The optimal stent pusher position to achieve successful ureteral stent insertion under fluoroscopic guidance

Objective: To examine factors to predict the optimal stent pusher position when inserting ureteral stents under fluoroscopy.Methods: We retrospectively reviewed 327 patients who underwent ureteral stent insertion. We considered the pubic bone as a useful anatomical landmark to insert ureteral stents under fluoroscopic guidance. Thus, we categorized patients into three groups (proximal, middle, and distal groups) according to the position of the radiopaque tip of the push catheter when inserting the ureteral stent. Success was defined as a completely curled ureteral stent tail. We compared stent insertion success rates among the three groups. A multivariate analysis was performed to identify the factors affecting stent insertion success.Results: In men, 36 (63.2%) cases were deemed successful in the proximal group compared with 40 (80.0%) cases in the middle group and 12 (20.7%) cases in the distal group (p<0.001). In women, 26 (45.6%) cases were deemed successful in the proximal group compared with 54 (98.2%) cases in the middle group and 38 (76.0%) cases in the distal group (p<0.001). With the multivariate analysis, the stent pusher position was the most significant factor influencing successful stent insertion (men: odds ratio 6.00, 95% confidence interval 2.66-13.51, p<0.001;women: odds ratio 37.80, 95% confidence interval 4.94-289.22, p<0.001).Conclusion: The position of the stent pusher affects stent insertion success. The middle of the pubic symphysis is the optimal position for the radiopaque tip of the pusher when inserting ureteral stents under fluoroscopic guidance.

Percutaneous nephrostomy versus ureteral stent in hydronephrosis secondary to obstructive urolithiasis:A systematic review and meta-analysis

Objective: To assess if there is a preferable intervention between retrograde ureteral stent (RUS) and percutaneous nephrostomy (PCN) tube, in cases of upper urinary tract stone obstruction with complications requiring urgent drainage, by evaluating outcomes regarding urinary symptoms, quality of life (QoL), spontaneous stone passage, and length of hospital stays, since there is no literature stating the superiority of one modality over the other.Methods: We searched MEDLINE and other sources for relevant articles in June 2019 without any date restrictions or filters applied. The selection was done first by the title and abstract screening and then by full-text assessment for eligibility. Only randomized controlled trials or cohort studies in patients with hydronephrosis secondary to obstructive urolithiasis that presented comparative data between PCN and RUS placement concerning at least one of the defined outcome measures were included. Lastly, MEDLINE database and PubMed platform were screened again using the same terms, from June 2019 until November 2022.Results: Of 556 initial articles, seven were included in this review. Most works were considered of moderate-to-high quality. Three studies regarding QoL showed a tendency against stenting, even though only one demonstrated statistically significant negative impact on overall health state. Two works reported significantly more post-intervention urinary symptoms in stenting patients. One article found that PCN is a significant predictor of spontaneous stone passage, when adjusted for stone size and location. Findings on length of hospital stays were not consistent among articles.Conclusion: PCN appears to be the intervention better tolerated, with less impact on the patient’s perceived QoL and less post-operative urinary symptoms, in comparison with RUS. Nevertheless, further studies with larger samples and a randomized controlled design are suggested.

Compression Mechanical Performance Simulation and Parameter Optimization of Degradable Ureteral Stent Based on ABAQUS

The compression performance of a degradable ureteral stent is analyzed and the parameters are optimized by a finite element modeling method.The degradable ureteral stent explored in this paper is developed from poly(glycolic acid)(PGA)and poly(lactic-co-glycolic acid)(PLGA)degradable materials.Based on the actual measurement of fabric structure parameters,the three-dimensional model of the stent is established with the help of the modeling software.The finite element analysis software is used to simulate the compression process of the degradable ureteral stent.The parameters of materials,interactions and boundary conditions are set according to the compression environment of the stent for modeling and simulation.On this basis,the friction coefficient of yarns,the yarn radius,and the braided angle of the stent are further compared.The comparison test is carried out by a single variable.The experimental results show that the change of yarn friction coefficient has little influence on the compressive stress,while the yarn radius and the braided angle of the stent have a great influence on the compressive stress.

Understanding the corrosion of Mg alloys in in vitro urinary tract conditions: A step forward towards a biodegradable metallic ureteral stent

Ureteral stents play a fundamental role in modern time urology. However, following the deployment, stent-related symptoms are frequent and affect patient health and quality of life. Using biodegradable metals as ureteral stent materials have emerged as a promising strategy, mainly due to the improved radial force and slower degradation rate expected. Therefore, this study aimed to characterize different biodegradable metals in urinary tract environment to understand their propensity for future utilization as base materials for ureteral stents. The corrosion of 5 Mg alloys - AZ31, Mg-1Zn, Mg-1Y, pure Mg, and Mg-4Ag - under simulated urinary tract conditions was accessed. The corrosion layer of the different alloys presented common elements, such as Mg(OH)_(2), MgO, and phosphate-containing products, but slight variations in their chemical compositions were detected. The corrosion rate of the different metals varied, which was expected given the differences in the corrosion layers. On top of this, the findings of this study highlighted the significant differences in the samples' corrosion and corrosion layers when in stagnant and flowing conditions. With the results of this study, we concluded that Mg-1Zn and Mg-4Ag presented a higher propensity for localized corrosion, probably due to a less protective corrosion layer;Mg-4Ag corroded faster than all the other four alloys,and Mg-1Y stood out due to its distinct corrosion pattern, that showed to be more homogeneous than all the other four samples, making this one more attractive for the future studies on biodegradable metals.

Ureteral stents in urolithiasis

Ever since the ureteral stent design was fitted with a curl on both sides to prevent it from migrating up or down the ureter some 40 years ago,its use has gained tremendous momentum,aiding in the rise and evolution of endourology and has confidently kept its place in modern time urology.Over the past four decades,several designs,coating and biomaterials have been developed,trying to reduce infection,encrustation and other stent related symptoms.As the ideal stent has not yet been discovered,different ways of helping patients with their complaints have been researched.This review will cover these aspects of stent use in urolithiasis.

Stents for malignant ureteral obstruction

Malignant ureteral obstruction can result in renal dysfunction or urosepsis and can limit the physician’s ability to treat the underlying cancer.There are multiple methods to deal with ureteral obstruction including regular polymeric double J stents(DJS),tandem DJS,nephrostomy tubes,and then more specialized products such as solid metal stents(e.g.,Resonance Stent,Cook Medical)and polyurethane stents reinforced with nickel-titanium(e.g.,UVENTA stents,TaeWoong Medical).In patients who require long-term stenting,a nephrostomy tube could be transformed subcutaneously into an extra-anatomic stent that is then inserted into the bladder subcutaneously.We outline the most recent developments published since 2012 and report on identifiable risk factors that predict for failure of urinary drainage.These failures are typically a sign of cancer progression and the natural history of the disease rather than the individual type of drainage device.Factors that were identified to predict drainage failure included low serum albumin,bilateral hydronephrosis,elevated C-reactive protein,and the presence of pleural effusion.Head-to-head studies show that metal stents are superior to polymeric DJS in terms of maintaining patency.Discussions with the patient should take into consideration the frequency that exchanges will be needed,the need for externalized hardware(with nephrostomy tubes),or severe urinary symptoms in the case of internal DJS.This review will highlight the current state of diversions in the setting of malignant ureteral obstruction.

Effect of Media on the in vitro Degradation of Biodegradable Ureteral Stent

The biodegradable ureteral stent should retain their supporting properties for defined period and then gradually degrade to small particles with the flow of urine. The mechanism and process of the stent's degradation should be investigated and understood well due to its direct impact on the stents' usage. An enhanced braidbased degradable ureteral stent composed of poly-glycolic acid(PGA) and the copolymer of lactic and glycolic acid(PGLA) was evaluated in vitro in this study with four kinds of degradable media:human urine(HU,pH = 7. 4),artificial urine(AU,pH = 5. 8),and phosphate buffer solutions( PBS,pH = 5. 8 and 7. 4) so as to compare the effects of media on the degradation of stents. The mechanical properties and morphology were observed at different degradaing time intervals of 0,7,14,21,28,and 35 d. The in vitro degradation behaviors of stents in four kinds of media were extremely different. The degradation rate of stents in HU was the highest. The impact of media's pH to the degradation is not obvious while the components in the media contribute much to the difference.

Effect of Preoperative Double-J Ureteral Stenting before Flexible Ureterorenoscopy on Stone-free Rates and Complications

The effect of preoperative Double-J(DJ)ureteral stenting before flexible ureterorenoscopy(FURS)in the treatment for urinary stones was evaluated.We retrospectively enrolled 306 consecutive patients who underwent FURS from Jan.2014 to Dec.2017.All the patients were classified into two groups according to whether they had DJ ureteral stenting before FURS.Baseline characteristics(age,sex,stone location,stone size,surgical success rate,operation time,stone-free rate of the first day after surgery,stone-free rate of the first month after surgery,total complication rate)were compared using Chi-square test for categorical variables and Kruskal-Wallis test for continuous variables.In total,306 patients were included in this study.The group of DJ stenting before FURS included 203(66.3%)patients,and non-DJ stenting before FURS was observed in 103(33.7%)patients.The group of DJ stenting before FURS was significantly associated with a shorter operation time(53.8 vs.59.3 min,P<0.001),a higher stone-free rate of the first day after surgery(69.0%vs.51.5%,P=0.003).However,statistical significant differences were not found in the age,sex,stone location,stone size,surgical success rate,stone-free rate of the first month after surgery(89.2%vs.81.6%,P=0.065)and total complication rate(5.4%vs.9.7%,P=0.161)between the two groups.Preoperative DJ ureteral stenting before FURS could reduce the operation time and increase stone-free rate of the first day after surgery.However,it might not benefit the stone-free rate of the first month after surgery and reduce the complication rate.Preoperative DJ stenting should be not routinely performed.

Use of percutaneous nephrostomy and ureteral stenting in management of ureteral obstruction

The management options for ureteral obstruction are diverse, including retrograde ureteral stent insertion or antegrade nephrostomy placement, with or without eventual antegrade stent insertion. There is currently no consensus on the ideal treatment or treatment pathway for ureteral obstruction owing, in part, to the varied etiologies of obstruction and diversity of institutional practices. Additionally, different clinicians such as internists, urologists, oncologists and radiologists are often involved in the care of patients with ureteral obstruction and may have differing opinions concerning the best management strategy. The purpose of this manuscript was to review available literature that compares percutaneous nephrostomy placement vs ureteral stenting in the management of ureteral obstruction from both benign and malignant etiologies.

Ureteral Stent Fragmentation:a Case Report and Review of Literature

SINCE the introduction of double J stents in 1978, ureteral stents have become an integral tool in treating ureteral obstruction from calculi and other causes.1 Owing to the widespread usageof indwelling ureteral catheters, a number of possible complications such as migration, infection, pyelonephritis, breakage, encrustation, stone formation, and ureteral stents fragmentation have been noted.2 Of all the complications, ureteral stent fragmentation was sporadically reported and believed to be rare. Here we present a case of fragmentation of a new type of double J stent, which was used to provide free drainage to the bladder after balloon dilation.

Ureteral Stenting Following Uncomplicated Ureteroscopy for Ureteric Stones: A Randomized Controlled Trial

Objective: The objective is to assess the benefits and adverse effects of routine ureteral stenting after uncomplicated ureteroscopic lithotripsy. Material and Methods: Sixty patients with ureteric calculi amenable to ureteroscopic lithotripsy were randomized to an unstented (30 patients) or a stented (30 patients) treatment group, standard ureteroscopic lithotripsy done using 8 French semirigid ureteroscope, and pneumatic lithotripter used to fragment the stones. They were followed up for postoperative flank pain, lower urinary tract symptoms (LUTS) and hematuria. Results: There was no significant difference in the mean age (stenting 37.8 year and 33.5 year unstenting) of patients, gender and stone size in both groups. No significant difference in the mean flank pain within 3 days postoperative, while at day 14 postoperative flank pain for stenting group was significant (P = 0.03). Dysuria and urgency were high for stenting group (P = 0.002 and 0.011). Hematuria within 3 and 14 days was higher in the stenting group. Conclusion: After uncomplicated ureteroscopy, stents can be safely omitted. Unstented patients have significantly fewer LUTS, haematuria and flank pain.

Characterization of ureteral stents by dual-energy computed tomography: Clinical implications

Dual-energy computed-tomography(DECT) has been suggested as the method of choice for imaging urinary calculi due to the modality's high sensitivity for detect-ing stones and its capability of accurately differentiat-ing between uric-acid(UA) and non-UA(predominantly calcium) stones. The clinical significance of the latter feature relates to the differences in management of UA vs non-UA calculi. Like calculi, ureteral stents are assigned color by the dual-energy post-processing algorithm, which may lead to improved or worsened stone visualization based on the resulting stent/stone contrast. Herein we depict the case of a nephrolithiasis patient with bilateral stents, each with different color, clearly displaying the effect of stent color on stone vi-sualization. Further, three-dimensional reconstruction of the DECT images illustrates advantages of this enhancement compared to conventional two-dimensional computed tomography. The resulting stent/stone contrast produces an unanticipated potential advantage of DECT in patients with urolithiasis and stents and may promote improved management decision-making.

Huge encrusted ureteral stent forgotten for over 25 years:A case report

BACKGROUND Ureteral stent insertion is a relatively non-invasive procedure commonly used in the field of urology to resolve urinary obstruction.However,they are sometimes forgotten and the risk of complications increases with time.CASE SUMMARY A 43-year-old woman with a history of recurrent urinary tract infections visited our hospital for evaluation of persistent left flank pain,and lower urinary tract symptoms despite anti-biotic treatment.She had received urological surgery in her teens but did not know the details of her surgery.Kidney,ureter,and bladder X-ray and abdominopelvic computed tomography revealed a forgotten left ureteral stent with huge encrustation at both ends and a severely dilated left kidney with parenchymal thinning.In order to remove the ureteral stent,a laparoscopic nephroureterectomy was planned.The ureteral stent was successfully removed,and she was discharged after recovery.The patient was followed up for two years after surgery and did not show any signs of long-term complications.CONCLUSION Long indwelling stents can cause dire complications requiring radical interventions.Stent registry systems,novel stent material development,and proper patient education is important for complication prevention.

In vitro Degradation Study of a Braided Thin-Walled Biodegradable Ureteral Stent

The main disadvantage of conventional ureteral stents commonly used to provide urinary drainage after urological practice is that the patients have to undergo a secondary surgical procedure to remove stents. A new braided thin-walled biodegradable ureteral stent composed of PGA （ polyglycolic acid） and PLGA （ eopolymer of polylactic and polygiycolic acid） mnltifilaments was evaluated in v/tro in this study. In vitro degradation was performed in artificial urine with pH of 5.8 and the temperature of 37~C. The mass loss, mechanical properties, and morphology were observed at different degradaing time intervals of 0, 1, 2, 3, 4, and 5 weeks. The stent had a thinner wail than those of other degradable stents and provided better mechanical properties. The braided thin-walled biodegradable ureteral stents began to degrade after 2 weeks. At the week of 5, the stents were fully degraded. The degradative process of stents is smooth and well controlled.

Peak stent discomfort occurs early and ureteral stent with distal loop design has less paineA pilot prospective randomised singleblinded trial over 2 weeks

Objectives:The Polarisloop ureteric stent reduces the severity of stent discomfort by minimising stent material in the bladder.Early impact of ureteral stenting on quality of life(QoL)within 1 week remains unclear.The usefulness of the patient-administered ureteral stent symptoms questionnaire(USSQ)during this period of stent insertion was assessed.In this pilot single-blinded prospective randomised study,we investigate 1)the presence of early(within the 1st week)stent discomfort via the visual analog scale(VAS);2)determine the QoL of the loop stent against conventional stent.Methods:Forty adults requiring retrograde unilateral ureteral stent placements were enrolled.Patients with single ureteric stone or benign stricture were selected.Patients were randomised in 1:1 ratio to the loop and pigtail arm.The USSQ was administered before placement(baseline),USSQ and VAS were administered on Day 3,7,and 14.Results:There were no significant differences between the USSQ scores.Median pain scores on Day 3 were lower in the loop stent group(2.9 vs.4.0,pZ0.047).There was a significant reduction in pain from Day 3e7(0 vs.1,pZ0.016)in the pigtail group.Conclusions:Our results suggest that peak stent discomfort occurs but resolves quickly within 1 week of post-stent insertion.The loop stent offers a better pain profile compared with conventional stents at Day 3 but no difference in QoL.The loop stent reduces early pain experience post-stent insertion and may have a role in the care of patients who experience significant stent discomfort previously.

Metallic ureteral stent in restoring kidney function: Nine case reports

BACKGROUND Retroperitoneal fibrosis is an exceptionally rare disease characterized by proliferation of fibrous tissue and inflammation in the retroperitoneum.It features many symptoms in the kidneys and in other organs and usually leads to ureteral obstruction.CASE SUMMARY Here we present 9 consecutive cases of idiopathic retroperitoneal fibrosis(IRPF)in patients who presented to the Department of Nephrology or Department of Rheumatology,Xuanwu Hospital,Capital Medical University,Beijing,China,between January 2012 and June 2017 with ureteral obstruction due to external compression of the ureter that led to hydronephrosis and kidney dysfunction.Computed tomography imaging was used to identify hydronephrosis and ureteral obstruction and to evaluate kidney function.Each patient was diagnosed with IRPF based on clinical observation and computed tomography examination results.To restore kidney function,a retrograde metallic stent was placed in the ureter under X-ray guidance 2 d after each patient’s admission.No perioperative complications occurred in any patient,but postoperative complications occurred in two patients as follows:Patient 2 had stent migration and repeated metallic stent infections that resolved with treatment;and patient 4 had postoperative hematuria because he resumed normal activities too soon after stent placement(contrary to instruction).Placement of the metallic ureteral stents provided relief from ureteral obstruction and restored kidney function in all patients.CONCLUSION Our 9-case series underscores the utility and efficacy of applying the Resonance®metallic ureteral stent to treat ureteral obstruction in patients with IRPF.For all retroperitoneal fibrosis cases in our series,ureteral stents provided effective relief and were shown to reduce the incidence rate of perioperative and postoperative complications.

Does delaying ureteral stent placement lead to higher rates of preoperative acute pyelonephritis during pregnancy?

BACKGROUND Pregnancy with renal colic may cause pyelonephritis,decreased renal function,systemic infection and even shock in pregnant women,and cause premature birth and other adverse pregnancy outcomes.When surgery is necessary,the relationship between timing of the operation and the outcome of the mother and child are not known.AIM To investigate the association between time to ureteral stent placement and clinical outcomes of patients with renal colic during pregnancy.METHODS In this retrospective study,pregnant women with renal colic who underwent surgery were studied.Maternal preoperative acute pyelonephritis(PANP),pregnancy outcome,and length of hospital stay(LOS)were compared between the two groups.RESULTS 100 patients were included in the analysis,median age was 30 years.Median time to ureteral stent placement was 48 h(interquartile range,25-96 h),and 32 patients(32%)were diagnosed with PANP.PANP was closely related to hospitalization costs,re-admission to the hospital due to urinary tract infection after surgery and premature delivery.Multivariate analysis found that stone location and time from pain to admission were related to PANP.CONCLUSION Both early and delayed surgery are safe and effective for the treatment of renal colic during pregnancy.Early surgery may be superior to a delayed procedure due to shorter LOS.For pregnant patients with renal colic,delayed surgery within 48 h is not related to the clinical outcome of the mother and child.However,the time from pain to hospital admission was related to PANP.

Forgotten Ureteral Stents in a Tertiary Hospital in Accra and a Review of Endourological Management of Upper Urinary Tract Pathologies in the West Africa Sub-Region

Background: Forgotten ureteral stent is defined as prolong indwelling ureteral stent whose function is no longer desired. Ureteral stents are used in the management of upper urinary tract pathologies. Prolonged indwelling ureteral stents may be complicated by urosepsis or renal failure, encrustation, stone formation, spontaneous fracture which may either be retained or voided in the urine (stenturia). Hitherto, these complications were managed by open procedures alone in our center. We report our recent experience in endourology with the management of three cases of forgotten ureteral stents with durations of ten years and two years (two cases) and review endourological practice in West Africa. Conclusion: Although encrusted stents can be managed successfully by minimally invasive approaches in the majority of cases, the best treatment is prevention. Urology units should have preferably an electronic stent register such that when the time for removal is due, the patient's name and details are flagged red. If electronic register is not available, then a hard paper/book register should be made to prevent situations of forgotten stents. Also, efforts must be made to improve endourological services in the West Africa subregion to allow patients to have the benefit of endourology in the management of upper urinary tract pathologies including that of stones originating from an encrusted or fractured forgotten ureteral stent.

Multi-objective structural optimization and degradation model of magnesium alloy ureteral stent

Background:Mg alloys have attractive properties,including biocompatibility,biodegradability,and ideal mechanical properties.Moreover,Mg alloys are regarded as one of the promising candidates for manufacturing ureteral stents.This study proposed a multi-objective optimization method based on the Kriging surrogate model,NSGA-III,and finite element analysis to improve the degradation performance of Mg alloy ureteral stents.Methods:The finite element model for the degradation of Mg alloy ureteral stents has been established to compare the degradation performance of the stents under different parameters.Latin hypercube sampling was adopted to generate train sample points in the design space.Meanwhile,the Kriging surrogate model was constructed between strut parameters and stent degradation behavior.The NSGA-III was utilized to determine the optimal solution in the global design space.Results:The optimized stent achieved 5.52degradation uniformity(M),10degradation time(DT),and 4work time(FT).The errors between the Kriging surrogate model and the finite element calculation results were less than 6%.Conclusion:The optimized stent achieved better degradation performance.The degradation behavior of stents was dependent on the design parameters.The multi-objective optimization method based on the Kriging surrogate model and finite element analysis was effective in stent design optimization problems.

Repair of a common bile duct defect with a decellularized ureteral graft

AIM To evaluate the feasibility of repairing a common bile duct defect with a decellularized ureteral graft in a porcine model.METHODS Eighteen pigs were randomly divided into three groups. An approximately 1 cm segment of the common bile duct was excised from all the pigs. The defect was repaired using a 2 cm long decellularized ureteral graft over a T-tube(T-tube group, n = 6) or a silicone stent(stent group, n = 6). Six pigs underwent bile duct reconstruction with a graft alone(stentless group). The surviving animals were euthanized at 3 mo. Specimens of the common bile ducts were obtained for histological analysis.RESULTS The animals in the T-tube and stent groups survived until sacrifice. The blood test results were normal in both groups. The histology results showed a biliary epithelial layer covering the neo-bile duct. In contrast, all the animals in the stentless group died due to biliary peritonitis and cholangitis within two months post-surgery. Neither biliary epithelial cells nor accessory glands were observed at the graft sites in the stentless group.CONCLUSION Repair of a common bile duct defect with a decellularized ureteral graft appears to be feasible. A T-tube or intraluminal stent was necessary to reduce postoperative complications.