Multicenter Experience of the Newly Designed Covered Metallic Ureteral Stent for Malignant Ureteral Occlusion: Comparison With Double J Stent Insertion

Management of neglected and fragmented DJ stent with severe encrustation and stone: A case report

INTRODUCTION AND IMPORTANCE

DJ stents are widely used in urological procedures and interventions. One of the main problems associated with DJ stent is encrustation and stone formation. The main risk factor for Forgotten, encrusted and calcified (FECal) stent is duration of the stent placement. In addition to high index of suspicion, Imaging like U/S and CT scan are important diagnostic modality. Multiple endourologic and open procedure may be needed for management of fecal stent.

CASE PRESENTATION

This case report is to discuss a 23 years old female patient with a neglected stent after right pyelolithotomy was done 6 years back. The presence of the stent was identified incidentally after she visited local health facility for recurrent LUTS. The CT scan shows fragmented and encrusted stent with in the bladder and pelvis, stones in stent coils and isolated lower pole stone. She was managed by a procedure of cystolithotomy and right PCNL in separate sessions.

CLINICAL DISCUSSION

Common complication of DJ stent placement especially if left for long duration is encrustation, stent migration, fragmentation and stone formation. Patient or relatives unawareness about the stent placement is the most important cause for neglecting stent. Multiple Endourologic procedures may be needed for the management of FECal stent. However some resource limited settings do combination of endourologic and open surgery.

CONCLUSION

Minimizing the duration of the stent especially for patient with risk factors is advised to decrease encrustation. Since management of FECal stent is challenging both for patient and urologists, prevention is the way to tackle it. Multiple procedures may be required to manage FECal stent.

Prediction of Stent Failure for Malignant Ureteral Obstruction in Non-Urological Cancer

PURPOSE

To analyze prognostic factors associated with ureteral stent failure and to develop a prediction model for malignant ureteral obstruction (MUO) in patients with non-urological cancers.

MATERIALS AND METHODS

We retrospectively reviewed patients with non-urological cancers who underwent ureteral stenting or percutaneous nephrostomy (PCN) for MUO between 2006 and 2014. Variables predicting stent failure were identified using Cox regression analysis.

RESULTS

Of the 743 patients, 468 (63.0%) underwent ureteral stenting only, and 275 (37.0%) underwent PCN owing to technical (n=215) or functional (n=60) stent failure. The median overall survival was 4 [interquartile range (IQR) 1-11] months, and the median interval duration to stent failure was 2 (IQR 0-7) months. In univariate analysis, lower gastrointestinal cancer, previous radiotherapy to the pelvis, bladder invasion, lower ureteral obstruction, and low previous estimated glomerular filtration rate (eGFR) (<30 mL/min/1.73 m²) were significantly associated with a decreased survival rate. In multivariate analysis, bladder invasion and previous eGFR were significant predictors. With these two predictors, we divided patients into three groups based on their presence: low-risk (neither factor; n=516), intermediate-risk (one factor; n=206), and high-risk (both factors; n=21). The median stent failure-free survival rates of patients in the low-, intermediate-, and high-risk groups were 26 (8-unreached), 1 (0-18), and 0 (0-0) months, respectively (p<0.001).

CONCLUSION

In cases of ureteral obstruction caused by non-urological cancers, patients with bladder invasion and a low eGFR showed poor stent failure-free survival. Therefore, PCN should be considered the primary procedure for these patients.

Inner surface modification of polyurethane ureteral stents using plasma-enhanced chemical vapor deposition to improve the resistance to encrustation in a pig model

PURPOSE

We developed a ureteral stent with a non-fouling inner surface using plasma micro-surface modification technology. This study aimed to evaluate the safety and efficacy of this stent in animal model.

MATERIALS AND METHODS

Ureteral stents were placed in five Yorkshire pigs. A bare stent was inserted on one side and an inner surface-modified stent was inserted on the other side. Two weeks after stenting, laparotomy was performed to harvest the ureteral stents. The changes in the inner surface were grossly evaluated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). In addition, if encrustation was observed, the components were analyzed using Fourier transform infrared spectroscopy. Urine cultures were used for safety assessment.

RESULTS

In all models, urine cultures did not show any bacterial growth before and after stenting, and stent-related complications were not identified. Hard materials were palpable in four bare models. Palpable material was not identified in the modified stent. Calcium oxalate dihydrate/uric acid stones were identified in two bare stents. In the SEM images with EDS, biofilm formation was confirmed in the bare stents. Biofilm formation was significantly less on the inner surface of the modified stent, and the intact surface of the modified stent was larger than that of the bare stent.

CONCLUSIONS

The application of a specialized, plasma-enhanced, chemical vapor deposition technology to the inner surface of ureteral stents was safe and showed resistance to biofilm formation and encrustation.

Inner surface modification of ureteral stent polyurethane tubes based by plasma-enhanced chemical vapor deposition to reduce encrustation and biofilm formation

Encrustation and/or biofilm formation in ureteral stents are major causes of obstruction and reduce the lifetime of a ureteral stent. In this study, the inner surfaces of polyurethane (PU) tubes (inner and outer diameters of 1.2 and 2.0 mm, respectively) were reformed with Ar, O₂, and C₂H₂ gases using specialized plasma-enhanced chemical vapor deposition techniques for the first time. Then, the modified PU tubes were immersed in urine for 15 days, and the characteristics of the inner surfaces were analyzed. Depending on the modification procedure, the corresponding inner surface exhibited different chemical properties and different rates of encrustation and biofilm formation. For a hydrophilic surface treated with Ar and O₂, encrustation and biofilm formation increased, while for the C₂H₂ coating, the development of encrustation and biofilm reduced by more than five times compared with the untreated bare PU tube. This study demonstrated that inner plasma surface modification of ureteral stents greatly enhances resistance to encrustation and biofilm formation.

Occlusive Properties of Transrenal Ureteral Occlusion Self-Expandable Metallic Stents: 3D-Printed Phantom and Ex Vivo Studies

Newly developed transrenal ureteral occlusion self-expanding metallic stents (SEMSs) are applied in patients with inoperable fistulas. In this study, the occlusive properties of M- and D-type occlusion SEMSs were investigated in 3D-printed phantom and ex vivo porcine urinary tracts. In the former, the mean bursting pressure causing leakage of contrast medium through the occlusion SEMS was relatively higher in M-types (42.8 ± 3.8 mmHg) than in D-types (38.8 ± 3.8 mmHg), without a statistical difference (p = 0.075). In the latter, the bursting pressure causing leakage through the M-type occlusion SEMS (110.7 ± 8.6 mmHg) was significantly higher than that of the D-type occlusion SEMS (93.8 ± 11.2 mmHg, p = 0.015); however, the mean bursting pressures causing contrast blowout did not differ between the two types (178.7 ± 11.2 mmHg vs. 176.2 ± 11.8 mmHg, p = 0.715). In conclusion, M- and D-type occlusion SEMSs showed similar efficacy in occlusive properties in the 3D phantom study; however, the M-type was superior in the ex vivo porcine urinary tract model. Further in vivo experimental studies are required to confirm these experimental results.

Comparison of a covered metallic ureteral stent and a double-J stent for malignant ureteral obstruction in advanced gastric cancer

AIM

To compare the patency and safety of covered metallic stents (CMS) and the double-J stent (DJS) for treating malignant ureteral obstruction (MUO) in advanced gastric cancer (AGC).

MATERIALS AND METHODS

Between 2016 and 2018, the medical records of 61 patients (84 ureters; CMS, 39 patients, 54 ureters; DJS, 22 patients, 30 ureters) with MUO caused by AGC were reviewed retrospectively. The Kaplan-Meier method and log-rank test were used to evaluate differences of primary or assisted primary patency between groups. Cox regression was conducted separately for early (within 7 days) and late (after 7 days) primary patency.

RESULTS

Technical success of CMS placement was 100% (54/54) and 96.8% (29/30) for DJS (p=0.357). The cumulative stent patency rates at 1, 3, 6, and 12 months were 77%, 74%, 70%, and 70%, in the CMS group and 72%, 60%, 53%, and 26%, in the DJS group. Apart from the period within 7 days (p=0.784), primary patency was consistently higher in the CMS group when compared to the DJS group over the entire follow-up period (p=0.034). Assisted primary patency was consistently higher in the CMS group than in the DJS group over the entire follow-up period (p=0.001). The CMS group was more likely to have complications than the DJS group (48.1% versus 16.7%, p=0.004). Complications were minor, self-limiting events such as haematuria/haematoma.

CONCLUSION

CMS had better late patency and assisted primary patency than DJS. Procedure-related minor complications more frequently occurred with CMS.

Numerical Analysis of Urine Flow with Multiple Sizes of Double-J Stents

This study investigated which sizes of double-J stents are more effective in achieving an acceptable urine flow through stenotic and stented ureters. Sixty four computational fluid dynamics models of the combinations of two different gauge ureters (4.57 mm and 5.39 mm in diameter) with four different levels of ureteral and four different sizes of double-J stents were developed for the numerical analysis of urine flow in the ureter. Luminal, extraluminal, and total flow rates along the ureter were measured, and the flow patterns around the ports and side holes were investigated. For the 4.57-mm ureter, the total flow rate for each gauge of stent was 23–63 mL/h (5 Fr), 20–47 mL/h (6 Fr), 17–35 mL/h (7 Fr), and 16–26 mL/h (8 Fr) and for the 5.39-mm ureter, the total flow rate for each gauge of stent was 43–147 mL/h (5 Fr), 36–116 mL/h (6 Fr), 29–92 mL/h (7 Fr), and 26–71 mL/h (8 Fr). With a 74% stenosis, all stents allowed a low flow rate, and the differences in flow rates between the stents were small. At the other levels of stenosis, 5 Fr stents allowed greater flow rates than the 8 Fr stents. The luminal flow rate increased just before the area of stenosis and decreased after the stenosis because of the increase and decrease in the luminal flow through the side holes before and after the stenosis. Therefore, a larger double-J stent is not favorable in achieving an acceptable urine flow through the stenotic and stented ureters. The results in this study could not be necessarily correlated with clinical situation because peristalsis, viscosity of the urine and real format of the ureter were not considered in our model. In vivo experiments are necessary for confirmation of our findings. Double J stents are commonly used in the ureteral stenosis or occlusion, especially due to ureter stones which obstruct the flow of urine. Clinicians choose the size of double J stent on the basis of their clinical experience. Here, we tried to know which sizes of double J stents are better for sufficient urine flow. According to various documents that try to determine the optimal shape of double J stents to increase the urine flow through the ureter, mostly bigger stent is recommended to occur maximum urine flow. However, in case of ureter with stenosis or occlusion, the right size of the double J stent may vary depending on the degree of stenosis in the ureter. To find appropriate stent size for the ureter with stenosis, computational fluid dynamics was conducted. This study shows that smaller diameter stents are more appropriate than larger diameter stents depending on the situation.

Stenting Using the Rendezvous Technique for Postoperative Ureteral Complications in Cancer Patients

PURPOSE

This study aimed to retrospectively evaluate the safety and efficacy of ureteral stent placement using the rendezvous technique for the treatment of postoperative ureteral complications in cancer patients.

MATERIALS AND METHODS

From January 2005 to April 2015, 19 patients (2 men and 17 women; median age, 59; range, 42-79 years old) with unilateral ureteral lesions (ureteral leakages in 6, strictures in 4, and both in 9) underwent ureteral stent placement using the rendezvous technique. Percutaneous nephrostomy was performed, and stent placement was attempted via antegrade and retrograde approaches. The technical success, procedure-related complications, and clinical success were retrospectively analyzed.

RESULTS

The median follow-up period was 29.8 months (range, 0.3-116.5 months). The ureteral stent placement was successful in 17 out of 19 patients (89.5%). Double J ureteral stent was used in 6 patients, and straight catheter as an internal-external nephro-ureteral stent was used in 11 patients. The rendezvous technique was used in the retroperitoneal space and urinary tract in 6 and 11 patients, respectively. No major complications related to the rendezvous technique occurred. Finally, 4 patients achieved stent-free condition (21.1%), and periodic stent exchange was continued in 9 (47.4%). However, permanent external drainage and surgical reconstruction were needed in 4 (21.1%) and 2 (10.5%) patients, respectively. The final clinical success rate was 68.4% (13 out of 19 patients).

CONCLUSION

Ureteral stent placement using the rendezvous technique for the treatment of postoperative ureteral complications in cancer patients is safe and may be alternative to permanent external drainage and invasive surgical reconstruction.

LEVEL OF EVIDENCE

Level 4, Case series.

Management and treatment options when facing malignant ureteral obstruction

Malignant ureteral obstruction is an unfortunate finding that can be caused by a wide-ranging number of malignancies with a prognosis of limited survival. Given its presentation and progression, it can be refractory to treatment by traditional single polymeric ureteral stents. With a higher failure rate than causes of benign ureteral obstruction, a number of other options are available for initial management, as well as in cases of first-line therapy failure, including tandem stents, metallic stents, percutaneous nephrostomies and extra-anatomic stents. We reviewed the literature and carried out a PubMed search including the following keywords and phrases: "malignant ureteral obstruction," "tandem ureteral stents," "metallic ureteral stents," "resonance stent," "metal mesh ureteral stents" and "extra-anatomic stents." The vast majority of studies were small and retrospective, with a large number of studies related to metallic stents. Given the heterogenous patient population and diversity of practice, it is difficult to truly assess the efficacy of each method. As there are no guidelines or major head-to-head prospective trials involving these techniques, it makes practicing up to the specific provider. However, this article attempts to provide a framework with which the urologist who is presented with malignant ureteral obstruction can plan in order to provide the individualized care on a case-by-case basis. What is clear is that prospective, randomized clinical trials are necessary to help bring evidence-based medicine and guidelines for patients with malignant ureteral obstruction.

Malignant ureteral obstruction: experience and comparative analysis of metallic versus ordinary polymer ureteral stents

BACKGROUND

To study the outcome and experience of using metallic stents in treating patients with malignant ureteral obstruction (MUO).

METHODS

Seventy-six patients with MUO were assigned to the metallic stent group (MSG) or the ordinary polymer stent group (OPSG) according to the different materials. The success rate of the operation, duration of operation, patency rate serum creatinine values ,postoperative complications and QOL scores were compared between the two groups.

RESULTS

In the OPSG and MSG, the success rates of the operation were 95.5% and 96.9%, respectively, and the durations of the operation were 20.6 ± 2.2 min and 50.9 ± 10.3 min (P < 0.01), respectively. There was no significant difference between the groups in serum creatinine values at 3 days after the operation (P > 0.05); however, the creatinine values at 3 days after the operation decreased significantly compared with those before the operation (P < 0.01). In the OPSG, there was no significant difference in creatinine values between 3 days and 6 months after operation, while the creatinine values 1 year after operation were increased significantly compared to those at 3 days after the operation (P < 0.05). In the MSG, there was no significant difference among creatinine values at different intervals (P > 0.05). The total rate of post-procedural complication was lower in the MSG than that in the OPSG(P < 0.05). There was no significant difference in the QOL score between the two groups before the operation (P > 0.05); however, the QOL scores at 6 months and 1 year after the operation were higher in the MSG than that in the OPSG(P < 0.05). In the MSG, there was no significant difference in the QOL score between preoperation and 6 months after surgery. Similarly, there was also no difference in the QOL score between 6 months after surgery and 1 year after surgery(P > 0.05). On the contrary, the differences of QOL score in the OPSG group were much significant between disparate time intervals (P < 0.05).

CONCLUSIONS

For patients with MUO who require long-term retention of the stent, metallic stents with longer indwelling time are superior to ordinary polymeric stents.

Treatment outcomes of ureteral stenting for malignant extrinsic ureteral obstruction: a comparison between polymeric and metallic stents

Purpose

To compare treatment outcomes, more specifically patency rate, of polymeric and metallic stents for malignant ureteral obstruction.

Patients and methods

Between August 2007 and September 2017, we retrospectively analyzed the data of 92 patients (126 ureters) having a diagnosis of malignant extrinsic ureteral obstruction treated with indwelling ureteral stents (polymeric and full-length metallic stents). Of these patients, 35 (54 ureters) were treated with polymeric stents and 57 (72 ureters) with a Resonance® metallic stent. The observation period was censored to 1 year. Survival rate in cases of malignant ureteral obstruction was calculated, and the relationship between the causes of ureteral obstruction, the stent type, and the patency rate was evaluated.

Results

The median observation period was 145 days, with a median survival time of 258 days. The stent patency rate was 70.9% at 1 year, regardless of stent type. Stent occlusion was observed in 20 patients (33 ureters). According to stent type, occlusion of the polymeric and metallic stents was identified in 12 (22%) and 8 (11%) cases, respectively. The clinical features associated with stent failure were assessed. In univariate analysis, the patency rate was significantly better for the metallic stent than for the polymeric stent (1-year patency rate; 78.4%, 61.1%, respectively, HR, 2.15; 95% CI, 1.07-4.33; p=0.031). However, the patency rate among patients with abdominal dissemination, lymph node metastasis, and direct compression by tumor was not significantly different.

Conclusion

Indwelling ureteral stents, particularly metallic stents, are effective for the treatment of malignant ureteral obstruction.

Metallic Ureteric Stents in Malignant Ureteric Obstruction: A Systematic Review

The effectiveness of metallic stents in the management of malignant ureteric obstruction is unclear. This systematic review evaluates the use of 4 commercially available metallic stents (Resonance, Memokath 051, Uventa, and Allium URS). Twenty-one studies met eligibility criteria. Overall success rates ranged from 88% for the Allium stent to 65% for Memokath 051. Resonance demonstrated the lowest migration rate (1%). Uventa had the lowest obstruction rate (6%). Metallic ureteric stents offer a viable alternative in the management of malignant ureteric obstruction. Further high quality studies are required to assess cost effectiveness and refine specific indications based on etiology and level of the ureteric obstruction.

Comparison of single and tandem ureteral stenting for malignant ureteral obstruction: a prospective study of 104 patients

OBJECTIVES

The aim of this study was to compare single and tandem ureteral stenting in the management of malignant ureteral obstruction (MUO).

METHODS

Our hospital's institutional review board approved this prospective study. Between November 2014 and June 2017, single ureteral stenting was performed in 56 patients (94 renal units) and tandem ureteral stenting in 48 patients (63 renal units) for MUO. A comparative analysis of the technical success rate, patient survival, stent patency, and complications was performed.

RESULTS

Similar demographic data were observed in patients receiving either single or tandem ureteral stenting. The technical success rate was 93.6% (88/94) for single ureteral stenting and 95.2% (60/63) for tandem ureteral stenting. There was no difference in overall survival between patients receiving single or tandem ureteral stenting (p = 0.41), but the duration of stent patency in tandem ureteral stenting was significantly longer (p = 0.022). The mean patency time was 176.7 ± 21.3 days for single ureteral stenting, and 214.7 ± 21.0 days for tandem ureteral stenting. The complications of ureteral stenting were urinary tract infection (n = 18), lower urinary tract symptoms (n = 5), haematuria (n = 3), and stent migration (n = 1).

CONCLUSIONS

Tandem ureteral stenting is a safe and feasible treatment for MUO, and had better efficacy compared to single ureteral stenting.

KEY POINTS

• Ureteral stenting is an established treatment for the management of malignant ureteral obstruction (MUO) • Prospective single-centre study showed that tandem ureteral stenting is a safe and feasible treatment for MUO • Tandem ureteral stenting provides longer stent patency compared to single ureteral stenting in patient with MUO.

A Prospective Randomized Comparison of a Covered Metallic Ureteral Stent and a Double-J Stent for Malignant Ureteral Obstruction

Objective

To compare the safety and efficacy between a covered metallic ureteral stent (CMS) and a double-J ureteral stent (DJS) for the treatment of a malignant ureteral obstruction (MUO).

Materials and Methods

Nineteen patients (seven men and 12 women; mean age, 53.4 years) were randomly assigned to the CMS (n = 10) or DJS (n = 9) group. The following were compared between the two groups: technical success, i.e., successful stent placement into desired locations; stent malfunction; stent patency, i.e., no obstruction and no additional intervention; complications; and patient survival.

Results

The technical success rate was 100% in all 10 and 12 ureteral units in the CMS and DJS groups, respectively. During the mean follow-up period of 253.9 days (range, 63–655 days), stent malfunction was observed in 40.0% (4/10) and 66.7% (8/12) in the CMS and DJS groups, respectively. In the per-ureteral analysis, the median patency time was 239.0 days and 80.0 days in the CMS and DJS groups, respectively. The CMS group yielded higher patency rates compared with the DJS group at three months (90% vs. 35%) and at six months (57% vs. 21%). The overall patency rates were significantly higher in the CMS group (p = 0.041). Complications included the migration of two metallic stents in one patient in the CMS group, which were removed in a retrograde manner. The two patient groups did not differ significantly regarding their overall survival rates (p = 0.286).

Conclusion

Covered metallic ureteral stent may be effective for MUO.

Application of resonance metallic stents for malignant ureteral obstruction

Purpose: To determine the effectiveness of the Resonance metallic stent in treating malignant ureteral obstruction (MUO) and clarify the risk factors that lead to stent failure. Material and methods: We retrospectively identified and analyzed the records of patients who had MUO and underwent placement of Resonance metallic stents from November 2014 to June 2017 in our hospital. Stent failure was defined as unexpected interventions including stent exchange, need of percutaneous nephrostomies (PCN) or ureterocutaneostomy. Results: A total of 22 stents were placed in 14 patients with MUO. The median follow-up was 145 days (4.8 months) and the maximum duration of stenting was 21.3 months. The technique success rate was 100%. Two patients experienced early postoperative increasing creatinine with oliguria but only one of them failed to achieve primary patency. The overall success rate was 90% (9/10). Conclusion: Resonance metallic stent is a safe and effective treatment for MUO and can maintain durable patency over 12 months. Preoperative urinary tract infection (UTI) and tumor invasion into the bladder are considered as risk factors of stent blockage and failure. Early postoperative elevated creatinine oliguria, suggestive with intrarenal and prerenal disease, should not be deemed to be stent failure.

The effectiveness of ureteric metal stents in malignant ureteric obstructions: A systematic review

Objective

To review the literature on the effectiveness, safety and long-term patency of ureteric metal mesh stents (MSs), as a variety of MSs have been used for managing malignant ureteric obstruction over the last three decades.

Materials and methods

A systematic review using the search string; Ureter∗ AND (stent OR endoprosthesis) AND metal∗ was conducted on PubMed, Scopus, Web of science and Cochrane Library online databases in May 2016. Prospective, retrospective, and comparative studies including MSs were included. The primary endpoint was the patency rate and the secondary endpoint was complications.

Results

In all, 324 publications were screened and 31 articles were included in the systematic review; 21 prospective and 10 retrospective studies. These studies reported the effectiveness of specific MSs in population studies, in comparative studies among different MSs, as well as among MSs and JJ stents. It should be noted that all comparative studies were retrospective.

Conclusion

The experiences with vascular MSs, such as the Wallstent™ (Boston Scientific/Microvasive, Natick, MA, USA), were related to high occlusion rates, due to endoluminal hyperplasia, and long-term disappointing patency. The use of covered MSs designed for the vascular system was also unfavourable. The Memokath 051™ (PNN Medical A/S, Kvistgaard, Denmark) had better patency rates, but also higher migration rates. The long-term results were acceptable and rendered the Memokath 051 as a viable option for the management of malignant ureteric obstruction. The Uventa™ (Taewoong Medical, Seoul, Korea) and Allium™ (Allium Medical Solutions Ltd, Caesarea, Israel) MSs, specifically designed for ureteric placement, provided promising results. Nevertheless, the wide acceptance of these MSs would require well-designed clinical studies and long-term follow-up.

Tandem ureteral stents in the management of double-J stent dysfunction in gynecological malignancies

PURPOSE

The goal of this study was to determine the efficacy and safety of tandem ureteral stent placement in the management of malignant ureteral obstruction (MUO) refractory to single ureteral double-J stent drainage in women with gynecological malignancies.

MATERIALS AND METHODS

A retrospective study was performed on 14 women (mean age, 54.5±9.6 [SD] years; range: 38-70 years) who had tandem stent placement following failed single ureteral double-J stent placement from 2012 to 2017. Survival analyses were performed with Kaplan-Meier method.

RESULTS

Twenty-nine successful procedures were performed on 19 ureters (19 primary stent placement and 9 exchange procedures). Technical success of primary tandem stent placement was 95% (19/20 procedures). Mean follow-up was 180.1±173.7 (SD) days (range: 62-616 days). Median estimated survival of the patients was 118 days (Q1: 261, Q3: 95; range: 62-616 days). Primary stent failure rate was 25% and assisted stent failure rate was 21.4%. There was no significant difference among survival of patients with and without tandem stent failure. Mean estimated primary stent patency and assisted stent patency were 171.4±13.8 (SD) days and 409.9±59.8 (SD) days, respectively. Four patients underwent 1 to 3 stent exchanges. Median exchange time was 181 days (Q1: 151, Q3: 191, range: 141-214 days) and technical success rate was 100%. Grade 2 and 3 complication rates were 25% and 3.6%, respectively.

CONCLUSION

Tandem ureteral stent placement is a feasible, safe and effective procedure for the management of failed ureteral double-J stent placement in women with gynecological malignancies.

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.

Fluoroscopy Guided Transurethral Placement of Ureteral Metallic Stents

Ureteral stent exchange is usually performed under both fluoroscopic and cystoscopic guidance. We experienced two cases with retrograde placement of metallic ureteral stent via urethra under fluoroscopic guidance. When patients with double-J ureteral stent (DJUS)have symptom and want to change DJUS to metallic stent, fluoroscopic guided transurethral placement of ureteral metallic stent is a good option as alternative of cystoscopic procedure or percutaneous procedure through percutaneous nephrostomy tract.

Early Application of Permanent Metallic Mesh Stent in Substitution for Temporary Polymeric Ureteral Stent Reduces Unnecessary Ureteral Procedures in Patients With Malignant Ureteral Obstruction

OBJECTIVE

To identify risk factors for metal stent failure in patients who received polymeric double J (PDJ) ureteral stents for malignant ureteral obstructions (MUOs) and review our clinical experiences using a ureteral metallic stent.

PATIENTS AND METHODS

Patients who underwent metallic stent placement to replace a double J ureteral stent for nonurological MUO between January 2011 and February 2014 were included. The collected data included gender, age, laterality, cause of obstruction, PDJ ureteral stenting duration, immediate success of the metal stent, and additional procedures to relieve obstruction after metal stenting (eg, additional metal stenting or percutaneous nephrostomy (PCN) indwelling catheter placement). Cox regression tests were used for the statistical analyses.

RESULTS

In this analysis 40 ureteral units were included. There was no initial technical failure. However, 9 (22.5%) units required additional procedures due to de novo ureteral obstruction, including additional indwelling metal stents (7.5%), additional PDJ stenting (10%), or indwelling percutaneous nephrostomy (5%). Univariate and multivariate analyses revealed that the duration of previous PDJ ureteral stenting was an independent prognostic factor for predicting ureteral metal stent failure (hazard ratio = 1.063, 95% confidence interval = 1.004-1.125; P = .037).

CONCLUSION

Long-term indwelling of a PDJ ureteral stent increases the risk of additional management for de novo ureteral stricture after ureteral metal stent replacement for nonurological MUO. Our data suggest that careful patient selection and counseling for those at high risk are needed when metal stent replacement is considered for patients with long-term PDJ ureteral stents for MUO.

Comparison of efficacy and safety between a segmental thermo-expandable metal alloy spiral stent (Memokath 051) and a self-expandable covered metallic stent (UVENTA) in the management of ureteral obstructions

OBJECTIVE

To determine the efficacy and safety of the Memokath 051™ (PNN Medical, Glostrup, Denmark) and UVENTA™ (Taewoong Medical, Seoul, Korea) metal stents, we reviewed our experience with these two metallic ureteral stents for treating benign and malignant ureteral obstructions.

SUBJECTS AND METHODS

Twenty-seven patients who received treatment with metallic ureteral stents (Memokath 051, 10 patients; UVENTA, 17 patients) from November 2011 to May 2013 at our institution were identified and analyzed. We conducted a comparative analysis of the causes of obstruction, technical/clinical success rate, cause of failure, and complications.

RESULTS

No difference was observed between the two metallic stents for the causes of benign and malignant ureteral obstructions (P=.073). The Memokath 051 and the UVENTA were inserted successfully in all ureters using a retrograde technique. The mean follow-up was 13.6 months for Memokath 051 and 12 months for UVENTA (P=.244). The clinical success rate of the UVENTA was higher than that of Memokath 051 (82.4% versus 42.9%; P=.031). The causes of failure were obstruction by tumor progression (n=2) and stent migration (n=6) in cases that received Memokath 051 and stent migration (n=1) and obstruction by mucosal hyperplasia (n=2) in UVENTA. The complications caused by Memokath 051 were intermittent flank pain (n=1) and acute pyelonephritis (n=1), whereas those of UVENTA were intermittent flank pain (n=1), gross hematuria (n=1), and acute pyelonephritis (n=1).

CONCLUSIONS

The UVENTA achieved a higher clinical success rate than the Memokath 051. Our study demonstrated that the UVENTA is safe and effective in the management of benign and malignant ureteral obstruction. The complications were similar between the two metallic stents.