hours after stenting and persisted at the 1-week time point. Furthermore, ureteral SM dysfunction was associated with increasing ureteral dilation due to the indwelling stent. Simultaneously, we observed a loss of Gli1 expression in SM cells, with a concomitant increase in ureteral inflammation. Expression of Shh was restricted to the urothelium and was not different between controls, stented, and contralateral ureters., Conclusion: Stent-induced aperistalsis was associated with diminished SM contractility, increased tissue inflammation, and reduced Gli1 expression in ureteral SM cells, independent of Shh expression. The present study is the first to show that indwelling stents negatively affect ureteral SM activity and identify a role for specific molecular mechanisms involved., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Purpose of Review: Ureteral stents are commonly used in urology, but there is no perfect ureteral stent. This review documents developing ureteral technologies and strategies over the past 2 years. This area has some progressive advances in the foreseeable future., Recent Findings: Publications from 2014 and 2015 from a PubMed search with the words 'ureter' and 'stent' in the title were reviewed. Topics that affected patient symptoms from stents include selecting the proper length of stent, patient education regarding stent symptoms, and how the stent is removed. Stent extraction strings have been studied and not increased the incidence of infection or pain. There have been several publications examining antirefluxing ureteral stents that reduced vesicoureteral reflux during micturition and infection of transplanted kidneys. Other novel methods of removing a stent include new biodegradable ureteral stents and metal beads attached to the stent used in tandem with a magnetic catheter. Several new metal and mesh stents were described for use in patients with malignant ureteral obstruction. Last, new stent coatings with antimicrobial peptides have also been described., Summary: The search continues for the perfect stent and there has been promising progress over the past 2 years.

Purpose of Review: We review new therapies and biomaterials designed to reduce ureteral stent symptoms in patients undergoing ureteroscopy., Recent Findings: Pharmacologically, alpha blockers and antimuscarinics have been shown to have a synergistic effect and be more effective than either medication alone in reducing stent-related symptoms. Prestenting patients prior to ureterosocpy has been shown to be beneficial for patients with renal stones, offering a better stone-free rate and reduced complications, but not for ureteral stones. Stenting after use of a ureteral access sheath reduced complications and unscheduled emergency visits. Nonsteroidal anti-inflammatories have been shown to prevent pain after stent removal. Surveys showed that patients preferred to remove their own stents via dangle strings at home or undergo cystoscopic removal in the operating room with some type of anesthesia. New materials such as gel-based or biodegradable ureteral stents are being developed to deal with stent-related pain, encrustation, and infection. Antirefluxing stents eliminate vesicoureteric reflux in patients during voiding and may reduce symptoms of back and flank pain. Ureteral stents are involved in many procedures in urology and particularly kidney stone treatments., Summary: Advances in materials and medications will help improve the patient experience for those who receive a ureteral stent.

Ureteral stents are one of the most commonly used devices in the treatment of benign and malignant urological diseases. However, they are associated with common complications including encrustation, infection, pain and discomfort caused by ureteral tissue irritation and possibly irregular peristalsis. In addition, stent migration and failure due to external compression by malignancies or restenosis occur, albeit less frequently. As these complications restrict optimal stent function, including maintenance of adequate urine drainage and alleviation of hydronephrosis, novel stent materials and designs are required. In recent years, progress has been made in the development of drug-eluting expandable metal stents and biodegradable stents. New engineering technologies are being investigated to provide stents with increased biocompatibility, decreased susceptibility to encrustation and improved drug-elution characteristics. These novel stent characteristics might help eliminate some of the common complications associated with ureteral stenting and will be an important step towards understanding the behaviour of stents within the urinary tract.

Purpose: Ureteral stents are prone to irritation, encrustation and infection, and they require additional procedures for removal. Furthermore, indwelling polymer stents are often forgotten with devastating consequences to the patient. We describe the degradation time, and physiological and histological responses elicited by a novel biodegradable ureteral stent in a porcine model., Materials and Methods: A total of 16 female Yorkshire pigs were used in the study. Ten biodegradable Uriprene™ stents and 6 biostable Polaris™ stents were cystoscopically inserted unilaterally in 2 groups of animals. Excretory urogram, and blood and urine tests were performed on different days until day 28. Biostable stents were removed on day 21. On day 28 all pigs underwent necropsy for microscopic and histological evaluation., Results: Nine of the 10 biodegradable stents (90%) degraded completely by 4 weeks, while 1 pig had 3 fragments smaller than 1.5 cm in the bladder. Excretory urogram showed equivalent drainage and significantly less hydronephrosis in biodegradable stented kidneys. Blood and urine parameters were similar in the 2 groups. A transient increase in serum creatinine on day 7 in 40% of the pigs with a degradable stent resolved by day 10. There were significantly fewer abnormal histological findings in the degradable stent group. We evaluated drainage characteristics in an unobstructed ureter and results may not be representative of what develops in obstructed ureters., Conclusions: The third generation biodegradable stent is a safe, effective alternative to conventional polymer stents, resulting in equivalent drainage and less hydronephrosis., (Copyright © 2013 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.)

Background and Purpose: Ureteral stents often cause significant patient morbidity that can be difficult to treat. Drug-eluting stent technology allows the local delivery of a drug. Our previous work demonstrated that ketorolac instilled intravesically at the time of ureteral stent insertion significantly decreased flank pain compared with controls. We sought to determine the safety of a novel ketorolac-eluting ureteral stent., Materials and Methods: A total of 92 Yorkshire pigs were randomized to 1 of 5 groups. The oral control group consisted of 12 animals with transurethrally inserted control ureteral stents and 5 days of oral ketorolac. Twenty animals in each of the remaining groups received a control stent, or 15%, 13%, or 7% ketorolac-loaded stents. Ketorolac levels were measured in plasma, urine, and tissue sampled from ureters, bladder, kidneys, and liver using high performance liquid chromatography. Necropsies were performed to evaluate tissue pathology., Results: The majority of ketorolac was released within the first 30 days. The highest levels of ketorolac in plasma, kidney, and liver occurred in the oral control group. The highest levels of ketorolac found in ureteral and bladder tissues occurred in the ketorolac-stent groups in a dose-dependent fashion. No adverse events were noted in any of the ketorolac-stent groups. Gastric ulcerations were identified only in the oral control group. No abnormalities were identified in any other internal organs in any group., Conclusions: The use of ketorolac-eluting ureteral stents has proven to be safe in a porcine model. The ketorolac-stent group had less than 12% of the ketorolac concentration in plasma, kidney, and liver tissues compared with the oral ketorolac group. Ureteral tissues displayed the highest levels of ketorolac. Clinical studies are needed to determine if ketorolac-elution reduces stent symptoms.

Purpose: Ureteral stents are commonly used to facilitate kidney drainage but they may produce significant stent symptoms and morbidity, and require a secondary procedure for removal. Previous biodegradable stents showed bio-incompatibility or inconsistent degradation, requiring extra procedures to remove undegraded stent fragments. We previously reported a first generation biodegradable stent composed of suture-like material that required placement through the lumen of a sheath and degraded by 10 weeks. We now report second and third generation biodegradable stents that degrade more rapidly and can be placed directly over a polytetrafluoroethylene guidewire., Materials and Methods: Two groups of 16 Yucatan pigs each were unilaterally stented endoscopically with a control nondegradable (biostable) stent or a second generation degradable Uriprene stent. Blood studies, renal ultrasound and excretory urography were done throughout the study to determine renal function, hydronephrosis and stent degradation. Genitourinary organs were harvested at necropsy for pathological analysis. A third generation stent designed to improve degradation time was bilaterally implanted endoscopically into 4 Yorkshire Farm pigs (total of 8 stents), followed by excretory urography weekly to assess degradation and kidney function. Biomaterial parameters were tested., Results: Second generation stents began degrading at 2 weeks and were completely degraded by 10 weeks. All third generation stents were degraded by 4 weeks. Hydronephrosis was considerably less in the Uriprene group than in control biostable stented kidneys. Biostable stented ureters showed an average higher degree of inflammation, uropathy and nephropathy. Physical characteristics indicate that Uriprene stents are significantly more resistant to stent compression and have markedly higher tensile strength and coil strength comparable to that of other commercially available plastic stents., Conclusions: Our study confirms that Uriprene stents are biocompatible and provide good renal drainage. They hold promise for decreasing the need for a secondary procedure and stent related morbidity, such as infection and irritative symptoms., (Copyright 2010 American Urological Association. Published by Elsevier Inc. All rights reserved.)

Background and Purpose: Long-term use of ureteral stents is prevented by biofilm-related infection and encrustation mandating stent changes every few months. Triclosan is a broad-spectrum antimicrobial in numerous consumer and medical products and has been incorporated into a ureteral stent. We sought to determine the clinical effects of the triclosan-eluting stent in patients who needed long-term ureteral stenting., Patients and Methods: Eight patients with long-term stents were enrolled prospectively. All received a control stent for 3 months along with preoperative and postoperative antibiotics. After 3 months, the control stent was removed, and a triclosan-eluting stent was placed for 3 months with no antibiotics administered. For both indwelling periods, urine cultures were obtained weekly and biweekly for the first and last 6 weeks, respectively, and antibiotics were prescribed when patients had both a positive urine culture and symptoms of urinary tract infection. On removal, stents were assessed for microorganisms and encrustation., Results: Overall, similar microorganisms were isolated during each indwell period, although Staphylococcus and Enterococcus strains were isolated more frequently during control and triclosan stenting, respectively. Significantly fewer antibiotics were used during triclosan stenting, coinciding with a slightly higher number of positive urine cultures and significantly fewer symptomatic infections. No bacterial isolates developed antibiotic resistance during triclosan stent placement., Conclusions: Antibiotic use with control stents resulted in bacterial antibiotic resistance, which was not the case with the triclosan-eluting stents. Although triclosan-eluting stents did not show a clinical benefit in terms of urine and stent cultures or overall subject symptoms compared with controls, their use did result in decreased antibiotic usage and significantly fewer symptomatic infections. The triclosan-eluting stent alone is not sufficient to reduce device-associated infections in this difficult patient population.

Background and Purpose: Ureteral stents may cause significant morbidity, including pain, dysuria, hematuria, and infection. New biomaterials, coatings, and designs have been studied in an attempt to reduce stent-related symptoms, but to date, the ideal comfortable stent has not been developed. In order to facilitate development of a stent that will mold and change with patient movement, we examined stent and ureteral movement with changes in patient body position., Patients and Methods: Four women and two men with a median age of 60.5 +/- 7.7 years who underwent shockwave lithotripsy and insertion of a ureteral stent were enrolled. Static radiographs were performed with the patients in four positions: supine, standing, sitting, and bending forward. Differences in stent position were analyzed digitally relative to fixed bony reference points to determine ureteral movement., Results: The renal stent curl was most cephalad when the patient was supine and moved caudally an average of 2.5 +/- 1.5 cm when the patient stood up. The absolute vertical length of the stent was greatest when the patient was supine (31.1 +/- 1.2 cm) and shortened with standing (28.3 +/- 2.3 cm) and sitting (26.6 +/- 1.5 cm). The bladder curl moved an average of 2.3 +/- 1.2 cm vertically with patient movement., Conclusions: By measuring stent position, we were able to quantify the range of motion of the ureter during changes in body position. Stent movement appears to be a combination of bowing in the proximal ureter and moving within the bladder. Future stent designs may take this into account to decrease stent-related symptoms.

Background and Purpose: The gold standard treatment for upper-tract transitional-cell carcinoma is radical nephroureterectomy, but management of the distal ureter is not standardized. Two treatment options to detach the distal ureter are open cystotomy (OC) and excision of a bladder cuff or transurethral incision of the ureteral orifice (TUIUO). We compared the clinico-pathologic outcomes of these two techniques., Patients and Methods: Hospital records were reviewed on all 51 patients who had undergone open or laparoscopic nephroureterectomy at our institution between 1 January 1990 and 30 June 2005. Patient demographics, intraoperative parameters, and pathology data were collected. The mean follow-up was 23.2 months (range 4.5-75 months) and 22.1 months (range 1-50 months) for the OC and TUIUO groups, respectively. There were no significant differences in sex, age at operation, American Society Anesthesiologists risk score, previous transitional-cell tumors, pathologic tumor grade and stage, or metastatic disease status in the two groups., Results: Five patients had an unplanned incomplete ureterectomy. The bladder recurrence rates were similar in the OC group (22.2%; 6/27) and the TUIUO group (26.3%; 5/19). There were no pelvic recurrences in either group. Four of the five patients who had an incomplete ureterectomy had tumor recurrences, three in the form of metastatic disease., Conclusion: Management of the distal ureter by TUIUO in appropriate patients offers the same rate of bladder recurrence as OC. Incomplete ureterectomy results in a significantly higher rate of recurrence, often associated with the development of metastatic disease.

Purpose: Infection and encrustation remain major limitations of ureteral stent use and to our knowledge no device has completely overcome these obstacles to date. Triclosan is a biocide currently used in a plethora of consumer and medical products that has recently been loaded into a ureteral stent. Using a rabbit model of UTI we examined the effects of triclosan impregnated stent segments on the growth and survival of Proteus mirabilis, a uropathogen commonly associated with device related UTI and encrustation., Materials and Methods: A total of 48 male New Zealand White rabbits were instilled transurethrally with 1 x 10(6) P. mirabilis 296. A stent curl from a triclosan eluting, Percuflex Plus or Optima ureteral stent was placed intravesically. Urine was cultured on days 1, 3 and 7. On day 7 the stents were assessed for encrustation and viable organisms, while the bladders were scored for the degree of inflammation., Results: Throughout the study urine isolated from the triclosan group contained significantly fewer viable organisms than controls with 7 of 13 animals completely clearing the infection by day 7. Similarly 9 of 13 triclosan eluting stents showed no viable organisms upon recovery and the remaining 4 showed significantly fewer organisms than controls. Urine and stents in all controls were positive for P. mirabilis at all time points. Although there was no significant difference in encrustation among the groups, bladders harvested from the triclosan group demonstrated significantly less inflammation., Conclusions: Triclosan eluting stents greatly decreased P. mirabilis growth and survival in a rabbit UTI model compared to controls. These stents may prove useful for decreasing device related P. mirabilis UTIs.

Ureteral stents are an important tool for aiding upper urinary tract drainage, but can cause significant patient morbidity. Common problems include stent-induced pain, hematuria, dysuria, infection, and encrustation. From a urologist's perspective, stents must be easy to maneuver in the urinary tract, radiopaque, and affordable. Since the development of the modern day stent in 1978, stents have evolved to include softer biomaterials that are more resistant to encrustation and infection. An ideal biomaterial is one that is not affected by its environment and does not elicit reactive changes in surrounding tissues. To date, the ideal biomaterial or stent does not exist. This review discusses developments that address the issues of infection, biofilm formation, encrustation, and patient comfort. Stent materials including polyurethane, silicone, biodegradable substances and new combination polymers are reviewed, in addition to novel stent coatings such as heparin, hydrogel, and silver nitrate. Ureteral stent technologies currently lag behind vascular stents, particularly drug-eluting stents, but new developments will continue to improve these essential urological tools.