Ileal ureter replacement for patients with long ureteral strictures after Allium stent failure: the initial experience

Abstract

Purpose

To present the initial experience and clinical outcomes of ileal ureteric replacement (IUR) for complex ureteral stricture after treatment failure of Allium stents.

Methods

From June 2020 to July 2022, a total of eight patients underwent IUR for complex ureteral strictures after treatment failure of Allium stents across three tertiary centers. Surgical approaches included open (n = 3), laparoscopic (n = 2), and robot-assisted (n = 3). The clinical data and follow-up results were prospectively collected.

Results

A total of eight patients were enrolled, including seven women and one man, with a mean age of 47.8 years. The median dwelling time of Allium stents was 12.5 months. Reasons for Allium stent failure included recurrent urinary tract infection (UTI), stent migration, unrelieved hydronephrosis and stent calculus. The median stricture length was 15 cm. Four patients underwent unilateral IUR and four underwent bilateral IUR, with a median harvested ileal segment length of 25 cm. The median operation time was 261 min and the median estimated blood loss was 75mL. During a median follow-up of 24 months, ureteral patency was achieved in all patients. The mean eGFR was 71.2 ± 34.5 preoperatively and 65.9 ± 23.9 mL/min/1.73m² at the last follow-up (p = 0.394). Two patients in the open surgery group experienced major complications, specifically ileus and incisional hernia. Long-term minor complications included UTI (n = 5) and metabolic acidosis (n = 2).

Conclusion

Allium stents should be applied with caution and strict indications. For patients experiencing stent failure, IUR serves as a viable salvage option for managing long and complex ureteral strictures.

Introduction

Ureteral stricture is defined as a fixed narrowing of the ureter, leading to functional obstruction and subsequent hydronephrosis of the affected kidney [1, 2]. This condition can cause flank pain, nausea, urinary tract infections, hematuria, and calculus formation, potentially progressing to irreversible kidney failure if not treated promptly [3, 4]. Consequently, timely intervention to relieve the obstruction is crucial for the patient’s long-term prognosis. Currently, surgical reconstruction to reestablish stable urinary flow is the primary treatment method [3]. Ureteral stents are often employed as a temporary measure to alleviate obstruction or as an adjunct to reconstructive surgery [5].

The Allium stent is a novel self-expanding ureteral metal stent coated with a biocompatible material to prevent tissue ingrowth into the lumen and early encrustation [6]. Compared to traditional ureteral stents, the Allium stent is designed for prolonged indwelling, reducing the need for frequent replacement [7]. Moskovitz et al. [6] first reported the results of the Allium stent evaluation, considering it a safe and effective treatment for long-term maintenance of ureteral patency. Despite its innovative design, the Allium stent has been associated with several complications in practice, including stent migration, blockage, urinary tract infection, and unresolved hydronephrosis. Failure of Allium stents may lead to additional ureteral damage, which increases the complexity of subsequent surgery [2, 8]. The optimal treatment approach for patients following Allium stent failure remains uncertain.

Ileal ureter replacement(IUR) has been demonstrated to be a safe and reliable treatment for long ureteral stricture, even in complex conditions [9], potentially offering an option for treating complex ureteral lesions following Allium stent failure. This study aimed to summarize the characteristics of patients with long ureteral obstruction after Allium stent failure, and report the experiences with IUR in treating these patients.

Materials and methods

Study population

Eight patients who underwent IUR after Allium stent failure at three centers between June 2020 and July 2022 were included. Indications for surgery included long or multiple ureteral strictures, persistent symptoms, impaired renal function, and radiographically demonstrated obstruction. The preoperative glomerular filtration rate (GFR) needed to be ≥10 ml/min or the urine volume per day had to exceed 400 ml for the affected kidney. All operations were performed by an experienced surgeon. The clinical data and follow-up outcomes were prospectively collected in our Reconstruction of Urinary Tract: Technology, Epidemiology and Result (RECUTTER) database.

Preoperative preparation

The Allium stent was removed preoperatively in all but one patient, where the stent was difficult to remove and thus removed intraoperatively (Fig. 1). Furthermore, one patient discovered multiple ureteral polyps while removing the Allium stent. All patients received nephrostomy at least two months before surgery to allow the ureter to rest adequately. Preoperative intravenous urography (IVU) or retrograde urography (RGU) was performed to assess the location and length of the ureteral stricture (Fig. 2A-B). Renal function was evaluated using GFR and diuretic renography. Three-dimensional (3D) images based on computed tomography urography (CTU) were used to guide preoperative surgical planning and intraoperative navigation (Fig. 2C-D).

Fig. 1.

Intraoperative removal of the Allium stent. (A) The Allium stent was removed from an incision in the ureter. The dotted yellow lines show the outline of the ureter. The dotted blue lines show the outline of the Allium stent. (B) The Allium stent was successfully removed

Fig. 2.

Preoperative urography and three-dimensional reconstruction of four different patients. (A) Preoperative urography before the removal of the Allium stent. The yellow area indicates the Allium stent. (B) Preoperative urography after the removal of the Allium stent. (C) Preoperative three-dimensional reconstruction before the removal of the Allium stent. The yellow area indicates the Allium stent. (D) Preoperative three-dimensional reconstruction after the removal of the Allium stent

Surgical technique

Our surgical techniques, encompassing open, laparoscopic, and robotic surgery, have been detailed in previous articles [10–12]. The main surgical steps were as follows: First, the diseased ureter was fully exposed. Notably, tissue adhesion and degeneration around the ureter in these patients were severe, necessitating delicate dissection. The ureter itself was scarred and rigid, requiring careful identification and complete removal of the inactive section. In one patient, the Allium stent remaining in the ureter was carefully removed. The length of the ureteral lesion was re-measured using a calibrated ureteral catheter. After incision of the ureter proximal to the stricture segment, the required ileum segment was obtained approximately 20 cm from the ileocecal valve. The intestinal continuity was restored via side to side anastomosis. The proximal end of the ileal ureter was anastomosed with the ureteral stump or the pelvic end. In bilateral IUR, one side was anastomosed end-to-end and the other side end-to-side, appearing 7-shaped or reverse-7-shaped. The ileal ureter was placed isoperistaltically, and its distal end was anastomosed to the bladder.

Postoperative management and follow-up

Single-J or double-J stents were removed 2 months postoperatively. Nephrostomy tubes were clamped 1–2 weeks after surgery. One week following stent removal, a video urodynamics examination was performed to confirm ureteral patency, after which the nephrostomy tube was removed. To evaluate the morphology and peristalsis of the reconstructed upper urinary tract, cine magnetic resonance urography (MRU) was performed 3 months postoperatively. At 6 months after surgery, patients underwent computed tomography urography (CTU), ultrasonography, and diuretic renal dynamic imaging. Thereafter, follow-up was conducted every 6 months, primarily utilizing CTU and ultrasonography, with renal dynamic imaging recommended as needed. Laboratory examinations performed at each visit included complete blood count, serum creatinine, estimated glomerular filtration rate (eGFR), blood gas analysis, urinalysis, and urine culture. Postoperative complications were graded according to the Clavien-Dindo (CD) grading system. We defined grades I and II as minor complications and grades III or higher as major complications. Technical success was defined as ureteral patency, characterized by no indwelling stents or tubes, no radiographic obstruction, and no obstructive symptoms. Late-term renal function decline was defined as a decrease in eGFR exceeding 10% at the last follow-up (>1 year postoperatively) compared to the level measured at 6 months postoperatively.

Statistical analysis

Continuous variables with normal distribution were expressed as mean ± standard deviation (SD), while non-normally distributed variables were reported as median. Paired continuous variables satisfying normality assumptions were compared using the paired t-test, and 95% confidence intervals (CIs) were reported. A two-tailed p-value < 0.05 was considered statistically significant. All analyses were conducted using SPSS version 29.0.

Results

The characteristics of eight patients are summarized in Table 1, including seven women and one man, with a mean age of 47.8 ± 11.4 years. The mean body mass index (BMI) was 23.61 ± 3.14 kg/m². Six patients had bilateral involvement, while two had unilateral involvement. Of the bilateral cases, one underwent concurrent contralateral nephrectomy for a non-functioning kidney, while another required no contralateral surgical intervention due to mild hydronephrosis. Consequently, a total of 12 ureteral units required intervention. Strictures involved the mid-distal ureter (n = 6), the distal ureter (n = 2), and the entire ureter (n = 4), with a median length of 15 cm (range: 10–20 cm). The etiologies of the ureteral strictures prior to treatment with Allium stents included cervical cancer surgery and radiotherapy (62.5%), failed pyeloplasty for UPJO (12.5%), lithotripsy (12.5%), and malakoplakia (12.5%). The median dwelling time of Allium stents was 12.5 months (range: 1-24months). Reasons for stent removal included recurrent urinary tract infection (UTI; 50%), stent migration (37.5%), persistent hydronephrosis (37.5%) and stent calculus (25%), with some patients experiencing multiple complications simultaneously. Preoperative symptoms were present in seven patients, including flank pain (75%) and UTI (50%), and only one patient was asymptomatic.

Table 1.

Patient characteristics and preoperative findings

Result
Total number of patients, n	8
Gender, n (%)
Male	1(12.5)
Female	7(87.5)
Age (yr), mean ± SD (range)	47.8 ± 11.4 (24–61)
BMI (kg/m2), mean ± SD (range)	23.61 ± 3.14 (19.59–28.13)
Affected side, n (%)
Left	1(12.5)
Right	1(12.5)
Bilateral	6(75.0)
Length of stricture (cm), mean (range, median, IQR)	15.5(10–20, 15, 9.2)
Etiology associated with ureteral stricture before Allium stent placement, n (%)
Cervical cancer surgery + radiotherapy	5(62.5)
Failed pyeloplasty for UPJO	1(12.5)
Lithotripsy	1(12.5)
Malakoplakia	1(12.5)
Reasons for Allium stent failure, n (%)
Recurrent UTI	4(50.0)
Stent migration	3(37.5)
Persistent hydronephrosis	3(37.5)
Stent calculus	2(25.0)
Dwelling time of Allium stent (mo), mean (range, median, IQR)	12.7(1–24, 12.5, 16.2)
Preoperative symptom, n (%)
Flank pain	6(75.0)
UTI	4(50.0)
Asymptomatic	1(12.5)
Preoperative eGFR (mL/min/1.73 m2), mean ± SD (range)	71.2 ± 34.5(36.7-136.6)

BMI body mass index, UPJO ureteral pelvic junction obstruction, UTI urinary tract infection, eGFR estimated glomerular filtration rate

Perioperative details and follow-up results are shown in Table 2. Four patients underwent unilateral IUR and four underwent bilateral IUR. Surgical approaches included open (n = 3), laparoscopic (n = 2), and robotic (n = 3) techniques. The laparoscopic and robotic cases were defined as the minimally invasive group. The median length of the ileum used was 25 cm (range: 15–45 cm). The median operation time was 261min (range: 215–445min). The median estimated blood loss was 75mL (range: 20-600mL), and the median postoperative hospitalization was 15.5 days (range: 7-35days). Regarding the surgical approach, operative times in the robotic group (215, 230, and 252 min) appeared shorter than the median time of the non-robotic group (285 min). All patients in the minimally invasive group had an estimated blood loss of ≤100 mL. In the open surgery group, two patients had a blood loss of 600 mL, with one requiring intraoperative transfusion. Postoperative complications during hospitalization included ileus (CD grade I) in three cases (37.5%) and UTI (CD grade Ⅱ) in two case (25.0%), all managed conservatively.

Table 2.

Perioperative details and follow-up results

Result
Surgical procedure, n (%)
Unilateral IUR	4(50.0)
Left	1(12.5)
Right	3(37.5)
Bilateral IUR	4(50.0)
Surgical approach, n (%)
Open	3(37.5)
Laparoscope	2(25.0)
Robot-assisted	3(37.5)
Length of harvested ileal segment (cm), mean (range, median, IQR)	24.8(15–45, 25, 13)
Operative time (min), mean (range, median, IQR)	282.8(215–445, 261, 72)
Estimated blood loss (mL), mean (range, median, IQR)	193.8(20–600, 75, 440)
Intraoperative complications, n (%)
Transfusion	1(12.5)
Postoperative hospitalization (d), mean (range, median, IQR)	16(7–35, 15.5, 6.8)
Postoperative complications, CD grade, n (%)
Ileus (grade I)	3(37.5)
UTI (grade Ⅱ)	2(25.0)
Follow-up time (mo), median (range)	24(19–40)
Postoperative eGFR (ml/min/1.73 m2), mean ± SD (range)
Postoperative 6 ± 2mo	64.4 ± 27.4(27.0-118.6)
Last follow-up (15-36mo)	65.9 ± 23.9(32.9-108.4)
Long-term complications, CD grade, n (%)
Metabolic acidosis (grade I)	2(25.0)
UTI (grade Ⅱ)	5(62.5)
Surgical treatment of ileus (grade IIIb)	1(12.5)
Surgical treatment of incisional hernia  (grade IIIb)	1(12.5)
Technical success	8/8

CD Clavien-Dindo, IQR interquartile range, UTI urinary tract infection

The median follow-up duration was 24 months (range: 19-40months). Imaging revealed no obstructions in all patients. Two patients who underwent open surgery required surgical interventions during follow-up for ileus (CD grade IIIb) and incisional hernia (CD grade IIIb), respectively. No major complications occurred in the minimally invasive group. Long-term complications also included UTI (CD grade Ⅱ) in five cases (62.5%) and metabolic acidosis (CD grade I) in two cases (25%). The mean preoperative eGFR was 71.2 ± 34.5 mL/min/1.73 m². At 6 months postoperatively, the mean eGFR was 64.4 ± 27.4 mL/min/1.73 m², showing no statistically significant difference from preoperative levels (95% CI: -18.0 to 4.6; p = 0.203). The latest mean eGFR was 65.9 ± 23.9 mL/min/1.73 m², which did not differ significantly from either the preoperative baseline (95% CI: -18.9 to 8.4; p = 0.394) or the 6-month postoperative levels (95% CI: -9.1 to 12.0; p = 0.753). One patient experienced late-term renal function decline. At the latest follow-up, technical success was achieved in all patients.

Discussion

In patients with ureteral stricture, urine drainage is essential to maintain or restore kidney function.

Patients with acute ureteral obstruction is typically alleviated through percutaneous nephrostomy or ureteral stents [13]. For persistent and irreversible ureteral defects, surgical reconstruction is recommended. The strategy for ureteral reconstruction depends on the length and location of the ureteral stricture. Short segment ureteral strictures can be treated by ureterocystostomy, uretero-ureterostomy, pyeloplasty, or oral mucosal graft ureteroplasty. For long, multiple complex ureteral strictures, IUR may be the last resort [14, 15]. Nephrostomy and ureteral stents often serve as alternative treatments, particularly for patients with primary malignant disease, high surgical complexity, or those unwilling to undergo surgery [16, 17].

The Allium stent, a new type of metal stent, is frequently employed in the long-term non-surgical management of ureteral obstruction. It is primarily used for malignant obstruction. It has also been reported in cases of refractory benign obstruction caused by radiotherapy, kidney transplantation, ureteroscopic injury, or retroperitoneal fibrosis [8, 18, 19]. However, complications associated with Allium stents are common, often resulting in treatment failure and early removal. Reported success rates vary widely across studies, ranging from 35% to 95%. The failure of Allium stents is common and the main causes are obstruction, migration and UTI [2, 6–8, 18–23]. Avitan et al. [2] reported an obstruction rate of 59% in 10 cases of obstruction following Allium stent placement. In two of these cases, severe ureteral stricture developed distal to the Allium stent. Salciccia et al. [24] reported a case of severe hydronephrosis with subsequent loss of renal function due to the development of ureteral achalasia, potentially related to inflammation and fibrosis caused by the Allium stent.

In our study, eight patients had significant ureter defects prior to Allium stent placement, which may explain why surgical reconstruction was initially not chosen. During the removal of the Allium stent in one patient, multiple polyps were discovered in the ureter. In another patient, the removal of the Allium stent before surgery failed. Serious tissue adhesion was observed during the operation, which may be related to previous radiotherapy, surgical history and Allium stent placement. Combining previous reports with our results, we identified several shortcomings of the Allium stent. The success rate of the Allium stent remains controversial, necessitating high-quality clinical trials to clarify its indications and effectiveness. Despite the biocompatible coating, the Allium stent may provoke an inflammatory response in the ureter, leading to tissue growth and adhesion. In severe cases, this can result in multiple ureteral polyps or ureteral achalasia. These complications can impair urine drainage and shorten the stent’s lifespan, thereby reducing patients’ quality of life and imposing a financial burden. Therefore, the risks associated with the Allium stent must be thoroughly evaluated prior to its application. When failure occurs, surgical reconstruction via IUR serves as a viable salvage option.

Technical success was achieved in all patients in our cohort despite the presence of severe ureteral lesions with strictures exceeding 10 cm and complex intraoperative conditions. Evaluation of renal function revealed a slight numerical decline in the early postoperative period that was not statistically significant. This was followed by long-term stability. However, the limited statistical power inherent to our small sample size mandates a cautious interpretation of these data. One patient experienced late-term functional decline without progression to renal failure. It is worth noting that postoperative complications were not uncommon. The incorporation of bowel segments into the urinary tract carries inherent risks [9]. These include bowel-related complications, an increased probability of UTI, and long-term metabolic acidosis.

Therefore, technical patency is merely the foundation of clinical success. Long-term surveillance is mandatory to manage postoperative complications and detect insidious functional decline, even in the absence of stricture recurrence. The open surgery group was associated with higher blood loss and two major complications, including ileus and incisional hernia. The robotic group demonstrated relatively shorter operative times. While purely descriptive, these findings reflect the trend of minimally invasive techniques in optimizing IUR. In particular, robotic technology holds promise for reducing intraoperative trauma and improving prognosis due to its high-definition 3D visualization and superior dexterity. This aligns with our previous reports on totally intracorporeal robotic techniques [12]. Overall, our preliminary experience indicates that IUR represents a feasible salvage option for relieving obstruction and preserving renal function in patients facing long and complex ureteral strictures following Allium stent failure.

We recommend personalized treatment for patients with ureteral stricture. Indwelling metal stents, such as the Allium stent, are suitable for patients with poor baseline health, active tumors, or short life expectancy. Hu H et al. reported satisfactory results with the Allium stent in patients with malignant ureteral stricture, noting improved quality of life [19]. For patients with good baseline health, no current tumors, and long life expectancy, surgical reconstruction yields favorable outcomes [2, 25, 26].

Our study has some limitations. First, given the rarity of patients requiring IUR after Allium stent failure, a formal sample size calculation was not feasible. The resulting small cohort of eight patients inherently limits statistical power. Therefore, our results should be considered descriptive and preliminary. Second, although data were retrieved from a prospectively maintained database, the study remains retrospective and lacks a concurrent control group managed with alternative strategies like autologous kidney transplantation or long-term nephrostomy. Third, the cohort comprises a highly selected group of patients fit for major reconstructive surgery. This selection bias limits the generalizability of our findings to the broader population of patients. Finally, while the median follow-up was 24 months, an extended observation period is necessary to fully characterize late-term outcomes. Further research is needed to refine patient selection criteria and to assess the long-term durability of IUR as a salvage modality in this specific clinical setting.

Conclusion

Allium stents should be applied with caution and strict indications. For patients experiencing stent failure, IUR serves as a viable salvage option for managing long and complex ureteral strictures.

Abbreviations

3D

Three-dimensional

BMI

Body mass index

CD

Clavien-Dindo

CI

Confidence interval

CTU

Computed tomography urography

eGFR

Estimated glomerular filtration rate

IQR

Interquartile range

IUR

Ileal ureter replacement

IVU

Intravenous urography

MRU

Magnetic resonance urography

RECUTTER

Reconstruction of urinary tract: technology, epidemiology and result

RGU

Retrograde urography

SD

Standard deviation

UPJO

Ureteropelvic junction obstruction

UTI

Urinary tract infection

Authors’ contributions

Project development: KL Yang, XS Li; Data collection: GP Han, ZH Li, X Wang, YM Zhang, ZH Tao, XF Li, HJ Zhu; Data analysis: YM Zhang, X Wang, ZH Li; Project administration: YM Zhang, ZH Li, P Zhang, B Wang; Manuscript writing: YM Zhang, X Wang; Supervision: KL Yang, K Zhang, LQ Zhou, XS Li.

Funding

The authors did not receive support from any organization for the submitted work.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study was approved by the Ethics Committee of Peking University First Hospital. All methods were performed in accordance with the Declaration of Helsinki. All patients have signed written informed consent.

Consent for publication

Written informed consent was obtained from all individual participants included in the study for the publication of their clinical data and accompanying images.

Competing interests

The authors declare no competing interests.