Available via license: CC BY-NC 4.0
Content may be subject to copyright.
Research Article
Urol Int 2022;106:482–486
Allium Ureteral Stent as a Treatment for
Ureteral Stricture: Results and Concerns
Ofir Avitan
a Zaher Bahouth
a Sagi Shprits
a Miguel Gorenberg
b
Sarel Halachmi
a
aDepartment of Urology, Bnai-Zion Medical Center, Haifa, Israel; bDepartment of Nuclear Medicine, Bnai-Zion
Medical Center, Haifa, Israel
Received: December 1, 2021
Accepted: January 20, 2022
Published online: March 1, 2022
Correspondence to:
Ofir Avitan, ofir.avitan @ gmail.com
© 2022 The Author(s)
Published by S. Karger AG, Basel
Karger@karger.com
www.karger.com/uin
DOI: 10.1159/000522174
Keywords
Ureteral stricture · Allium stent · Ureteral stent
Abstract
Introduction: Ureteral strictures could be a chronic illness
that leads to severe side effects and poor quality of life. A
treatment with an Allium ureteral stent (URS), a self-expand-
ing, large-caliber URS, was implemented in our department
for ureteral stricture. Our study aim was to report the long-
term results, including success rate, complications, and ad-
verse effects. Methods: We retrospectively collected data on
all patients who were treated with an Allium URS in our de-
partment between January 2017 and January 2021. Demo-
graphic, clinical, radiological, and perioperative parameters
were retrieved and analyzed. The primary outcome was stric-
ture resolution rates following stent removal. Results: Our
cohort included 17 patients, 9 men and 8 women. The etiol-
ogy of ureteral strictures was urolithiasis in 76.5% and pelvic
procedure injury in 17.6%. The overall success rate was
35.29% in an average follow-up of 10.42 ± 2.39 months after
stent removal. A higher failure rate was observed in the uro-
lithiasis etiology group (90% vs. 66.7%, p = 0.38). The mean
indwelling time of the Allium stent was 14.29 ± 1.29 months.
Conclusions: Although an Allium URS could be considered
as a feasible and attractive treatment of ureteral strictures,
due to its minimal invasiveness, the success rate of this treat-
ment is relatively low. Therefore, this option should be care-
fully considered and should be discouraged in young and fit
patients and reserved for older unfit patients who are unwill-
ing to undergo surgical repair of ureteral strictures.
© 2022 The Author(s)
Published by S. Karger AG, Basel
Introduction
Ureteral strictures can be treated by several approach-
es [1], including placement of ureteral stents (URSs) in
patients unwilling or unfit for definitive treatment. The
standard pigtail URS have many side effects, including
tissue inflammatory reaction, infection, and tube encrus-
tation, leading to frequent replacement [2].
In a previous study [3], we demonstrated the advan-
tages of a self-expanding large-caliber nitinol URS (Alli-
um®; Allium LTD, Caesarea, Israel), including reduced
tissue ingrowth, large caliber, high anti-compression
force, and safe use for up to 2 years without the need for
exchange. The aim of this study was to report the long-
term results of all patients who were treated with the Al-
lium® URS at our department.
is is an Open Access article licensed under the Creative Commons
Attribution-NonCommercial-4.0 International License (CC BY-NC)
(http://www.karger.com/Services/OpenAccessLicense), applicable to
the online version of the article only. Usage and distribution for com-
mercial purposes requires written permission.
Allium Ureteral Stent for Ureteral
Stricture: Results and Concerns
483
Urol Int 2022;106:482–486
DOI: 10.1159/000522174
Methods
Data from our institutional database regarding patients treated
with an Allium URS, from January 2017 to January 2021, were ret-
rospectively collected following institutional review board approv-
al.
Allium URS Stent
The Allium URS was designed for the treatment of ureteral
strictures. It is a self-expanding, large-caliber metal stent. It has a
cover of a biocompatible, biostable polymer to make it a nonper-
meable tube to prevent tissue ingrowth into the lumen and early
encrustation. The Allium URS has a longitudinally flexibility and
radial force to keep the ureter lumen open and has a unique unrav-
eling feature to make its endoscopic removal.
Surgical Technique
Insertion of the Allium URS was performed under general
anesthesia. An antegrade ureterogram was done in patients with
indwelling nephrostomy, and a retrograde ureterogram in pa-
tients without a nephrostomy in order to visualize the stricture
and position the stent properly. After the insertion of a guide
wire, some strictures were dilated using balloon ureteral dilator
inflated to 20 atm (1.72 MPa) according to the manufacturer’s
recommendations. The stent was then inserted (in a retrograde
or antegrade fashion), and its position fluoroscopically con-
firmed.
Removal of URS was scheduled in 12–14 months following
stent insertion. The removal was performed using a semirigid ure-
teroscope under general anesthesia, with an endoscopic grasper
due to its unique unraveling feature.
Follow-Up
Six weeks following Allium URS insertion, diethylenetriamine-
pentaacetic acid renogram was performed. If results of renography
did not show obstruction, baseline ultrasonography was per-
formed, and patients subsequently followed up with renal sonog-
raphy, comparing changes in hydronephrosis.
Six weeks following the removal of Allium URS, a renal sonog-
raphy and a diethylenetriaminepentaacetic acid renogram were
performed. If the results showed no obstruction, patients were ad-
vised for sonographic follow-up and serum creatinine. Stent fail-
ure was defined as persistent hydronephrosis with a demonstrated
obstruction in renography.
Statistical Analysis
Processing and analyzing the data were done using SPSS ver-
sion 20 software (IBM, Armonk, NY, USA). To compare the cat-
egorical variables, we used the χ2 Pearson test. Comparison of in-
dependent variables was done by Student’s t test. The continuous
variables were described by mean and standard error of the mean.
The noncontinuous variables were described as percentages. A p
value below 0.05 was considered statistically significant.
Results
The study cohort included 17 patients, 8 women and 9
men, with a mean age of 57.71 ± 3.24 years. Table1 rep-
resents the ureteral stricture properties and demographic
data of all patients.
NMean ± SEM Range p value
Age, years
Success 6 62.5±2.83 53 73 0.29
Failure 11 55.09±4.68 36 82
Total 17 57.71 ± 3.24 36 82
Success Failure Total p value
Gender, n, (%)
Female 3 (37.5) 5 (62.5) 8 (47.1) 0.86
Male 3 (33.3) 6 (66.7) 9 (52.9)
Total 6 (35.3) 11 (74.7) 17
Stricture cause
Unknown, n0 1 1 (5.9) 0.38
Pelvic procedure, n (%) 2 (66.7) 1 (33.3) 3 (17.6)
Urolithiasis, n (%) 4 (30.8) 9 (69.2) 13 (76.5)
Stricture location, n, (%)
Proximal 3 (33.3) 6 (66.7) 9 (52.9) 0.97
Middle 1 (33.3) 2 (66.7) 3 (17.7)
Distal 2 (40.0) 3 (60.0) 5 (29.4)
Laterality, n, (%)
Left 6 (50) 6 (50) 12 (70.6) 0.049
Right 0 5 (100) 5 (29.4)
Table 1. Patients and ureteral stricture
characteristics
Avitan/Bahouth/Shprits/Gorenberg/
Halachmi
Urol Int 2022;106:482–486
484
DOI: 10.1159/000522174
The etiology of ureteral stricture was as follows: 13 pa-
tients (76.5%) due to urolithiasis cause and 3 (17.6%) due
to pelvic procedure (two gynecological surgery and one
aorto-bifemoral stent insertion). One patient had a stric-
ture of unknown origin.
The vast majority of patients had a previous treatment
for ureteral stricture. About 64.7 were treated with bal-
loon dilatation, 17.6% with endoureterotomy, and only
17.6% were not previously treated.
The mean indwelling time of the Allium stent was
14.29 ± 1.29 months, with the shortest recorded time be-
ing 3 month (removed due to stent migration). This pa-
tient with early stent removal had a patent ureter during
follow-up.
Patients were scheduled for stent removal in 12–14
months following stent insertion. However, 2 patients
were left with their Alium stent because of failure to re-
trieve it.
Regarding complications, 5 patients presented with
occluded stent, and all of them were grouped in the failure
group. Three patients presented with obstruction of the
stent due to urolithiasis and needed stone fragmentation
before stent removal. In 2 cases, we were unable to re-
move the Allium URS safely, and a decision was made to
leave the stent in, and both patients required long-term
nephrostomy tube due to ureteral blockage. Two patients
were diagnosed with a second distal ureteral stricture af-
ter the Allium stent removal.
Patients were divided into two groups according to
the final result. Group 1 included 6 patients who need-
ed no further treatment after the removal of the Allium
URS during follow-up, and group 2 comprised of 11
patients who needed further intervention due to ob-
struction. The average follow-up was 10.42 ± 2.39
months without any difference between groups (p =
0.88).
No significant differences were noted between the
study groups in gender or age. Although the location of
stricture did not impact the success rate, the laterality
of the stricture showed a marginal statistical signifi-
cance (p = 0.049. Although all the successful treatments
were on the left side, the failed cases were divided even-
ly between the right and left sides (54.5% vs. 45.5%, re-
spectively).
Several other parameters were analyzed for potential
association with the success rate as shown in Table2. It
can be clearly noted that the previous treatments and
balloon dilations did not impact the success rate. How-
ever, it is noteworthy that patients who suffered from
ureteral stricture due to urolithiasis cause had higher
failure rate compared to others, although this was not
statistically significant (90% vs. 66.7%, p = 0.38). More-
over, indwelling time did not have a positive impact on
success rate.
Table 2. Allium stent peri-procedure variables
NMean ± SEM Range p value
Follow-up, months
Success 6 9.93 ± 4.13 1.5 26.43 0.88
Failure 11 10.69 ± 3.07 0.43 31.7
Total 17 10.42 ± 2.39 0.43 31.7
Indwelling time of the Allium stent, months
Success 6 14.03 ± 2.57 2.97 20.53 0.87
Failure 9 14.46 ± 1.45 7.77 22.13
Total 15 14.29 ± 1.29 2.97 22.13
Success Failure Total p value
Previous ureteral stricture management, n, (%)
Dilation 3 (27.3) 8 (72.7) 11 (64.7) 0.45
Endoureterotomy 2 (66.7) 1 (33.3) 3 (17.6)
No dilation 1 (33.3) 2 (66.7) 3 (17.6)
Ureteral dilation during Allium stent insertion, n, (%)
Dilation 4 (28.5) 10 (71.5) 14 (82.3) 0.21
No dilation 2 (66.7) 1 (33.3) 3 (17.7)
Total 6 (35.3) 11 (74.7) 17 (100)
Allium Ureteral Stent for Ureteral
Stricture: Results and Concerns
485
Urol Int 2022;106:482–486
DOI: 10.1159/000522174
Discussion
Ureteral stricture should be treated to prevent renal
unit dysfunction. The management of ureteral strictures
could be challenging. The primary treatment is usually
done by insertion of a pigtail stent or nephrostomy tube
followed by a definitive, usually surgical treatment. An-
other option for patients unwilling or unfit for surgical
intervention is a constant indwelling URS or nephrosto-
my tube with periodic exchange. These options could car-
ry a lot of inconvenience for patients.
An Allium URS could offer another treatment option,
and we aimed to report our experience with it. The Alli-
um URS has several advantages over other URSs. Its fea-
tures include a wide-diameter, polymer cover that pre-
vents tissue ingrowth, an ability to anchor in the ureter,
and an increased radial force that allows the lumen to
remain open even in cases of significant external pres-
sure. The first reports of its efficacy were remarkable [3],
and in this study, we reported its real-life efficacy in pa-
tients treated at our department.
The results of our study indicate that the stent can be
easily inserted, regardless of the severity and location of
the stricture, without significant complications. Stent mi-
gration was recorded in only one patient. Five stents were
blocked during follow-up and necessitated early removal.
Three stents were blocked due to ureteral stones, and 2
were blocked due to severe stricture at the distal end of
the Allium stent.
Xiong et al. [4] reported the results of 83 patients who
were diagnosed with a ureteral stricture after ureteroscop-
ic lithotripsy and showed a 60.9% success rate when pa-
tients were treated with ureteral dilatation or endoureter-
otomy. A literature review made by Hafez et al. [5] report-
ed success rates of endoureterotomy from 55% to 85% for
benign ureteral strictures and balloon dilatation success
rates from 48% to 88%, with an overall mean of 55%.
Although our results did not show statistically significant
difference in the success rate between patients who were
treated with ureteral dilatation or endoureterotomy before
stent insertion and patients who did not undergo such treat-
ments, there was a clear trend toward a better outcome of
almost 20%. Hence, ureteral dilatation or endoureterotomy
should be considered prior to Allium URS insertion.
The success rate of surgical ureteral repair, regardless
of the approach (open, laparoscopic, or robot-assisted),
are 90% and above [4]. Seideman et al. [6] reported their
results of 45 patients who underwent laparoscopic ure-
teral reimplantation due to distal ureteral stricture with
an overall success rate of 96%. They defined success as
radiographic evidence of no residual obstruction, symp-
toms, renal deterioration, or need for subsequent proce-
dures. Another study by Soares et al. [7]. reported the
results of 10 patients who underwent laparoscopic ure-
teral reimplantation due to distal and middle ureteral
stricture, with an overall success rate of 100%. Kolontarev
et al. [8] presented a systematic literature review of robot-
assisted laparoscopic (RAL) ureteral reconstruction in-
volving 245 RAL and 76 open ureteral surgery cases and
concluded that the recurrence stricture rates in RAL and
open groups were similar of about 9%.
When endoscopic treatment with balloon dilatation or
endoureterotomy fails or not suitable, a definitive treat-
ment by using the Allium URS becomes very attractive,
due to its endoscopic approach and minimal invasive-
ness. In our study, we reported a success rate of 35% as a
definitive ureteral stricture treatment, which is far lower
than surgical repair. Hence, the decision should be care-
fully discussed with patients before opting for the Allium
URS. On one hand, a trial with Allium URS could poten-
tially treat ureteral stricture and avoid surgical procedure;
on the other hand, failure of the Allium URS could cause
a blocked ureter or a second stricture (18%) that could
increase the complexity of the following surgical proce-
dures.
This study has several limitations that are mainly due
to the small number of patients. However, the low long-
term success rate of the Allium URS should encourage
patients and urologists to avoid this option in younger
patients and keep it as an option to be considered for spe-
cific unfit patients who could potentially benefit from it.
Conclusions
Although an Allium URS could be considered as a fea-
sible and attractive treatment of ureteral strictures due to
its minimal invasiveness, the success rate of this treat-
ment is relatively low. In our opinion, it may be used in
selected cases as a permanent stent but not as a tool of
definitive treatment.
Statement of Ethics
The Ethics Committee of the Bnai-zion medical center ap-
proved this study (REC number: 0049-10-BNZ). The present study
was carried out retrospectively, and the need to obtain written in-
formed consent from the patients was waived by the Institutional
Review Board. Personal identifiers of the patients were removed,
and the data were analyzed anonymously.
Avitan/Bahouth/Shprits/Gorenberg/
Halachmi
Urol Int 2022;106:482–486
486
DOI: 10.1159/000522174
Conflict of Interest Statement
The authors have no conflicts of interest to declare.
Funding Sources
The authors received no financial support for the research, au-
thorship, and/or publication of this article.
Author Contributions
O.A. and Z.B.: carried out the data collection and statistics anal-
ysis and wrote the paper; M.G.: participated in the design of the
study; S.S.: collected the data; S.H.: conceived the study and par-
ticipated in its design and coordination and helped to draft the
manuscript. All authors read and approved the final manuscript.
Data Availability Statement
The data that support the findings of this study are not pub-
licly available due to the containing information that could com-
promise the privacy of research participants but are available from
the corresponding author O.A. upon reasonable request.
References
1 Meretyk S, Albala DM, Clayman RV, Denst-
edt JD, Kavoussi LR. Endoureterotomy for
treatment of ureteral strictures. J Urol. 1992;
147(6): 1502–6.
2 Al-Aown A, Kyriazis I, Kallidonis P, Kraniotis
P, Rigopoulos C, Karnabatidis D, et al. Ure-
teral stents: new ideas, new designs. Ther Adv
Urol. 2010; 2(2): 85–92.
3 Moskovitz B, Halachmi S, Nativ O. A new
self-expanding, large-caliber ureteral stent:
results of a multicenter experience. J Endou-
rol. 2012; 26(11): 1523–7.
4 Xiong M, Zhu X, Chen D, Hossain MA, Xie Y,
Gou X, et al. Post ureteroscopic stone surgery
ureteral strictures management: a Retrospec-
tive Study. Int Urol Nephrol. 2020; 52(5): 841–
9.
5 Hafez KS, Wolf JS Jr. Update on minimally
invasive management of ureteral strictures. J
Endourol. 2003; 17(7): 453–64.
6 Seideman CA, Huckabay C, Smith KD, Perm-
pongkosol S, Nadjafi-Semnani M, Lee BR, et
al. Laparoscopic ureteral reimplantation:
technique and outcomes. J Urol. 2009; 181(4):
1742–6.
7 Soares RS, de Abreu RA Jr, Tavora JE. Lapa-
roscopic ureteral reimplant for ureteral stric-
ture. Int Braz J Urol. 2010; 36(1): 38–43.
8 Kolontarev K, Kasyan G, Pushkar D. Robot-
assisted laparoscopic ureteral reconstruction:
а systematic review of literature. Cent Euro-
pean J Urol. 2018; 71(2): 221–7.
