Abstract
Background/Aim: Malignant ureteral obstruction is associated with high rates of failure with traditional ureteral stents. Double-J metallic mesh ureteral stent is one of the latest options for treating malignant ureteral obstruction. However, data regarding the efficacy of using this stent in this context are limited. Thus, we retrospectively investigated the efficacy of this stent. Patients and Methods: We retrospectively analyzed the records of all patients who required double-J metallic mesh ureteral stent placement for malignant ureteral obstruction at Ishikawa Prefectural Central Hospital (Kanazawa, Japan) between October 2018 and April 2022. Primary stent patency was defined as complete or partial resolution of hydronephrosis as shown by imaging studies or successful removal of a preexisting nephrostomy tube. Stent failure was defined as unplanned stent exchange or nephrostomy tube placement for signs or symptoms of recurrent ureteral obstruction. A competing risk model was used to estimate the cumulative incidence of stent failure. Results: Double-J metallic mesh ureteral stents were placed in 63 ureters of 44 patients (13 males, 31 females). The median age of patients was 67 years (range=37-92 years). There was no grade 3 or higher complications. The overall primary patency rate was 95% (60 ureters). Stent failure occurred in seven patients (11%) during follow-up. The cumulative incidence of stent failure at 12 months after placement was 17.3%. Conclusion: Double-J metallic mesh ureteral stent is a safe, simple, and promising treatment option for malignant ureteral obstruction.
Malignant ureteral obstruction (MUO) can be caused by a malignancy that compresses the ureter externally. This obstruction can be relieved by using internal drainage with ureteral stents or external drainage with percutaneous nephrostomy. However, nephrostomy tends to deteriorate patient’s quality of life because of the external drainage tube and its risk of dislodgment. Therefore, ureteral stents are usually considered as the first treatment choice. Despite their advantages, conventional double-J polymeric ureteral stents have demonstrated relatively high failure rates in the management of MUO, and these stents must be replaced every 3 months (1, 2).
Metallic ureteral stent is one of the latest options for managing MUO. Metallic stents are highly resistant to extrinsic compression and have a longer indwelling time compared with polymeric ureteral stents (3). The currently available double-J metallic ureteral stents utilize a metal coil either as the stent itself (Resonance®, Cook Medical, Bloomington, IN, USA) or embedded within the stent wall (4). The Resonance® stent is a tightly coiled wire made of nickel–cobalt–chromium–molybdenum alloy. The positioning of this stent is the same as those of conventional stents, with the upper end placed in the renal pelvis and the lower end in the urinary bladder. This stent is highly resistant to external compressive forces and is at least three to four times more robust than conventional polymeric stents (5, 6). Although previous studies have reported that the Resonance® stent has high patency, it has no central lumen and requires some familiarity with stent placement. The Tumor DD Ureter Stent (Rüsch, Teleflex Medical) is one of the latter type of metallic ureteral stents. It is a hydrophilic coated ureteral stent made of polymeric tubing reinforced with stainless mesh. This stent has a lumen and can be implanted in the same manner as conventional double-J polymeric ureteral stents.
Although benchtop studies of double-J metallic mesh ureteral stents have been performed, there is a lack of evidence regarding their clinical performance (4). Thus, we conducted the present study to evaluate the efficacy of this stent for patients with MUO.
Patients and Methods
The records of 44 patients who underwent metallic ureteral stent placement for MUO at Ishikawa Prefectural Central Hospital (Kanazawa, Japan) between October 2018 and April 2022 were retrospectively analyzed. Bilateral ureters in the same patient were counted as separate ureteral units. The collected medical data included age, sex, Eastern Cooperative Oncology Group Performance Status, primary cancer site, laboratory data, degree of hydronephrosis, laterality, stenotic portion, existence of previous polymeric ureteral stent, and treatment for cancer after metallic ureteral stent placement. According to the Society for Fetal Urology hydronephrosis grading system, the degree of hydronephrosis (grades 0-4) was classified based on renal ultrasonography or computed tomography (7). The stenotic portion was defined as upper, middle, or lower ureter according to the location above, over, or below the sacroiliac joint, respectively. In case a polymeric ureteral stent had been implanted preoperatively, we also evaluated whether stent failure with polymeric ureteral stent had occurred. All stents placed were double-J metallic mesh ureteral stents (7 Fr, Tumor DD Ureter Stent). This structure has high resistance to collapse caused by compression. The ureteral stent and pusher are connected by a coupling structure, which provides excellent insertion property. The connection is released by pulling out the guidewire and twisting the pusher. Metallic ureteral stents were placed in a standard retrograde fashion by using X-ray guidance in all patients. The length of the metallic ureteral stent was determined by the attending physician. The follow-up interval of imaging or blood sampling after placement was also determined at the discretion of the attending physician. All complications were defined according to the Clavien-Dindo classification of surgical complications (8).
The primary outcome was the primary patency rate of ureteral stents. Primary patency was defined as a complete resolution or downgrading of hydronephrosis shown by imaging studies or successful removal of a preexisting nephrostomy tube (9). The secondary outcome was stent failure, which was defined as unanticipated stent exchange or nephrostomy tube placement for signs or symptoms of recurrent ureteral obstruction [recurrent hydroureteronephrosis or increasing serum creatinine (sCr)] (10).
The numerical data were subjected to statistical analyses using R version 4.2.0 (The R Foundation for Statistical Computing, Vienna, Austria). The Wilcoxon rank sum test was used to compare the quantitative data between groups.
Because the occurrence of stent failure was the event of interest, we used a competing risk model to calculate the cumulative incidence of stent failure. Considering death without stent failure as a competing event, the cumulative incidence of stent failure was estimated by the nonparametric cumulative incidence function. A metallic ureteral stent was replaced regularly in some patients. In case the first replacement was performed without stent failure, the patient was censored at that time.
Overall survival was defined as the time from metallic ureteral stent placement to final follow-up or death and calculated using the Kaplan-Meier method. The statistical significance in all analyses was set at p<0.05.
This study was approved by the local research ethics committee at Ishikawa Prefectural Central Hospital (approval number 1991) and conducted in accordance with the Declaration of Helsinki.
Results
A total of 63 stents were inserted into 44 patients (31 females, 13 males) because 19 patients had bilateral stents. The clinical characteristics of the 44 patients are summarized in Table I. The median age of patients was 67 years (range=37-92 years). Gastrointestinal cancer was the most frequent type of malignancy (20 patients, 45.5%), followed by gynecological cancer (13 patients, 29.5%).
Patient characteristics.
Table II shows the patients’ characteristics for each ureter. The most common stenotic portion was upper (37 ureters, 58.7%). Metallic ureteral stents were placed as conversion from conventional polymeric stents (45 ureters, 71.4%) or as the initial intervention for MUO (18 ureters, 28.6%). Most of the polymeric stents implanted previously were 6 Fr in diameter (41 ureters, 91.1%). Among the 45 ureters that had conventional polymeric stents implanted, 20 (44.4%) had stent failure with these stents; therefore, the metallic ureteral stent was replaced as salvage intervention.
Patients’ characteristics for each ureter.
The median sCr level before stenting was 1.0 mg/dl (range=0.5-4.7 mg/dl), which decreased to 0.86 mg/dl (range=0.51-2.1 mg/dl) within a week after stenting (p=0.003). The median grade of hydronephrosis before stenting was 3 (range=0-4), which decreased to 0 (range=0-2) within 3 months after stenting (p<0.001) (Figure 1).
Serum creatinine and hydronephrosis grade before and after the insertion of the double-J metallic mesh ureteral stent.
Among the 63 ureters, primary stent patency was achieved in 60 ureters (95.2%). Imaging studies were not performed for three ureters (4.8%) after stenting because of their short life expectancy; therefore, their primary stent patency was unknown.
Stent failure occurred in seven ureters (11.1%): one ureter developed pyelonephritis, two ureters had stent obstruction, two ureters had worsening hydronephrosis, and one ureter required metallic ureteral stent removal because of bladder irritation symptoms. Among the seven ureters, four ureters were treated by metallic stent exchange, and three ureters had metallic stents replaced by polymeric stents. The cumulative incidence of stent failure at 3, 6, 9, and 12 months after the procedure was 7.3% [95% confidence interval (CI)=2.3%-16.2%], 10.4% (95%CI=3.7%-21.3%), 13.6% (95%CI=5.3%-25.8%), and 17.3% (95%CI=7.3%-30.9%), respectively (Figure 2).
Cumulative incidence curve of stent failure.
In total, twenty-six patients continued treatment for cancer after stent placement, 3 patients were only followed up, and 14 patients were not treated due to disease progression. The treatment details after stenting were not available for one patient.
The median observation period was 100 days (range=1-1,060 days), and the median overall survival time was 155 days (Figure 3). No grade 3 or higher complications occurred during or after metallic ureteral stent placement.
Kaplan-Meier analyses of the overall survival after double-J metallic mesh ureteral stent placement.
Discussion
The management of MUO is difficult for urologists. Polymeric double-J stents or nephrostomies have been the most common treatment for MUO. While ureteral stents are less invasive for patients, they are more likely to cause stent failure. A previous research on polymeric ureteral stents for patients with MUO found a high stent failure rate of 42% (11). On the other hand, nephrostomy tends to deteriorate patient’s quality of life because of the external drainage tube and its risk of dislodgment. In addition, polymeric ureteral stents and nephrostomy tubes must be replaced frequently, which is associated with patient discomfort and reduced quality of life. Thus, metallic ureteral stents were developed to treat patients with MUO.
The Resonance® stent, which is a spiral-shaped, full-length metal stent with the same shape as the double-J catheter, is a commonly used metallic ureteral stent, and many studies have reported its effectiveness (3, 12-20). Previous studies showed that the primary patency rate of the Resonance® stent in patients with MUO was between 87.9% and 96% (9, 13, 15). Moreover, previous studies reported that the 1-year patency rates of the Resonance® stent ranged from 60% to 91.7% in patients with MUO and that the cumulative incidence of stent obstruction at 12 months after stent placement was 18.8% (95%CI=6.1%-29.7%) (3, 14, 21). The present study revealed that double-J metallic mesh ureteral stents had a good primary patency rate of 95.2% for MUO. The incidence of stent failure was 11.1%, and the cumulative incidence of stent failure at 12 months after placement was 17.3% (95%CI=7.3%-30.9%). These results were comparable to those of the Resonance® stent. The double-J metallic mesh ureteral stent may be more useful than the Resonance® stent because it has a lumen through which a guidewire passes, allowing it to be implanted and replaced in the same manner as a conventional polymeric ureteral stent. The Resonance® stent has an anticipated indwelling period of 1 year (15). Although the optimal indwelling period for the double-J metallic mesh ureteral stent was unclear, 1 year seems reasonable given that the results were comparable to those of the Resonance® stent.
MUO has been reported to be an indicator of poor prognosis, with median life expectancy being less than 1 year (22, 23). In the present study, the median survival time after stent placement was 155 days, which was short compared with those of previous studies (14, 15, 24). The median survival time may have been shorter in this study because relatively many patients had metallic stents implanted after the disease progressed and treatment was discontinued. Considering that the median survival of patients with MUO is less than one year, early implantation of metallic stents should be performed to avoid the pain associated with stent replacement. Metallic stents can even be used permanently for patients with shorter life expectancy.
This study has several limitations. First, this is a retrospective study with its intrinsic bias. Second, the patients included in this study did not have a strict standardized follow-up protocol. The follow-up intervals of imaging or blood sampling after metallic stent placement were determined at the discretion of the attending physician. Moreover, the timing of metallic stent replacement was determined at the discretion of the attending physician.
In summary, the double-J metallic mesh ureteral stent is safe and effective for treating MUO. This ureteral stent is a new treatment option for patients with MUO.
Acknowledgements
The Authors would like to thank Enago (www.enago.com) for the English language review.
Footnotes
Authors’ Contributions
Tomohiro Hori: Conceptualization; Date curation; Investigation; Methodology; writing – original draft. Tomoyuki Makino: Supervision; writing – review and editing. Tetsuya Kawahara: writing – review and editing. Satoko Urata: writing – review and editing. Tohru Miyagi: Supervision; writing – review and editing.
Conflicts of Interest
The Authors declare no conflicts of interest in relation to this study.
- Received December 15, 2022.
- Revision received December 25, 2022.
- Accepted December 27, 2022.
- Copyright © 2023 The Author(s). Published by the International Institute of Anticancer Research.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY-NC-ND) 4.0 international license (https://creativecommons.org/licenses/by-nc-nd/4.0).
References
In this issue
Jump to section
Related Articles
Cited By...
- No citing articles found.