Stesura Seveso


237Archivio Italiano di Urologia e Andrologia 2019; 91, 4

ORIGINAL PAPER

Does duration of stenting increase the risk 
of clinical infection? 

Tuncay Toprak, Aytaç Şahïn, Musab Ali Kutluhan, Korhan Akgul, Yavuz Onur Danacioglu, 
Mehmet Akif Ramazanoglu, Ayhan Verit

Department of Urology, Fatih Sultan Mehmet Training and Research Hospital, Istanbul, Turkey.

Objective: We investigated when an
indwelling ureteral catheter should be with-

drawn for infection and evaluated the importance of urinary
cultures in identifying colonized microorganisms and define
the bacterial flora encountered in the study. Moreover, this
study tried to determine the clinical role of stent culture in
clinical practice.
Material and methods: The study was conducted between June
2018 and February 2019. Patients with ureteral stent implan-
tation after endoscopic ureteral stone treatment were divided
into two groups and each group consisted of 45 patients.
Ureteral catheter was removed 15 and 30 days after ureteral
stone treatment in group 1 and 2, respectively, and transferred
for microbiological examination. The urine culture was
obtained before and after ureteral stent implantation. The
groups were compared in terms of demographics, urine and
catheter cultures results. Urine analysis and catheter culture
results were also compared. 
Results: Demographic data of patients were similar in both
groups. 3 patients in group 1 and 12 patients in group 2 had
positive urine culture before catheter retraction; 2 of 45 and 6
of 45 patients had positive catheter culture in group 1 and 2,
respectively. Although 2 patients in group 1 and 4 patients in
group 2 had urine culture sterile, they had growth in catheter
culture. In Group 1, 1 of the microorganisms was E. fecalis
and 1 was E. coli. In Group 2, 2 cases were E. fecalis, 3 were
E. coli and 1 was MRSE. There was no significant difference
between the urine analysis results of the patients before
catheter retraction and catheter culture positivity.
Conclusions: Pre-operative urine culture does not exclude
catheter colonization, and the prolonged duration of the
catheter associated with greater colonization and may be asso-
ciated urinary tract infection. Ureteral catheter should be
removed as early as possible.

KEY WORDS: Duration; Ureteral stents; Colonization.
Submitted 15 June 2019; Accepted 23 July 2019 

Summary

No conflict of interest declared.

DOI: 10.4081/aiua.2019.4.237

INTRODUCTION
Ureteral stenting is commonly used for drainage of the
obstructed or infected upper urinary tract. Although
ureteral stent application is not routinely recommended
after each ureteroscopy (1) ureteral stents were inserted
before the procedure to relieve pain to 7 to 68% of
patients who underwent ureteroscopy (2). Ureteral stent
is often colonized and incrustated, because it is in direct
contact with urine after insertion (3) and sterile urine
cultures do not exclude bacterial colonization on ureter-

al stents and postoperative urinary tract infection (4).
Many studies indicated there is no significant difference
between stents and urine cultures, complicating the
selection of appropriate antibiotics even when bacteria
are identified in urine culture (5, 6). We investigated
when an indwelling ureteral catheter should be with-
drawn for infection and evaluated the importance of uri-
nary cultures in identifying colonized microorganisms
and define the bacterial flora encountered in the study.
Moreover, this study tried to determine the clinical role
of stent cultures in clinical practice.

MATERIAL AND METHODS
This prospective study was approved by the institution-
al ethics committee of Fatih Sultan Mehmet Training and
Research Hospital (FSM EAH-KAEK 2019/13) and was
conducted between June 2018 and February 2019. 
All patients gave an informed consent for participation
in the study. Patients who underwent ureteral stent
implantation after endoscopic ureteral stone treatment
were included in this study. The patients who had posi-
tive urine culture before ureteral stone treatment and
who underwent ureteroscopy for other reasons and
patients who had diabetes mellitus, chronic renal dis-
eases, or immune suppression were not included in this
study. Patients were divided into two groups and each
group consisted of 45 patients. At the beginning and
before catheter retraction urine culture were obtained
from mid-stream voided urine. Stents were inserted and
removed under aseptic conditions with 22 Fr rigid cys-
toscope. Intravenous second-generation cephalosporin
was given 30-60 minutes before stent placement. 
A polyurethane double J stents (DJS; Uromed, Oststeinbek,
Germany) was used for insertion. Ureteral catheters were
removed 15 and 30 days after ureteral stone treatment in
group 1 and 2, respectively. The ureteral stents were
transferred to the microbiological examination immedi-
ately. Post-operative antibiotics were not given. Urine cul-
ture and ureteral catheter culture results of patients were
compared between groups. Urine analysis results and
catheter culture results were also compared. 

Statistical analysis
When evaluating the findings obtained in this study, IBM
SPSS Statistics 22 for statistical analysis (SPSS IBM, Turkey)

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Archivio Italiano di Urologia e Andrologia 2019; 91, 4

T. Toprak, Aytaç Şahïn, M. Ali Kutluhan, K. Akgul, Y. Onur Danacioglu, M. Akif Ramazanoglu, A. Verit

238

programs were used. The conformity of the parameters to
the normal distribution was evaluated by Shapiro Wilks
test. For evaluation of study data, Chi-Square test was used
to compare qualitative data as well as descriptive statistical
methods. Significance was evaluated as p < 0.05.

RESULTS
A total of 90 patients were included in this study.
Patients were randomized into two groups. Patients’
characteristics are summarized in Table 1. Male/female
ratio was 1.5 in group 1 and 1.25 in group 2. The mean
age was 45.6 in group 1 and 42.7 in group 2. No sig-
nificant difference was observed between the groups in
terms of age and gender. The urine culture of all patients
was sterile before catheter insertion. Urine culture taken
before catheter retraction was positive in 3 patients in
group 1 and 12 patients in group 2. Table 2 shows com-
parison of bacterial growth between groups. 
Patients with positive urine culture were treated with
appropriate antibiotics before ureteral catheter with-

drawal. Three patients with positive urine culture in
Group 1 had no bacterial growth in catheter culture after
antibiotic treatment. Two of 12 patients with positive
urine culture in Group 2 had the same microorganism-
induced growth in catheter culture after antibiotic treat-
ment. Although 2 patients in group 1 and 4 patients in
group 2 had urine culture sterile, they had growth in
catheter culture.
As shown in Table 3; one of the microorganisms isolated
from urine culture in Group 1 was E. fecalis and one of
was E. coli. In Group 2, 2 cases were E. fecalis, 3 were E.
coli and 1 was MRSE. The urine analysis of the patients
before the procedure was investigated for nitrite positiv-
ity, leukocyte esterase positivity and pyuria and com-
pared with catheter culture results. As shown in Table 4
no statistically significant difference was found between
catheter culture and urine analysis results. The duration
of surgical procedures ranged from 9 to 37 minutes, but
the relationship between the duration of surgery and col-
onization was not investigated. 

DISCUSSION
Ureteral stents are usually effective and safe in order to
deliver urine from kidney to the bladder. However, they
can lead to various complications, one of them being uri-
nary infection (7). After stent insertion biofilm formation
starts immediately, however, the time required for bacte-
ria to colonize the stent has not yet been defined (3).
Several studies showed the ability of uropathogens such
as E. coli, Proteus mirabilis, Staphylococcus epidermidis, and
Enterococcus faecalis to form biofilms on ureteral stents
within 24 hours (8, 9). Biofilm formation process on a
ureteral catheter is well defined by some studies (10),
and begins with the early development of the first mem-
brane on the catheter. Bacteria on this membrane can
more easily adhere and multiply. This environment pro-
tects bacteria from antibacterial factors (3) and bacteria
appear to be more resistant to antibiotics by developing
resistance genes to antibiotics (11). Consequently, it is
not surprising that stent colonization is frequently
encountered. In our study approximately 9% of our
patients hosted one microorganism and 87.5% of these
colonies included Gram-negative bacteria. This rate is
similar to rates described by other publications that are
below 50% for a mean catheterization time between 2
and 9 weeks (6, 12-14). Stent retention time in the ureter
increases the likelihood of biofilm formation and so the
duration of stenting is considered to be a critical factor
for bacterial proliferation (13). However, some reports
(6, 15) didn’t find a meaningful relationship between
positive cultures and catheterization time. In our study,
patients in group 2 had more bacterial growth in ureter-
al stent cultures than group 1 patients. Female gender in

Table 1. 
Comparison of demographic characteristics between groups.

Group 1 (n = 45) Group 2 (n = 45) P value
M/F (%) 60/40 55.5/44.5 > 0.05
Age, years, mean 45.6 (min 19 , max 73) 42.7 (min 23, max 76) > 0.05

Table 2. 
Comparison of bacterial growth between groups.

Group 1 (n = 45) Group 2 (n = 45) P value
Urine culture (at the All of them sterile All of them sterile
beginning or before ureteral 
catheter placement)
Urine culture (after ureteral 3 positive (6.6%) (2 of them women) 0.01
catheter placement or before 12 positive (26.6%) (8 of them women)
ureteral catheter retraction)
Catheter culture results 3 of them sterile 10 of them sterile
of patients with positive urine 
culture before catheter retraction 
(after antibiotic treatment)
Catheter culture in total 2 positive (4.4%) 6 positive (13.3%) 0.14

(1 of them women) (4 of them women)

Table 4. 
Comparison of catheter
culture and urine analysis.

Group 1 Group 1 P value Group 2 Group 2 P value
Positive catheter Negative catheter Positive catheter Negative catheter
culture (n = 2) culture (n = 43) culture (n = 6) culture (n = 39)

Pyuria (> 5 leukocytes) 1 (%50) 18 (%41.8) 0.82 3 (%50) 21 (%53.84) 0.86
Leukocyte esterase positivity 0 (%0) 4 (%9.3) 0.65 1 (%16.6) 3 (%7.6) 0.47
Nitrite positivity 0 (%0) 3 (%6.9) 0.69 2(%33.3) 5 (%12.8) 0.19

Table 3. 
Bacteriology of the cultured ureteral stents.

Group 1 - n (%) Group 2 - n (%)
Enterococcus fecalis 1(%2.2) 2(%4.4)
MRSE 0(%0) 1(%2.2)
E. coli 1(%2.2) 3(%6.6)
Sterile 43(%95.5) 39(%86.6)
Total 45(%100) 45(%100)

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various studies was found to be associated with a high
rate of sepsis as a result of the high infection rate in this
population (16). As expected, in our study 62.5% of
patients with positive ureteral catheter culture were
women, but we have not encountered symptomatic
infection or sepsis. The relationship between urine and
ureteral catheter cultures is not well defined. Lojanapiwat
(17) published urine culture results showing coloniza-
tion in approximately two-thirds of patients, whereas
Klis et al. (5) indicated a large inconsistency between
urine and ureteral catheter cultures. Our data supports
the discordance between preoperative urine and intraop-
erative stent culture. In this study, 6 patients had posi-
tive stent culture despite sterile urine culture. Sterile
urine culture in the presence of foreign bodies doesn’t
prevent stent colonization, and this may cause urinary
tract infection (18). Although some studies have report-
ed the opposite (15), in our study, the most common
pathogen in ureteral catheter cultures were E. coli and
Enterococci. In literature, there are also other publications
reporting that E. coli (4, 17) and Enterococci (6) are most
common in ureteral catheter culture. Kehinde et al. (19)
showed that bacteriuria and ureteral stent colonization
increased significantly with a longer stenting time,
female gender and presence of systemic diseases such as
diabetic nephropathy, chronic renal failure and diabetes
mellitus and recommended that patient of these cate-
gories should have shorter stenting time and antimicro-
bial prophylaxis to minimize infectious complications.
Another study (20) emphasized that early removal of the
ureteral stent, 2 weeks after renal transplantation,
reduced the rate of urinary tract infection. Although not
statistically significant our study gave similar results:
longer duration of stenting was associated to higher col-
onization rate (4.4% for stents left for 15 days versus
13.3% for those left for 30 days). None of our patients
had any systemic disease therefore the study of the cor-
relation between presence of pathologies and coloniza-
tion was not made. 
In conclusion, our study shows that results of urine cul-
tures do not represent the results of ureteral stent cul-
tures. E. coli is usually isolated and should be coated with
preoperative antibiotics. Our study demonstrates that
the stents are colonized under natural conditions and
that more awareness should be necessary before using
these stents. Our findings also showed that colonization
of ureteral stents was not associated with the develop-
ment of symptomatic infection. We didn’t found any
symptomatic infection after stent removal and we found
a colonization rate of 4.4% within 15 days and 13.3%
within 30 days.

Limitations of our study
We have given preoperative antibiotic treatment which
may have affected bacterial flora. Although a study (5)
showed that colonization throughout the stent is consis-
tent, we didn’t investigate different ureteral stent seg-
ments which could be colonized by different pathogens.
Our bacterial profile depends from local flora and could
be not transferable to other centers. Finally, stone cul-
ture was not done although bacteria within the stone
could affect ureteral colonization. 

CONCLUSIONS
The clinical significance of bacterial colonization of
ureteral stent seems to be low, and it seems that ureteral
stents are safer, especially within 15 days when colo-
nization is very low. Urine analysis and urine culture
results are not related with ureteral stent culture and
prolongation of ureteral stent increases colonization.
Further studies are needed to determine the optimal
indwelling time of ureteral stent after endoscopic ureter
stone treatment. Knowing the bacteriological flora of an
institution is useful for evidence-based prophylactic and
therapeutic application. It is not recommended to rou-
tinely send the stents to microbiological examination
because it is not cost effective and increases the workload
to the microbiology laboratory. Stents should be with-
drawn immediately if no more required.

Informed consent
Ureteral stent is frequently inserted after ureteral stone
treatment. Our study named ‘DOES STENT DURATION
INCREASE THE RISK OF CLINICAL INFECTION?’ will
investigate the relationship between the duration of these
ureteral stents with infection. The ureteral stent of some
patients will be taken 15 days after the stone treatment
and some of them will be taken 30 days later and sent to
the microbiological examination. Our research is multi-
centered and will be between September 2018 and
January 2019. A total of 100 patients were planned to be
included in the study. Patients will be randomized into
two groups. In the event of any unintended or unex-
pected health problems directly or indirectly related to
the research, any medical intervention will be provided
by us without any charge. You are completely free to par-
ticipate in the research. Failure to participate in this
study will not necessarily affect your current treatment
or relationship with your physician. You have the right
to withdraw from the work by giving notice at any time;
and if deemed necessary, you may be excluded from
research by the investigator, provided that your medical
condition is not harmed. If you participate in the
research, you will not be charged any fees or charges for
any expenses incurred in the study. The sample taken
from you for research will be used only for this study. In
addition, your information at the end of the research will
serve only scientific purposes without your identity
being disclosed.

Author's contribution
Toprak: Project development, Data Collection, Manuscript
writing; Şahin: Data Collection, Statistical analysis;
Kutluhan: Manuscript writing; Akgul: Revision; Danacıoglu:
Data Collection; Ramazanoglu: Data Collection; Verit:
Revision.

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Correspondence
Tuncay Toprak, MD (Corresponding Author)
drtuncay55@hotmail.com
Aytaç Şahïn, MD
draytacsahin@gmail.com
Musab Ali Kutluhan, MD
dr.musab151@gmail.com
Korhan Akgul, MD
korhanakgul@gmail.com
Ayhan Verit, MD
veritayhan@yahoo.com
Department of Urology, Fatih Sultan Mehmet Training and Research Hospital,
Istanbul (Turkey)

Yavuz Onur Danacioglu, MD
dr_yonur@hotmail.com
Department of Urology, Bakirkoy Dr. Sadi Konuk Training and Research 
Hospital, Istanbul (Turkey)

Mehmet Akif Ramazanoglu, MD
maramazanoglu@hotmail.com
Urology, Rize State Hospital, Rize (Turkey) 

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