Advances in ureteral stent design

Outcomes of a non-randomised audit of single pigtail suture stents in urolithiasis management of Asian patients in Singapore

Objective

Double-J (DJ) ureteric stents are commonly placed perioperatively for semirigid or flexible ureteroscopic renal surgery. It is believed that lesser stent material within the bladder mitigates stent-related symptoms. This study aimed to evaluate the J-Fil ureteral stent, a single pigtail suture stent compared with conventional DJ stent in relation to stent symptoms in an Asian population undergoing ureterorenal intervention.

Methods

Based on internal audit committee recommendation approval, the records of 50 patients retrieved, available data of 41 patients who were prospectively enrolled into two groups (Group 1 [J-Fil stent group], n=21 and Group 2 [DJ stent group], n=20) between August 2020 to January 2021, were analysed. Parameters compared were nature of procedure, stone location and size, ease of deployment or removal, and complications. A modified universal stent symptom questionnaire was used to assess morbidity of stent symptoms within 48 h of insertion and at removal.

Results

Both groups had similar median age, distribution in male to female ratio, and stone size. The overall median universal stent symptom questionnaire score at insertion was similar for bladder pain, flank or loin pain, and quality of life between Group 1 and 2; however, at removal Group 1 fared significantly better than Group 2, especially for flank or loin pain and pain at voiding. Both groups had similar ease in insertion with no hospital readmissions.

Conclusion

Our audit favoured the single pigtail suture stent in Asian ureters in mitigating stent-related issues. It showed a good safety profile with easy deployment and removal. It promises a new standard in stenting.

Ureteral stent related symptoms: A comparative study

BACKGROUND

In urology, ureteral stents are used to treat obstructive diseases. Hematuria (54%), fever, discomfort, and lower urinary system symptoms are the predominant symptoms related to ureteral stent.

AIM

This article links stent symptoms to double-j width and length, as well as patient's height, weight, and body mass index (BMI). Ureteric Stent Symptoms Questionnaire (USSQ) was used to measure ureteral stent symptoms at 1st and 4th week of stent in situ as well as the 4th week after pigtail removal.

METHODS

A 200-patient prospective study, where patients were allocated into four groups following ureteral stent insertion depending on the stent characteristics. Those groups were: 4.8 Fr./26 cm (Group A), 4.8 Fr./28 cm (Group B), 6 Fr/26 cm (Group C), and 6 Fr/28 cm (Group D).

RESULTS

Men comprised 53.5% of 200 patients. Participants had an average age of 49 ± 15.5 years, height of 175 ± 8.94 cm, and BMI of 23.8 ± 7.6 cm. The laboratory results were identical between groups. At the first and fourth week, groups had similar urine symptoms, pain severity, health status and occupational activities. The difference in pain location was statistically significant. Group A had 82.4% renal back pain in the first week, whereas Group B had 68.8%, Group C 31.3% and Group D 62.5 (p=0.04). At the fourth week, 64.7% of Group A patients reported kidney front pain, compared to 100% of Group B, 93.3% of Group C, and 100% of Group D (p=0.04). There was statistical significance in the sexual activity of the patients. 24.4% of Group C patients stopped sexual activity before stent installation, compared to 10.6%, 8.3%, and 6.4% of the other groups (p=0.03). A moderate percentage of patients had active sexual activity at week 4 (Group A: 7.8%, Group B: 5.8%, Group C: 8.2%, Group D: 4.1%), p=0.83. In multivariate analysis, urinary catheter group, age, weight, height, and BMI did not significantly affect urine index score (UIS), pain index score (PIS), general health (GH), quality of work (QW), and quality of sex (QS).

CONCLUSIONS

Despite various attempts to establish the best ureteral stent, the effect of double-j stent physical features on stent-related symptoms remained unknown. No verdict is conceivable without adequate empirical data.

Ureteral Stent-Related Symptoms and Pharmacotherapy: A Brief Narrative Review

The purpose of this article is to review the effects of different types of pharmacotherapy on symptoms that affect the quality of a patient's life after stent insertion. A thorough Medline/PubMed nonsystematic review was conducted from 1987 to January 2023, using the terms: "pigtail" OR "ureteral stents" AND "lower urinary tracts symptoms" OR "LUTS" AND "pharmacotherapy" OR "drugs". Relevant studies conducted in humans and reported in English language were included. The available reviews and articles associating the use of drugs with stent-related symptoms (SRS) provide conflicting results. Most of them show a clear benefit of alpha blockers, particularly alfuzosin, on treating urinary SRS, and hence there is a strong recommendation for the use of alpha blockers for the treatment of SRS in the guidelines of the European Association of Urology. Anticholinergics and mirabegron have shown a significant benefit in dealing with irritative bladder symptoms. In contrast, the findings for combination therapies are contradictory, with some studies showing that combination therapy is no superior to monotherapy with regards to most of the subsets of the Ureteral Stent Symptom Questionnaire (USSQ), whereas others present a clear benefit of combination therapies, specifically silodosin and solifenacin, in treating stent-associated lower urinary tract symptoms (LUTS), in comparison with any other type of monotherapy or combination therapy. Many studies suggest that some categories of pharmacotherapy, such as alpha blockers, can alleviate SRS. However, there is conflicting evidence concerning most other types of medical treatment. Randomized trials with the largest number of patients are needed to investigate the effectiveness of novel approaches on SRS.

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.

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.

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

Context

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

Objective

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

Evidence acquisition

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

Evidence synthesis

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

Conclusions

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

Patient summary

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

Developments in Ureteral Stent Technology

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

Functional Properties of Polyurethane Ureteral Stents with PLGA and Papaverine Hydrochloride Coating

Despite the obvious benefits of using ureteral stents to drain the ureters, there is also a risk of complications from 80-90%. The presence of a foreign body in the human body causes disturbances in its proper functioning. It can lead to biofilm formation on the stent surface, which may favor the development of urinary tract infections or the formation of encrustation, as well as stent fragmentation, complicating its subsequent removal. In this work, the effect of the polymeric coating containing the active substance-papaverine hydrochloride on the functional properties of ureteral stents significant for clinical practice were assessed. Methods: The most commonly clinically used polyurethane ureteral Double-J stent was selected for the study. Using the dip-coating method, the surface of the stent was coated with a poly(D,L-lactide-glycolide) (PLGA) coating containing the papaverine hydrochloride (PAP). In particular, strength properties, retention strength of the stent ends, dynamic frictional force, and the fluoroscopic visibility of the stent during X-ray imaging were determined. Results: The analysis of the test results indicates the usefulness of a biodegradable polymer coating containing the active substance for the modification of the surface of polyurethane ureteral stents. The stents coated with PLGA+PAP coating compared to polyurethane stents are characterized by more favorable strength properties, the smaller value of the dynamic frictional force, without reducing the fluoroscopic visibility.

Surface analysis of ureteral stent before and after implantation in the bodies of child patients

The aim of this work was to determine which part of a double-J ureteral stent (DJ stents) showed the highest tendency to crystal, calculi, and biofilm deposition after ureterorenoscopic-lithotripsy procedure (URS-L) to treat calcium oxalate stones. Additionally, the mechanical strength and the stiffness of DJ stents were evaluated before and after exposure to urine. Obtained results indicated that the proximal (renal pelvis) and distal (urinary bladder) part is the most susceptible for post-URS-L fragments and urea salt deposition. Both, the outer and inner surfaces of the DJ ureteral stents were completely covered even after 7 days of implantation. Encrustation of DJ stents during a 31-day period results in reducing the Young’s modulus by 27–30%, which confirms the loss of DJ stent elasticity and increased probability of cracks or interruption. Performed analysis pointed to the need to use an antibacterial coating in the above-mentioned part of the ureteral stent to prolong its usage time and to prevent urinary tract infection.

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.

Comparison of silicone versus polyurethane ureteral stents: a prospective controlled study

BACKGROUND

Approximately 80% of patients with indwelling ureteral stents experience stent related symptoms (SRS). We believe SRS can be reduced through altering the composition of ureteral stents to a less firm material. Therefore, we aim to compare modern silicone and polyurethane ureteral stents in terms of SRS intensity and safety.

METHODS

From June 2018 to October 2018, patients from two distinct clinical centers were prospectively enrolled in the study and stratified (non-randomly) into either control group A, patients who received polyurethane stents (Rüsch, Teleflex), or experimental group B, patients who received silicone stents (Cook Medical). Each participant completed a survey 1 h after stent insertion, in the middle of the stent dwelling period, and before stent removal or ureteroscopy noting body pain and overactive bladder via the visual analog scale pain (VASP) and overactive bladder (OAB) awareness tool, respectively. Additionally, successfulness of stent placement, hematuria, number of unplanned visits, and stent encrustation rates were assessed within each group.

RESULTS

A total of 50 patients participated in the study, control group A consisted of 20 patients and experimental group B consisted of 30 patients. Participants in group B, silicone ureteral stents, demonstrated significantly lower mean values of VASP 2 weeks prior to stent removal and promptly before stent removal (p = 0.023 and p = 0.014, respectively). No other comparisons between the two groups were statistically significant.

CONCLUSIONS

Compared to polyurethane ureteral stents, silicone ureteral stents are associated with lower body pain intensity assessed by VASP 2 weeks before stent removal and at the time of stent removal.

TRIAL REGISTRATION

Current Controlled Trials NCT04000178. Retrospectively registered on June 26, 2019.

Can magnitip double-J stent serve as a substitute for a standard double-J stent?

OBJECTIVE

To evaluate the morbidity of the magnitip double-J stent (DJ), compare its morbidity to the standard stent, and evaluate the possibility of retrieving the magnetic tip of the DJ stent without cystoscopy.

MATERIAL AND METHODS

A total of 50 patients having a lower ureteric stone, who underwent uretroscopic stone retrieval and required the use of a DJ, were randomly assigned to 2 groups, each containing 25 patients. Patients in group A were subjected to exploration with a uretroscope and a magnitip DJ while those in group B received a uretroscope and a standard DJ. The morbidity of both types of DJs was assessed by the Arabic version of the ureteral stent symptom questionnaire (USSQ).

RESULTS

There was a high level of statistically significant differences between the two groups with regards to the total score of the USSQ, which were higher in group A as compared to group B (126.96±14.76 vs. 98.24±12.9) (p=0.001). Further, the cost of the total procedure was significantly higher in group B (9600±1456.59 vs. 8444±783.73) (p=0.001). No statistically significant difference was found between both groups regarding the application, retrieval accuracy, and discomfort caused by DJ removal.

CONCLUSION

The morbidity caused by the magnetic DJ was found to be higher. However, the removal of the magnetic DJ was less costly than the standard DJ.

Large Hepatic Subcapsular Hematoma Secondary to Double-J Stent Placement

Introduction and Background: Urinary diversion with the endoscopic Double-J stent is a frequent procedure; complications can include irritation, suprapubic or flank pain, vesicoureteral reflux, hematuria, or urinary infection. We report a case of hepatic subcapsular hematoma secondary to Double-J stent placement. Case Presentation: A 28-year-old woman presented with a history of Sjögren's disease, nephrocalcinosis, and chronic kidney disease (CKD). The patient underwent multiple percutaneous and endoscopic procedures during the previous 2 years: right kidney: extracorporeal shock wave lithotripsy (SWL) × 4, ureteroscopic lithotripsy × 2, percutaneous nephrolithotomy (PCNL), and retrograde intrarenal surgery; left kidney: SWL × 2, ureteroscopic lithotripsy × 5, and PCNL. Ultrasound imaging showed severe dilation in the right kidney and moderate dilation in the left kidney. CT scanning without contrast revealed a right pyelourethral dilation caused by a 13 mm ureteral lithiasis; also, cortical atrophy was observed. Urosepsis with exacerbated CKD was diagnosed and bilateral 7F Double-J stents were placed on both sides under general anesthesia. On postoperative day (POD) 8, the patient presented with pain in the right hemithorax and dullness to percussion. CT scans showed a heterogeneous hepatic subcapsular collection, of 15 × 7 × 23 cm, of hematic aspect, displacing vascular structures, and no active bleeding. Treatment was expectant and symptomatic. On POD 16, a new CT scan ruled out progression of the hematoma. The patient was finally discharged on POD 19. Four months later, bilateral semirigid ureteroscopy showed a right ureteral lithiasis of 8 × 7 mm, which was fragmented with a holmium laser. Nineteen months after the first episode, the patient is asymptomatic, with no residual lithiasis or hepatic hematoma. Conclusion: This case shows a very rare complication of Double-J stent placement that could be managed by conservative treatment.

Treatment of fragmented and severely encrusted ureteral double-J stent forgotten for 11 years through multimodal endourological methods

Ureteral catheters are frequently used in urology clinics for intrinsic or extrinsic pathologies which cause ureteral obstruction to provide urinary drainage from the kidney to the bladder. With the increase in stent use, an increase is observed in complications occurring due to ureteral stents in direct proportion with this increase, and ureteral double-J (DJ) stents forgotten in the urinary system are observed commonly in urological cases when the patients do not refer to a health institution in this condition and may cause severe problems, such as infection, stent fragmentation, migration, kidney failure, encrustation, and hydronephrosis conditions. A 30-year-old male patient referred to our clinic with right-side pain, dysuria, and incontinence complaints. It was learned that the patient had endoscopic stone surgery due to right ureteral stone and kidney stone 11 years before the presentation. In the imaging methods of the patient, it was observed that the DJ stent forgotten had separated into three parts, and stones were observed in the right ureter. Cystoscopy was made under general anesthesia. The torn distal end of DJ stent was observed in distal urethra. The foreign object was removed with forceps. Then with ureterorenoscope, the stones integrated with the stent at the end of the piece of DJ stent in the ureter were fragmented with pneumolithotriptor. Stone pieces and the second removed part of the stent were extracted with foreign object forceps. Then using nephroscope through percutaneous intervention, the stones at the end of the third torn piece of DJ stent were fragmented with pneumolithotriptor. They were extracted with forceps. After DJ stent installation, each patient should be checked by giving required information and told that the stent must be removed. In cases with forgotten stents and complications, the stents should be removed with suitable medical, endourological, or minimally invasive surgical methods taking care to protect kidney functions.

Advances in Ureteral Stent Design and Materials

Purpose of Review

There are three technological parameters that play a key role on the performance of an ideal stent. These are its material, design and surface coating. This article highlights some fundamental developments that took place in these three areas of stent’s technology, in order to contribute to the identification of an ideal stent.

Recent Findings

In addition to technological developments concerning stent’s material, design and surface coating, the flow dynamic performance of stents has recently attracted increasing attention. Notably, it has been postulated that the local flow field in a stent is correlated with the deposition of crystals and microorganisms. These findings could potentially revolutionise future stent’s designs, and complement developments made on materials and coatings.

Summary

The most relevant changes in materials, designs and surface coatings of ureteric stents are reviewed in this article. These are described in the context of a specific cause of stent’s failure they aim to address, with a particular focus on encrustation and biofilm formation.

Prewire channel stent: a novel stent for bifurcation lesions in a pig model

AIMS

Avoiding side branch occlusion is challenging when treating bifurcation lesions. A newly designed stent system called the prewire channel stent (PWCS) with a side channel positioned between the metallic mesh material and the balloon is introduced. We aimed to compare the time taken to position the PWCS against that for a conventional stent.

METHODS AND RESULTS

The PWCS and a conventional stent were used in a pig model. The time taken from the starting point with the stent outside the body to reaching the bifurcation of the vessel ready for further procedures such as balloon dilatation through the stent mesh opening and double kissing balloon technique, etc., was compared in the conventional stent and PWCS groups. The time taken in the PWCS stent group included the time from sending the stent from outside the body to the desired position of the bifurcation of the vessels of the heart, releasing the stent and pulling back the balloon (SB time). The time taken in the conventional stent included the time from sending the stent from outside the body to the desired position of the bifurcation of the vessels of the heart, releasing the stent, pulling back the balloon (SB time), and wire exchange (WE time). The SB times for the PWCS and the conventional stent groups were not different (28.5±3.8 vs. 25.25±0.75 seconds, n=4). The PWCS group did not have "wire exchange," and had no WE time, which was 28.5±5.7 seconds in the conventional stent group. The total time spent in the PWCS group was 28.5±3.8 seconds, which was shorter than the 53.75±6.2 seconds (n=4, p<0.05) in the conventional stent group.

CONCLUSIONS

The PWCS makes "wire exchange" in the side branch (SB) unnecessary and it can be as easily manipulated as a conventional stent.

Engineering solutions to ureteral stents: material, coating and design

Introduction

An ideal stent would offer simple insertion and removal with no discomfort and/or migration, it would have no biofilm formation or encrustation and would also maintain the patient's quality of life.

Material and methods

In this mini-review, we outlined the engineering developments related to stent material, design and coating.

Results

There have been a wide variety of in-vitro, model-based, animal-based and clinical studies using a range of commercial and non-commercial stents. Ureteric stents have evolved since their first usage with a wider range of stent design, material and coating available for laboratory and clinical use.

Conclusions

While engineering innovations have led to the evolution of stents, more work needs to be done to address the issues relating to stent encrustation and biofilm formation.

Challenges in treatment and diagnosis of forgotten/encrusted double-J ureteral stents: the largest single-center experience

PURPOSE

We aimed to evaluate the effectiveness of the endourologic management of forgotten and/or encrusted ureteral stents together with our single-center experience.

MATERIALS AND METHODS

Fifty-four patients with forgotten double-J ureteral stents were treated in our center between January 2008 and March 2014. Encrustation and the related stone burdens were estimated by using computerized tomography and kidney-ureter-bladder radiography. The management method was chosen based on the stone burden or clinical and radiological findings.

RESULTS

Fifty-four patients, 39 males and 15 females, were included in the study. The average age of the patients was 38.2 ± 25.06 (2-86) years. The average indwelling time of the ureteral stents was 22.6 ± 30.3 (6-144) months. Six of the patients with forgotten stents had solitary kidneys. The double-J stent (DJS) was fragmented in four (7.4%) patients. A urinary system infection was present in 15 (27.7%) of the patients. The ureteral stents and related stones were successfully removed without any complications by combined endourologic techniques to achieve a stone-free state in all patients except for patient with 110 months of forgotten stent time in whom nephrectomy was performed for a nonfunctioning kidney related to the forgotten stent.

CONCLUSIONS

Forgotten/encrusted DJS may lead to complications in a range of urinary system infections, up to a loss of renal function. They can be safely and successfully removed, and the renal function can be preserved by endourologic techniques, starting with the least invasive procedures in centers highly experienced.

Randomized controlled trial to compare the safety and efficacy of tamsulosin, solifenacin, and combination of both in treatment of double-j stent-related lower urinary symptoms

Purpose. We evaluated the effectiveness and safety of tamsulosin, solifenacin, and combination of both in reducing double-J stent-related lower urinary symptoms. Materials and Methods. A total of 338 patients with double-J ureteral stenting were randomly divided, postoperatively, into 4 groups. In group I (n = 84), no treatment was given (control group), group II (n = 85) received tamsulosin 0.4 mg daily, group III (n = 84) received solifenacin 10 mg daily, and group IV (n = 85) received a combination of both medications. Before insertion and 2 weeks after, all patients completed the International Prostate Symptom Score (IPSS), quality of life component of the IPSS (IPSS/Qol), Overactive Bladder Questionnaire (OAB-q), and Visual Analogue Pain Scale (VAPS) questionnaire. Results. The demographics and preoperative questionnaires scores of all groups were comparable. There were statistically significant differences in all scores in favour of groups II, III, and IV as compared to control group (P value < 0.005). Group IV showed statistically significant differences in total IPSS, QoL score, and OAB-q score as compared to groups II and III (P value < 0.001). Conclusions. Combined therapy of tamsulosin and solifenacin significantly alleviated lower urinary symptoms associated with double-J stents as compared to either medication alone.

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

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

Assessment of bio-safety of low-cost polyurethane urologic stents used in developing countries

Background:

Ureteral stents, despite their ubiquitous use, have not been evaluated for their safety and strength after removal from the patient. While literature is available from the industry with regards to manufacturing and specifications of stents, what happens to a stent after it is inserted into the body, still needs to be explored.

Materials and Methods:

We conducted a methodical study of 153 consecutive patients with urological problems who were stented with inexpensive polyurethane stents. Once removed from the patients, the stents were analyzed for breakload, tensile strength, elongation, pH, decomposition temperature, residue as well as diameter change.

Results:

There was no significant change in the physical and mechanical properties of the stent after clinical use and the variance was within the acceptable range of biomaterials. There was minimal leaching of material and color change in all stents.

Conclusion:

The cheap polyurethane stents were found to be safe for use in patients, for the short time periods of in situ stenting. The degradation of physical and chemical properties of the stent was not significant. Thus it can be safely said that the stents currently in widespread use are cost-effective and physically safe for short spans of time.

Single session removal of forgotten encrusted ureteral stents: combined endourological approach

Forgotten ureteral stents represent a difficult problem for urologists; the major complications are infection, migration, encrustation, stone formation, and multifractured stent, and a consensus on the best therapeutic approach is lacking. Here we present our experience with endoscopic management of this challenging problem and discuss the various endourological approaches for treating forgotten encrusted ureteral stents. From January 2005 to December 2010, 19 patients (11 women and 8 men) with encrusted ureteral stents were retrospectively analyzed. Combined endourologic therapies including extracorporeal shock wave lithotripsy (SWL), percutaneous nephrolithotomy (PCNL), ureterorenoscopic lithotripsy (URSL), and cystolithotripsy (CLT) were used to achieve stent removal. A total of 19 patients with encrusted ureteral stents were treated at our center. The mean patient age was 46.2 ± 18.5 years (8-81), the average indwelling time of the stent was 24.7 ± 19.0 months (8-93), and the mean hospital stay was 3.4 ± 4.0 days (range 1-15 days). Using the described combination of techniques, all stents and the associated stones were eventually removed without any complications and patients were rendered stone- and stent-free. A main element of the treatment strategy was to keep the number of interventions as low as possible. The use of various combinations of endourological techniques can achieve effective stent and stone treatment after a single anesthesia session with minimal morbidity and short hospital stay.

Ureteral stents: new ideas, new designs

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

Effectiveness of medical treatment in overcoming the ureteral double-J stent related symptoms

BACKGROUND

We investigated whether the frequency of lower urinary tract symptoms (LUTS) increased in patients in whom double-J stents were applied. We also evaluated several medical therapy protocols to treat symptoms related with ureteral stents.

MATERIALS AND METHODS

A total of 108 patients, in whom unilateral double-j stent was applied during ureteral stone treatment, were included. Before the double-J stent was applied, all patients completed storage components of the "International Prostate Symptom Score" (IPSSs), quality of life components of the IPSS (IPSS-QOL) and "Overactive Bladder Questionnaire" (OABq) forms and scores were calculated. After the procedure, cases were randomized into 5 groups, an antiinflammatory was given to Group 1, spasmolytic to Group 2, anticholinergic to Group 3 and α-blocker to Group 4. No additional drug was given to Group 5 as this control group. During the fourth week of the procedure, IPSSs, IPSS-QOL and OABq forms were again completed and scores were compared with the previous ones.

RESULTS

When all the cases were evaluated, the IPSSs, IPSS-QOL and OABq scores of patients in whom the double-J stent was applied were statistically significantly higher the procedure. Compared to the control group, the cases where the double-J stent was applied showed a higher IPSSs, IPSS-QOL and OABq scores and none of the medical therapies could prevent this increase.

INTERPRETATION

The frequency of LUTS increased in cases where the ureteral stent was applied and discomfort continued as long as the stent stayed in the body.

Effects of tamsulosin, solifenacin, and combination therapy for the treatment of ureteral stent related discomforts

Purpose

To evaluate the effect of tamsulosin, solifenacin, and combination therapy of two agents in improving the lower urinary tract symptoms of patients with indwelling double-J ureteral stents.

Materials and Methods

A total of 168 patients underwent placement of a double-J ureteral stent after retrograde ureteroscopy for urinary stone disease. All patients received polyurethane double-J ureteral stents (6 Fr, 24 or 26 cm), which were removed a mean of 14 days postoperatively. A total of 48 patients were given no medication (Group 1), 43 patients were given tamsulosin 0.2 mg once daily (Group 2), 45 patients were given solifenacin 5 mg once daily (Group 3), and 32 patients were given a combination of two agents postoperatively (Group 4). International Prostate Symptom Score/quality of life (IPSS/QoL) and visual analogue pain scale (VAPS) questionnaires were completed by each patient at 1 day postoperatively and on the day of stent removal.

Results

In the total group of patients, the mean age was 50.24±12.90 years. There was a significant difference in the IPSS total score between group 1 and groups 3 and 4. Group 4 also differed significantly from group 1 in the irritative subscore. The obstructive subscore differed between groups 2 and 4 and group 1. There was a statistically significant difference between group 1 and group 4 in the QoL score. There were no significant differences in the VAPS.

Conclusions

Combination therapy with tamsulosin and solifenacin improved both irritative and obstructive symptoms more than in the other groups. Combination therapy should be strongly considered for patients who complain of stent-related symptoms.

Ureteral stent discomfort: Etiology and management

Objectives:

To review the evidence-based literature on the causes, characteristics, and options to manage double J stent-related symptoms.

Methods:

We performed a Medline database assessment on papers that investigated the prevalence, mechanisms, risk factors, bothersome and management of double-J stent-related symptoms. Articles in English were reviewed and summarized.

Results:

Stent-related symptoms have a high prevalence and may affect over 80% of patients. They include irritative voiding symptoms including frequency, urgency, dysuria, incomplete emptying; flank and suprapubic pain; incontinence, and hematuria. Assessment tools are important to determine their intensity and allow for comparisons between different points in the timeline. The Urinary Stent Symptom Questionnaire (USSQ) is the most proper tool used for this purpose. Management should be focused on the prevention and management of symptoms. In this sense, research has focused on new materials and stent designs that would be more compatible to the physiologic properties of the urinary tract and medications that can ameliorate the sensitivity and motor response of the bladder.

Conclusions:

Stent-related symptoms are very common in the Urological clinical setting. It is of major importance for the urologist to understand their physiopathology and to be familiar with ways to avoid or manage them.

Introduction to biodegradable polylactic acid ureteral stent application for treatment of ureteral war injury

OBJECTIVE

• To study the operability and effectiveness of a biodegradable ureteral stent for clinical treatment of ureteral war injury using a canine model.

MATERIALS AND METHODS

• A device was designed and employed to generate firearm fragment wounds in unilateral ureters (on randomly chosen sides) of nine beagles (Group A). The wounded ureters were then debrided and sutured. • Intravenous pyelography (IVP) and radioactive renography were performed 40, 80 and 120 days postoperatively. In Group B, firearm fragment wounds were made to the bilateral ureters in nine beagles. A polylactic acid stent was placed unilaterally (on a randomly chosen side) whereas the ureter on the other side was debrided and sutured without stenting. • Both IVP and radioactive renography were performed 40, 80 and 120 days postoperatively. The operability and effectiveness of the biodegradable ureteral stent were studied thereafter.

RESULTS

• In Group A, hydronephrosis and hydroureter occurred and worsened postoperatively on the wounded sides in all nine beagles. The ratio of the renal partial concentration indices (RPCI) between the kidneys (unwounded side : wounded side) increased. • The ratio of the kidney washout half-time between the kidneys (unwounded side : wounded side) decreased. In Group B, neither hydronephrosis nor hydroureter was found postoperatively in the stented ureters but both occurred in the unstented ureters in all nine beagles. • The ratio of RPCI between kidneys (stented side : unstented side) increased whereas the kidney washout half-time ratio between the stented and unstented sides decreased. Differences were significant.

CONCLUSION

• In Group A, the new canine model for firearm fragment wounds was tested and proved to be operable and effective. In Group B, hydronephrosis and hydroureter were effectively prevented in ureters by biodegradable stent placement compared with the non-stented ureters where hydronephrosis and hydroureter occurred. The renal concentration capacity was effectively protected and the half-time of kidney washout was shortened.

Efficacy of tamsulosin 0.4 mg/day in relieving double-J stent-related symptoms: a randomized controlled study

This study evaluated the efficacy of tamsulosin in improving stent-related symptoms and quality of life in patients with in-dwelling double-J ureteral stents. A total of 42 patients (15 males and 27 females) with ureteral stent placement following ureteroscopy, percutaneous nephrolithotomy or balloon dilatation, were prospectively randomized into two groups of 21 patients. Group I received 0.4 mg tamsulosin once daily for 4 weeks and group II was a non-placebo, non-treatment control. All patients completed the International Prostate Symptom Score (IPSS) and SF-36 questionnaires at 2 and 4 weeks post-operatively. The IPSS scores for irritative and obstructive symptoms were significantly lower in group I than group II at both 2 and 4 weeks. Among the eight domains of SF-36, role limitation due to physical health and bodily pain was significantly better in group I at 2 and 4 weeks. General health was also significantly better in group I at 2 weeks. Tamsulosin improved both urinary symptoms and quality of life without causing serious side-effects.

Multimodal stone therapy for two forgotten and encrusted ureteral stents: a case report

Introduction

Ureteral stent placement is a common procedure in daily urologic practice. To manage the problems of forgotten stents for many years needs multimodal stone therapy.

Case presentation

We present a case of a 26-years-old Caucasian, white woman with two forgotten encrusted ureteral stents for 48 months. Multimodal stone therapy including extracorporeal shock wave (SWL), percutaneous nephrolithotomy (PCNL), ureterorenoscopy (URS), cystolithotripsy with Lithoclast, and open surgery was necessary to remove all the stones. Using the described combination of techniques, our patient was rendered stone and stent free. Urologists should bear in mind the presence of severe encrustations when they have to deal with a forgotten stent.

Conclusion

This case shows that combined urologic techniques can achieve successful and safe management of forgotten stents, but treatment should be tailored to the volume of encrustation and associated stone.

In vitro simulation of stent fracture mechanisms in ureteric nitinol wire stents

The ZebraStent is a new-concept lumen-less teflon-coated nitinol double-J wire-stent, designed to facilitate the passage of residual fragments after extracorporeal shock wave lithotripsy. In clinical practice we observed a small number of stent fractures. Hence, an experimental model was designed to simulate the physical forces that may lead to material fatigue of the stent. Flexion force was simulated by "half circular kidney mimicking structures" (HCKMS) into which the upper part of the stent was placed. All experiments were done for a minimum of 5 million cycles representing a stent indwelling time of 9 months, or until stent fracture, and simulating respiratory kidney movement. It was demonstrated that as the diameter of the HCKMS decreases, thus leading to an increased bending of the stent, the likelihood of stent fracture increased proportionally and occurred earlier. From our results it appears that stent fractures can be avoided by observing a maximum indwelling time of 6-8 weeks (which should suffice for the duration of a average SWL treatment), by choosing the correct (and shortest possible) stent length, and perhaps by manufacturer's modifications decreasing the stent's resistance to flexion. The ZebraStent concept remains appealing if it is considered as a short-term stent for post-SWL residual fragments.

Investigation of a novel degradable ureteral stent in a porcine model

PURPOSE

Ureteral stents often result in patient morbidity and the potential for a forgotten stent. When the suture tether is detached, a secondary procedure is required for removal. Previous attempts at developing biodegradable ureteral stents have been unsuccessful since those stents were not biocompatible or they failed to degrade in timely fashion. We evaluated a new biodegradable Double-J stent in a porcine model.

MATERIALS AND METHODS

A total of 36 Yorkshire pigs were stented unilaterally with a biodegradable Uriprene stent or a standard biostable control stent. Excretory urograms, and blood and urine tests were performed at weeks 2, 3, 4, 5, 7 and 10. Four animals per group were sacrificed after 2, 4, 7 and 10 weeks to determine stent degradation and obtain samples for pathological evaluation.

RESULTS

Degradable ureteral stents began to degrade at 3 weeks. By weeks 7 and 10, 60% and 100% of the stents, respectively, were fully degraded. There was no significant difference in laboratory parameters or the amount of hydronephrosis between the 2 groups. However, ureteral dilatation was significantly more pronounced in the control group than in the Uriprene group. The novel stent was biocompatible on histological evaluation and it led to significantly less urinary tract infections than in controls.

CONCLUSIONS

The novel Uriprene stents provided drainage similar to that of regular stents and they were completely degraded by 10 weeks. Moreover, these stents resulted in less ureteral dilatation and fewer positive urine cultures. Biocompatibility was good and human trials will be forthcoming.

Malignant extrinsic ureteral obstruction: a survey of urologists and medical oncologists regarding treatment patterns and preferences

OBJECTIVES

To investigate and compare practice patterns regarding malignant extrinsic ureteral obstruction among urologists (GU) and oncologists (ONC).

METHODS

We invited members of the American Urological Association and the American Society of Clinical Oncologists to participate in a web-based survey. Participants gave recommendations in clinical scenarios, as well as opinions regarding use of ureteral stents and nephrostomy tubes (PCN).

RESULTS

The survey was randomly sent to 1500 GU and 1500 ONC, of whom 226 (15%) and 191 (12.4%) responded, respectively. The groups significantly varied in treatment preferences in all clinical scenarios. Regarding stent failure, ONC preferred PCN (79% versus GU 62%); GU (18% versus 5%) next preferred stent manipulation (eg, increase stent size, dual stents) (P <0.0001). The greatest risk of stents per GU was decreased quality of life (65% versus 13%), whereas ONC were most concerned about infection (43% versus 3%) (P <0.0001). The greatest risk of PCN per GU was dislodgement (48% versus 18%), whereas ONC were most concerned about infection (40% versus 8%) (P <0.0001).

CONCLUSIONS

Practice patterns vary significantly between GU and ONC in the treatment of malignant extrinsic ureteral obstruction. Further investigation and collaboration are necessary to determine which interventions are best for these patients and how to ensure consistency in their care.

Management of forgotten ureteral stents with holmium laser

Forgotten ureteral stents represent a difficult problem for urologists, and a consensus on the best therapeutic approach is lacking. We present our experience with endoscopic management of this challenging problem and discuss the chosen treatment combinations. We retrospectively reviewed records of the management of eight cases of forgotten stents between 2002 and 2007. The mean patient age was 41.1 years (21 years to 68 years), and the mean duration of stents in the urinary system was 16.1 months (7 months to 3 years). The stents were severely calcified and encrusted in all patients. Advanced renal failure secondary to hydronephrosis because of severe encrustation and stone formation over the stent was seen in two patients. Four patients were treated with percutaneous nephrolithotomy (PCNL) alone, two were treated with PCNL and ureteroscopy (URS), and the other two underwent a combination of extracorporeal shock wave lithotripsy (ESWL) and URS .All stents and the associated stones were eventually removed without any complications. Combined endourologic techniques with holmium laser can achieve safe removal of forgotten stents if treatment is tailored to the volume of encrustation and associated stone. Imaging evaluation and documentation of urine cultures with negative findings are imperative prior to any attempt to remove the stent.

Preventing the Forgotten Ureteral Stent: Implementation of a Web-Based Stent Registry with Automatic Recall Application

OBJECTIVES

To describe and analyze a unique computerized system that tracks ureteral stents and automatically sends a notice by e-mail to clinical staff if a stent becomes overdue for removal.

METHODS

We have developed an electronic stent register (ESR) and stent extraction reminder facility (SERF) located within our hospital computer network. After stent insertion, a stent "episode" is created in the ESR with a mandatory maximal stent life (MSL). The SERF interrogates the ESR on a daily basis and identifies stents that have breached its MSL, generating daily e-mail notices to personnel until the stent is removed and the ESR updated. The episode data capture initially employing manual entry was changed to barcode technology acquisition. We analyzed the success of patient recall and conducted a prospective, blinded review to determine the success of the data acquisition.

RESULTS

A total of 293 episodes were created within 2.4 years. Of the 241 (86%) episodes that were closed, 123 (51%) went beyond the MSL. The mean delay from designated MSL to stent removal was 20.89 days (SD 19.71). In the 7 months before barcode data acquisition, 43 of 71 stents were entered into the ESR (data capture rate 61%). In the 7 months after barcode data acquisition, 52 of 60 stents were entered (data capture rate 87%; P = 0.0009).

CONCLUSIONS

The results of our study have shown the ESR and SERF to be robust and valuable tools for the treatment of patients with ureteral stents. Barcode acquisition significantly improved the stent insertion capture rate. This system ensures improved patient safety with an element of protection from potential litigation.

Forgotten, encrusted ureteral stents: a challenging problem with an endourologic solution

BACKGROUND AND PURPOSE

Forgotten, encrusted ureteral stents represent a difficult problem for urologists, and a consensus on the best therapeutic approach is lacking. We present our experience with endoscopic management of this challenging problem and discuss the chosen treatment combinations.

PATIENTS AND METHODS

Five women and four men aged 31 to 71 years (mean 50.2 years) with 10 stents indwelling for 6 to 85 months (mean 24.1 months) were treated in our department. Stent encrustation and the associated stone burden were evaluated by plain radiographs and intravenous urography. Treatment decisions were based on the clinical presentation and imaging findings. Three stents in two patients had minimal or slight encrustations.

RESULTS

The mean number of procedures per patient was 2.1 (range 1-4). Percutaneous nephrolithotomy was performed in eight patients and retrograde ureteroscopy with or without intracorporeal lithotripsy in seven cases. Cystolitholapaxy or percutaneous cystolithotripsy was used to manage the distal portion of the encrusted stent in two cases. Extracorporeal shockwave lithotripsy was performed in only two patients. All stents and the associated stones were eventually removed without any complications.

CONCLUSIONS

Combined endourologic techniques can achieve safe removal of forgotten stents if treatment is tailored to the volume of encrustation and associated stone. Imaging evaluation and documentation of negative urine culture are imperative prior to any attempt to remove the stent.

Granulation encapsulated stent: a new therapeutic approach for vascular implantation

OBJECTIVES

To determine if stents could be encapsulated with immunocompatible granulation tissue for the treatment of vascular diseases.

METHODS

Bare metal stents were implanted in New Zealand white rabbits so they would be encapsulated with immunocompatible granulation tissue. The granulation encapsulated stents (GES) were then treated with either mitomycin C or saline, and implanted into rabbit iliac arteries for 4 weeks. To test whether the effect of mitomycin C was retained, we co-cultured smooth muscle cells for 3 h with subcutaneous tissue (as control) or with granulation tissue from GES treated with mitomycin C and saline.

RESULTS

Vessels with GES treated with mitomycin C (MS) and washed with saline had significantly less neointimal area (NA) after 4 weeks (0.27 (SD 0.03) mm(2) than vessels containing bare metal stents (B) (1.15 (SD 0.10) mm(2), n = 5, p<0.05) or GES treated with saline (S) (4.78 (SD 0.72) mm(2), n = 5, p<0.05). The average vessel injury score was not significantly different among these three groups (S: 1.98 (SD 0.51), MS: 1.46 (SD 0.18) and B: 1.51 (SD 0.32)). GES treated with saline had significantly less NA than the other two groups and also blocked blood flow in the contralateral iliac artery in the abdominal aortic bifurcation immediately after implantation and 4 weeks later. Histology also showed neointimal overgrowth in the vessel wall over the contralateral iliac artery.

CONCLUSIONS

GES treated with mitomycin C can significantly inhibit neointimal formation in rabbit arteries due to the formation of granulation tissue. GES treated with saline demonstrated significantly increased NA and resisted normal rabbit artery pressures.

Complications of 2735 retrograde semirigid ureteroscopy procedures: a single-center experience

BACKGROUND AND PURPOSE

Ureteroscopy is nowadays one of the techniques most widely used for upper urinary- tract pathology. Our goal is to describe its complications in a large series of patients.

PATIENTS AND METHODS

Between June 1994 and February 2005, 2436 patients aged 5 to 87 years underwent retrograde ureteroscopy (2735 procedures) under video and fluoroscopic assistance. We used semirigid ureteroscopes (8/9.8F Wolf, 6.5F Olympus, 8F and 10F Storz) for 384 diagnostic and 2351 therapeutic procedures. Upper urinary-tract lithiasis (2041 cases), ureteropelvic junction stenosis (95 cases), benign ureteral stenosis (29 cases), tumoral extrinsic ureteral stenosis (84 cases), iatrogenic trauma (35 cases), superficial ureteral tumors (16 cases), superficial pelvic tumors (7 cases), and ascending displaced stents (44 cases) were the indications. The mean follow-up period was 56 months (range 4-112 months).

RESULTS

The rate of intraoperative incidents was 5.9% (162 cases). Intraoperative incidents consisted of the impossibility of accessing calculi (3.7%), trapped stone extractors (0.7%), equipment damage (0.7%), and double- J stent malpositioning (0.76%). In addition, migration of calculi or stone fragments during lithotripsy was apparent in 116 cases (4.24%). The general rate of intraoperative complications was 3.6% (98 cases). We also saw mucosal injury (abrasion [1.5%] or false passage [1%]), ureteral perforation (0.65%), extraureteral stone migration (0.18%), bleeding (0.1%), and ureteral avulsions (0.11%). Early complications were described in 10.64%: fever or sepsis (1.13%), persistent hematuria (2.04%), renal colic (2.23%), migrated double-J stent (0.66%), and transitory vesicoureteral reflux (4.58%, especially in cases with indwelling double-J stents). We also found late complications such as ureteral stenosis (3 cases) and persistent vesicoureteral reflux (2 cases). Most (87%) of the complications followed ureteroscopic therapy for stones. Three fourths (76%) of the complications occurred in the first 5 years of the series.

CONCLUSIONS

According to our experience, mastery of ureteroscopic technique allows the urologist to proceed endourologically with minimum morbidity. Despite the new smaller semirigid instruments, this minimally invasive maneuver may sometimes be aggressive, and adequate training is imperative.

Aging assessment by dynamic mechanical analysis of in vivo encrusted polymeric urinary stents

PURPOSE

To investigate the viscoelastic properties of plastic pigtail stents after removal from patients using the method of dynamic mechanical analysis (DMA).

MATERIALS AND METHODS

Dynamic mechanical analysis was performed in 12 polymeric pigtail stents left indwelling for various periods of time (0-120 days). The encrustations were characterized by infrared spectroscopy, and their morphology was observed using scanning electron microscopy.

RESULTS

Softening and stiffening behavior was observed. Stiffening was found specifically in the stents with heavy mineral deposits.

CONCLUSIONS

Material degradation becomes obvious after certain periods of time. The effect of stent degradation appeared in two forms: softening of the stent polymer, possibly through interaction with urine, and stiffening of the stent secondary to the formation of various insoluble mineral deposits covered by layers of organic matrix.