A systematic review of long-duration stents for ureteral stricture: which one to choose?

Recent developments in ureteral stent: Substrate material, coating polymer and technology, therapeutic function

The ureteral stent is an effective treatment for clinical ureteral stricture following urological surgery, and the functional coating of the stent could effectively inhibit bacterial colonization and other complications. The present review provides an analysis and description of the materials used in ureteral stents and their coatings. Emphasis is placed on the technological advancements of functional coatings, taking into consideration the characteristics of these materials and the properties of their active substances. Furthermore, recent advances in enhancing the therapeutic efficacy of functional coatings are also reviewed. It is anticipated that this article will serve as a valuable reference providing insights for future research development on new drug-loaded ureteral stents.

Risk factors for migration of retrievable covered expandable metallic stent in patients with persistent benign ureter strictures

PURPOSE

The purpose of this study is to evaluate the incidence, risk factors, and salvage management of retrievable covered expandable metallic stent (RCEMS) migration in patients with persistent benign ureter strictures.

MATERIALS AND METHODS

A retrospective study was performed on 117 consecutive patients who underwent implantation of RCEMS. Univariate and multivariate analyses were used to identify prognostic factors for stent migration, including stricture location and length, hydronephrosis-cortex ratio, ureteral dilation, and the diameter of the narrowest portion of the stricture.

RESULTS

Stent migration occurred in 22 (19.5%) of 113 patients who met inclusion criteria. Of the 22 patients, 16 (72.7%) had ordinary ureteral stricture, 3 (13.6%) had stricture in transplanted kidneys, and 3 patients (13.6%) had ureter stricture in orthotopic neobladders. The mean creatinine for the entire cohorts showed significant improvement (p = 0.038). Multivariate analysis identified the following prognostic factors for migration: distal ureteral stricture (p = 0.006), patients who underwent balloon dilation (p = 0.003), hydronephrosis-cortex ratio ≧10 (p = 0.017), larger diameter of wasting of RCEMS (p < 0.001), and patients with a shorter stricture length (p = 0.006). Salvage management was required in 4 of the 22 patients. The strictures in the remaining 18 patients improved with observation.

CONCLUSIONS

Stent migration is more likely to occur in patients with the five prognostic factors mentioned above. Our study developed a nomogram to predict stent migration in patients with ureteral strictures treated using RCEMS.

Metal ureteral stents for ureteral stricture: 2 years of experience with 246 cases

BACKGROUND

Metal ureteral stents (MUS) has gained popularity as an endoscopic treatment alternative for the management of ureteral strictures. The aim of this study was to evaluate the safety, efficacy, and tolerability of MUS for treating ureteral strictures and to identify any factors that could influence the success of this intervention.

METHODS

This study is a prospective analysis of the efficacy and safety of MUS for treating ureteral strictures in a single-center setting. The study enrolled 246 patients who had been diagnosed with ureteral strictures and had undergone MUS placement between January 2019 and July 2021. The patients were followed-up for a duration of 2 years.

RESULTS

The overall success rate of MUS placement was 71.7%. Furthermore, the success rate of ureteral strictures after kidney transplantation (78.2%) was significantly higher than common ureteral strictures (73.0%) or recurrent ureteral strictures (67.6%). Additionally, postsurgery, there was a considerable reduction in hydronephrosis volume (68.9±96.1 vs. 32.1±48.8 cm 3 ), blood creatinine level (103.7±49.8 vs. 94.4±47.5 mol/l) and urea nitrogen level (6.7±7.2 vs. 5.1±2.4 mmol/l). The study also reported that the rate of adverse events associated with MUS was relatively low, included hematuria (7.9%), pain (6.8%), urinary tract infection (6.4%), and lower urinary tract symptoms (5.3%).

CONCLUSIONS

MUS appear to be a safe and effective treatment option for ureteral strictures, with a high success rate and low complication rate. These results have important implications for the management of ureteral strictures and can help guide clinical decision-making in the selection of treatment options.

Allium® ureteral stent, a new player in the treatment of ureteral stenosis: a prospective cohort study

INTRODUCTION AND OBJECTIVES

Ureteral stricture is a chronic condition that can result in the obstruction of urinary drainage from the affected renal unit, leading to loss of renal function. Treatment methods can be categorized into two main headings: endourological and reconstructive procedures. We aimed to investigate the efficacy and safety of the self-expandable Allium® ureteral stent, which has been used in the minimally invasive treatment of ureteral stenosis in recent years.

MATERIALS AND METHODS

Twenty patients who were applied Allium® ureteral stent between 2017 and 2021 included in the study. The demographic and clinical characteristics of the patients, the details of the treatments applied to the patients, the perioperative and postoperative complications, the treatments applied for the complications and the findings in the follow-up were recorded and evaluated prospectively.

RESULTS

Etiology included urolithiasis in 16 patients (80%), malignancy in 3 patients (15%), and a previous gynecological operation in 1 patient (5%). Stent obstruction was found to be the most common complication in 3 patients (15%). Stent migration was the second most common complication in 2 patients (10%). Our follow-up continues with 15 patients without stent-related complications and stent obstruction. The mean follow-up period was 28 ± 15.7 months.

CONCLUSIONS

Allium ureteral stent is an effective and reliable method in the minimally invasive treatment of ureteral stricture with complications seen at acceptable rates and ease of treatment in the management of complications.

Evaluation of Renal Function and Stent Durability Following Resonance Stent Placement for Benign Disease

Introduction: The metal-based Resonance stent (RS) has traditionally been placed in patients with malignant ureteral obstruction; as such, the long-term utility of RS among patients with benign ureteral obstruction (BUO) remains underinvestigated. Methods: We retrospectively reviewed our database for patients with BUO who underwent RS placement between 2010 and 2020. The impact of chronic RS placement on renal function was evaluated by estimated serum creatinine-based glomerular filtration rate (eGFR), furosemide renal scan, and CT-based renal parenchymal volume measurement. The number of and reason for RS stent exchanges during the follow-up period, incidence of encrustation, and the average indwell time were recorded. A cost analysis of placing the RS vs a polymeric stent was performed. Results: Among 43 RS patients with BUO, at a mean follow-up of 26 months, there was no change in eGFR (p = 0.99), parenchymal volume (p = 0.44), or split renal function of the stent-bearing side on renal scan (p = 0.48). The mean RS indwell time was 9.7 months. Eleven patients (26%) underwent premature stent replacement (6 cases) or removal (5 cases). Stents in 9 patients (32%) were encrusted, of which 4 (44%) required laser lithotripsy. Overall, 25 patients (58%) and 12 patients (28%) had a mean stent indwell time of ≥6 months and ≥12 months, respectively. Placing an RS resulted in a 52%, 37%, and 5.6% cost reduction compared with a regular polymeric stent placement, where it was exchanged every 6, 4, or 3 months, respectively. Conclusions: RS deployment in the patient with a BUO results in cost-effective maintenance of renal function and of renal parenchymal volume at a mean follow-up of 2 years; however, only 28% of patients fulfilled the 1-year criterion for RS indwell time.

Unveiling the Challenges in Tandem Ureteral Stent Management for Malignant Ureteral Obstruction: Failure Rate, Risk Factors, and Durability of Their Replacement

BACKGROUND

Malignant ureteral obstruction (MUO) is a sequela of advanced malignant disease that requires renal drainage, with tandem ureteral stents (TUSs) being a viable option. This study aimed to evaluate the TUS failure rate, associated risk factors, and the feasibility of replacing failed TUSs with a new pair of stents.

METHODS

A retrospective analysis of MUO patients treated with TUS insertion from 2014 to 2022 was conducted. TUS failure was defined as urosepsis, recurrent urinary tract infections, acute kidney failure, or new hydronephrosis on imaging. Cox proportional hazard regression analysis identified the independent predictors of TUS failure.

RESULTS

A total of 240 procedures were performed on 186 patients, with TUS drainage failing in 67 patients (36%). The median time to failure was 7 months. Multivariate analysis revealed female gender (OR = 3.46, p = 0.002), pelvic mass (OR = 1.75, p = 0.001), and distal ureteral obstruction (OR = 2.27, p = 0.04) as significant risk factors for TUS failure. Of the failure group, 42 patients (22.6%) underwent TUS replacement for a new pair. Yet, 24 (57.2%) experienced a second failure, with a median time of 4.5 months. The risk factors for TUS second failure included a stricture longer than 30 mm (OR = 11.8, p = 0.04), replacement with TUSs of the same diameter (OR = 43, p = 0.003), and initial TUS failure within 6 months (OR = 19.2, p = 0.006).

CONCLUSIONS

TUS insertion for the treatment of MUO is feasible and has good outcomes with a relatively low failure rate. Primary pelvic mass and distal ureteral obstruction pose higher risks for TUS failure. Replacing failed TUSs with a new pair has a success rate of 42.8%. Consideration should be given to placing larger diameter stents when replacing failed TUS.

Effect of ureteral stent length and implantation position on migration after implantation

BACKGROUND

Ureteral obstruction is a urinary system disease that causes urinary retention, renal injury, renal colic, and infection. Ureteral stents are often used for conservative treatment in clinics, and their migration usually results in ureteral stent failure. The migrations include proximal migration to the kidney side and distal migration to the bladder side, but the biomechanism of stent migration is still unknown.

METHOD

Finite element models of stents with lengths from 6-30 cm were developed. The stents were implanted into the middle of the ureter to analyze the effect of stent length on its migration, and the effect of stent implantation position on 6-cm-long stent migration was also observed. The stents' maximum axial displacement was used to assess the ease of stent migration. A time-varying pressure was applied to the ureter outer wall to simulate peristalsis. The stent and ureter adopted friction contact conditions. The two ends of the ureter were fixed. The radial displacement of the ureter was used to evaluate the effect of the stent on peristalsis.

RESULTS AND DISCUSSION

The maximum migration occurs in the positive direction for a 6-cm-long stent implanted at the proximal ureter (CD and DE), but in the negative direction at the distal ureter (FG and GH). The 6-cm-long stent demonstrated almost no effect on ureteral peristalsis. The 12-cm-long stent diminished the radial displacement of the ureter from 3-5 s. The 18-cm stent diminished the radial displacement of the ureter from 0-8 s, and the radial displacement within 2-6 s was weaker than other time. The 24-cm stent diminished the radial displacement of the ureter from 0-8 s, and the radial displacement within 1-7 s was weaker than other time.

CONCLUSION

The biomechanism of stent migration and ureteral peristalsis weakening after stent implantation was explored. Shorter stents were more likely to migrate. The implantation position had less influence on ureteral peristalsis compared with the stent length, which provided a reference for stent design aimed at reducing stent migration. Stent length was the main factor affecting ureteral peristalsis. This study provides a reference for the study of ureteral peristalsis.

3-Carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) induces cell death through ferroptosis and acts as a trigger of apoptosis in kidney cells

Ferroptosis is a cell death mechanism characterized by intracellular iron accumulation and lipid peroxidation. Effects of uremic toxins on ferroptosis in the kidney are not well understood. We investigated whether protein-bound uremic toxins induce ferroptosis, resulting in cell death, using the bilateral ureteral obstruction (BUO) mouse model and kidney cells. In BUO mice, we observed elevated lipid peroxidation, increased iron concentration, and decreased glutathione peroxidase 4 (GPX4) expression. Levels of transferrin receptor 1 and system Xc-, which are involved in iron transport and storage, were also elevated, while those of ferritin heavy and light chains (FHC and FLC) were reduced. Treatment of HK-2 and NRK49F kidney cells with CMPF decreased GSH levels and the expression of GPX4, FHC, and FLC, and increased levels of ROS, lipid peroxidation, and intracellular iron concentration. CMPF-induced and erastin-induced decreases in GPX4 levels and increases in Bax and cytochrome C levels were counteracted by ferrostatin-1 pretreatment. However, GPX4 mRNA levels, protein abundance, or promoter activity were not restored by Z-VAD-FMK, a multi-caspase inhibitor. These results suggest that ferroptosis induced by CMPF treatment induces apoptosis, and inhibition of ferroptosis reduces apoptosis, suggesting that ferroptosis plays a role in triggering cell death by apoptosis.

[Long-term efficacy evaluation of coated metal stent implantation for ureteroscopic lithotripsy related refractory ureteral stricture]

OBJECTIVE

To comprehensively evaluate the long-term efficacy and safety of coated metal stent implantation for ureteroscopic lithotripsy related refractory ureteral stricture (URL-rUS).

METHODS

Electronic medical records of 30 patients (31 affected renal units) receiving coated metal stent implantation for URL-rUS from Sept. 2018 to Aug. 2021 at Peking University People' s Hospital were reviewed for analysis. Coated metal stents were implanted in retrograde approach via ureteroscope. Last outpatient follow-up was set as endpoint. Baseline information, stricture characteristics and decompression strategy before coated metal stent implantation were retrospectively collected. Serum creatinine (Scr) concentration and renal pelvis width (RPW) were used as renal function indicators. Peri-operative and long-term complications and according outcomes were recorded. For the patients who had double J tubes implanted for drainage before operation, Ureteral Stent Symptom Questionnaire (USSQ) was applied to evaluate the stent-related discomforts and quality of life (QoL) before and after surgery. Data analysis was conducted with SPSS (version 25.0; SPSS, Chicago, IL, USA).

RESULTS

Totally 30 patients with 31 affected renal units were included. All the patients previously underwent unsuccessful traditional endoscopic balloon dilation or endoureterotomy before receiving coated metal stent implantation. The mean age was (45.5±9.3) years old. The median follow-up time were 14 (6-36) months. All coated metal stents were successfully placed with a median duration of 60 (30-195) min. No severe peri-operative complications occurred. At endpoint, 28 (90.3%) sides of coated metal stents remained unobstructed with a longest indwelling time of 36 months. Causes of failures included stent migration (1 case, 3.2%), encrustation (1 case, 3.2%) and repeated stent related urinary tract infection (1 case, 3.2%). When compared with the baseline, significant reductions were observed in both Scr concentration and RPW at endpoint [(90.7±19.5) mmol/L vs. (83.1±18.5) μmol/L, P < 0.01, for Scr; (2.5±1.3) cm vs. (1.9±0.8) cm, P < 0.01, for RPW], indicating good preservation of renal function and remission of hydronephrosis. For 26 patients with double J stents before operation, significant reduction of USSQ average score (100.4±6.6 vs. 82.1±4.9, P < 0.01) evidenced better life quality preserving ability of coated metal stent versus double J stent.

CONCLUSION

Coated metal stent implantation is a safe and minimally invasive management of ureteral stricture providing a satisfying long-term patency rate, after which the patients' quality of life and renal function could be both improved. This method could serve as a promising alternative long-term maintenance treatment option for patients with URL-US, especially when traditional endoscopic interventions failed.

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.

Comparison of Ureteral Stents on Drainage Performance Under Extrinsic Compression

PURPOSE

By investigating deformation and flow velocity of three commonly used, readily accessible ureteral stents under variant compression and surface change at three time points (new, 1 month or 3 months after implantation), we share our center's experience dealing with ureteral obstruction especially the malignant ones.

MATERIALS AND METHODS

Ureteral double-J (DJ) stents including Cook Universa Soft, Kang Yi Bo (KYB) antireflux and Urovision Visiostar ESWL DJ stents went though scanning microscopic (SEM) analysis. Compression-deformation was measured using digital force gauge. Intraluminal flow velocity was tested with the stents under different compression levels.

RESULT

Urovision Visiostar demonstrated significantly better anti-compression capability. Cook Universa Soft and KYB antireflux showed favorable draining velocity without compression, but the velocity dropped heavily under compression; the velocity of KYB antireflux reduced heavily after 3 months of implantation; Urovision Visiostar achieved the best draining effect under compression at all three time points.

CONCLUSION

The Urovision Visiostar DJ stent demonstrated significantly greater resistance to compression than the other two, and better drainage under compression. Patients with benign or malignant ureteral compression might benefit from using the Urovision Visiostar stents. Large prospective clinical trials are needed for confirmation.

Tumor stent for chronic ureteral obstruction: Which are predictors of stent failure?

PURPOSE

To identify predictors of UROSOFT® tumor stent failure. According to the manufacturer, this reinforced ureteral stent has a maximal dwell time of 6 months. Nonetheless, stent failure may reduce this maximal dwell time.

METHODS

All patients undergoing first-time UROSOFT® tumor stent insertion in our institution between 2010 and 2018 were considered for this retrospective analysis. Primary endpoint was stent failure and defined as premature stent exchange or percutaneous nephrostomy insertion.

RESULTS

182 patients were available for analysis. Median age was 68 years. Causes for tumor stent placement were extrinsic ureteral obstruction in 144 patients (79 %) and intrinsic obstruction in 38 patients (21 %). Tumor stent failure free survival estimates at 1, 2, 3, 4 and 5 months were 89%, 83%, 76%, 65% and 52%, respectively. Patients with stent failure had significantly higher grade of hydronephrosis, higher urinary culture bacterial growth, higher serum WBC, higher CRP and lower eGFR at the time of re-intervention, compared to patients who underwent regular stent exchange. Of all baseline and perioperative parameters, we found bilateral insertion, intrinsic ureteral obstruction, and urinary tract infection (UTI) at time of tumor stent insertion to be significant and independent predictors of stent failure (all p < 0.05).

CONCLUSION

Despite a theoretical maximal dwell time of 6 months, around 50% of all cases are subject to premature stent failure. Predictors of stent failure are bilateral insertion, intrinsic ureteral obstruction, and UTI at the time of tumor stent insertion. Preoperative antibiotic therapy may impact on stent failure rate.

Stenting of Malignant Urinary Tract Obstructions in Humans and Companion Animals

Urine retention secondary to neoplastic obstructions of the upper and lower urinary tracts is a life-threatening condition in both humans and companion animals. Stents can be placed to temporarily or permanently open obstructed urinary tract lumens and are often able to be placed using minimally invasive techniques with guidance via ultrasonography or fluoroscopy. The literature for these techniques is vast for humans and growing for companion animals. The below review provides a discussion of the principles of stenting and types of ureteral and urethral stents, as well as the techniques for placing these stents in humans and companion animals.

Management of complex ischial-urethral fistula in neurogenic patients performing clean intermittent self-catheterization

INTRODUCTION

Neurogenic patients performing clean-intermittent self-catheterization (CIC) may develop an urethral erosion, resulting in ischial-urethral fistulas (I-UF). In this work we present our single-center experience in dealing with this peculiar complication.

METHODS

In this work we included all neurogenic patients performing CIC treated at out Institution for I-UF. All patients had a spinal cord injury or myelomeningocele. We extracted from the patients' medical records the surgical management and postoperative clinical data. We defined failure the persistence of the fistula at X-ray contrast fistulography, retrograde urethrography, or uretrocystoscopy.

RESULTS

We treated 11 patients (8 spinal cord injury, 3 myelomeningocele). Four patients have been treated with the placement of a new generation urethral stent (Uventa) after surgical toilette of the skin ulcer and placement of a temporary suprapubic catheter. All patients demonstrated a complete healing of the urethral lesion at stent removal and continued CIC without any difficulty. Four patients have been treated with perineal urethroplasty, requiring a buccal mucosal graft in two cases. In two patients a suprapubic permanent catheter was placed for a simpler bladder management due to the patients' comorbidities. In one case the incidental finding of an high grade muscle invasive urothelial bladder cancer, made it mandatory to perform an uretheroileocutaneostomy.

CONCLUSIONS

This work represent a unique series of I-UF in neurogenic patients performing CIC. Surgical urethral reconstruction, often with the use of buccal mucosa in large lesions, may be a difficult solution in neurogenic patients, new generation stents (Uventa) represent a minimally invasive, effective, and safe alternative.

New Stent Technologies

Ureteral stents are an indispensable part of any (endo-) urologic practice. Despite the widely demonstrated advantages of stents, they also carry a considerable risk of side effects and complications, such as urinary symptoms, pain, hematuria, decreased quality of life, stent-related infection, and encrustation. Multiple pathways in preventing or mitigating these side effects and complications and improving stent efficacy have been and are being investigated, including stent architecture and design, biomaterials, and coatings. This article provides an update on currently researched and available stents as well as future perspectives.