Statistical analysis
All statistical tests were performed using SPSS Statistics version 24
(IBM, Armonk, NY, USA) software. The sample mean was used to determine
the average of collected data as quantitative variables met the normal
distribution; otherwise, the sample median was used. A chi-square test
was performed for nominal variables in the groups. A Student’s t-test
was applied to make group comparison when the normality assumption was
satisfied for both groups. If the normality assumptions were not
satisfied for either group or both groups, the equivalent nonparametric
Mann-Whitney U test was applied.
Binomial logistic regression was then performed analysing the
statistically significant univariate factors. Predictors that obtained
significance for surgical success were entered into a multivariable
logistic regression model to determine the independent predictors.
RESULTS
The study consisted of 422 consecutive patients (113 in Group 1; 289 in
Group 2) that meet the criteria for inclusion. Of these, 179 (42%) were
females and 243 (58%) were males, with a mean age of 48.8 ± 14 (14–80)
years. Patients’ demographics, baseline stone status and characteristics
and operative outcomes are presented in Table 1.
Group 1 (sURS group) and group 2 (non-sURS group) patients’ comparisons
are also listed in Table 2. There was no statistically significant
difference between the two groups in terms of stone and patient
characteristics. However, the mean operation time was significantly
longer in the sURS group (87.1±37min vs 67.3±27 min,p<0.0001 ). Fluoroscopy times were similar between the
groups (p=0.53 ). UAS was unable to be placed in four (3.0%)
patients in the sURS group and 25 (8.7%) patients in non-sURS group
(p=0.03 ). In the non-sURS group a fURS was unable to be inserted
through a working guidewire in two patients whose UASs were unable to be
placed as well. The JJ stent was placed and reoperation was planned in
these patients. While the surgical success was 94.7% in the sURS group,
it was 84.1% in the non-sURS group, and this was statistically
significant (p=0.002 ). The intraoperative complication rate was
lower in the sURS group than in the non-sURS group (1 (0.8%) vs 14
(4.8%), p=0.04 ). In the sURS group, the stone could not be
properly visualized in one (0.7%) patient due to intraoperative
bleeding. The complications observed in the non-sURS group included
eight (2%) mucosal injuries requiring stent insertion, two (0.6%)
postoperative prolonged haematuria, two (0.6%) collecting system
perforations requiring JJ stent placement, one (0.3%) inability to
reach stone and one (0.3%) converted to percutaneous nephrolitomy in
the same session. Although postoperative complications were lower in the
sURS group compared to the non-sURS group, this was not statistically
significant (5 (3.8%) vs 23 (8.0%), p=0.10 , respectively). The
postoperative complications for the sURS group were: fever requiring
antibiotic (n=2, 1.5%), renal colic requiring analgesic (n=2, 1.5%),
gross haematuria not requiring transfusion (n=1, 0.7%); for the
non-sURS group: fever requiring antibiotic (n=7, 2.4%), renal colic
requiring analgesic (n=10, 3.4%), gross haematuria not requiring
transfusion (n=5, 1.7%) and urosepsis (n=1, 0.3%).
The results of univariate analysis of the factors affecting surgical
success are presented in Table 3. Although the surgical success was
determined to be significantly affected by the optical dilatation
through sURS, it was not significant in multivariate analysis (in
univariate analysis: p=0.002 , in multivariate analysis:p=0.179 ). We have found two independent factors predicting
surgical success in multivariate analysis. These were stone number
(p<0.0001, odds ratio: 2.28 and 95% CI
[1.48-3.49]) and failed UAS placement (p=0.035, odds ratio:
3.49 and 95% CI [1.04- 11.14]) (Hosmer-Lemeshow test:p=0.378 ).
DISCUSSION
This study is the first research investigating the impact of optical
dilatation with sURS on the operative outcomes of RIRS. Our study has
revealed two important issues regarding the use of sURS in patients
undergoing RIRS. First, when using sURS, UAS is more easily placed into
the ureter, and the surgical success rate increases. However, it is not
an independent predictor of surgical success. Second, intraoperative
complication rates are found to be low.
One of the most essential components of RIRS surgery is the placement of
UAS. The use of UAS makes a positive contribution to the operative
visibility, stone-free rate, and operation time without increasing the
complication rates [ 1,3,4,11]. Furthermore, it is stated in several
reports that the utilization of a UAS may have a positive impact on
complication rates [8,12]. However, the insertion of a UAS can
sometimes be challenging. The authors recommend various strategies to
address this problem. Passive ureteral dilatation made with routine
stent placement can be safe and efficient, but this method carries the
risks of secondary anaesthesia, an operation, and eventually higher
costs [1,11]. In addition, stent-related symptoms may be seen, such
as prolonged haematuria, flank pain, dysuria and urgency, and patients
are usually not willing to accept presenting when they hear about these
side-effects [4]. Placement of UAS following active dilatation with
a balloon or a coaxial dilator is not routinely recommended because of
the risk of significant ureteral injury [1,5]. In the EAU guidelines
for approximately 10 years it has been advised that sURS before RIRS can
be helpful for optical dilatation. The direct visualization of the whole
ureter by semirigid ureteroscopy just before the UAS placement is not
only to provide optical dilatation but also allow to evaluation of any
additional stones, strictures, or tumours in the ureter [11].
Moreover, it can also help with evaluation of ureteral compliance and
diameter [5].
Due to a difficult impassable ureter, the failure rates of primary
access of UAS range from 6% to 22% in the literature [1,5,13].
Success rates increase when the appropriate diameter is determined with
sURS and when a thinner UAS is used in cases where it is needed [5].
However, the preferred UAS must be narrow enough not to damage the
ureter, but wide enough to clean the stone and provide intrarenal
circulation. The most reliable method to determine appropriate UAS
diameter is to evaluate with sURS. Lima et al. recommend a routine sURS
for passive ureteric dilatation and selection of the correct UAS size
[8]. In our study, in accordance with the literature the UAS failure
rates are 8.7% in the non-sURS group and 3.0% in the sURS group.
Diameters of sURS used in the study are 8 or 9.5 fr in circumference at
the distal tip and 12 fr in circumference at the proximal tip. We think
that the mechanism of cascading diameter increase dilates the intramural
ureter, the narrowest and least elastic part of the ureter, without
damage shown in Figure 1.
Despite all these advantages of UAS, there are some drawbacks. One of
these is deterioration of ureteral blood flow. Lallas et al. show
transient decreased ureteral blood flow secondary to the use of a UAS in
animal models [14]. However, they stated that the compensatory
mechanisms of the ureteral wall restored the blood flow of the ureter
wall and the integrity of the ureter was preserved. The authors
concluded that the use of a UAS with RIRS might be safe; however, care
must be taken in selecting an appropriate size of sheath and the
duration of surgery should not be prolonged because of the risk of
stricture development. In our study, the duration of the operation was
found to be significantly higher in the sURS group than in the non-sURS
group (the difference between means: 20 min, p<0.0001 ).
The extended duration of the operation is thought to have been spent on
sURS, but unfortunately the duration of UAS placement has not been
measured.
Another drawback associated with UAS is the risk of ureteral injury
during entry. Traxer and Thomas prospectively evaluated ureteral
injuries secondary to insertion of a 14F UAS [15]. The authors
reported that ureteral wall injuries occurred in 46.5% of the patients,
and that the most significant predictor of severe ureteral injury was
the absence of stenting before RIRS. However, in another prospective
study on 2239 patients treated with fURS, Traxer et al. found that UAS
usage did not increase the risk of ureteral wall damage, and
postoperative infectious complications were reduced [16]. In a
retrospective study in which 4500 RIRS procedures were evaluated,
intraoperative incidents occurred during 5.2% of the procedures, and
overall complications occurred in 18.9% [12]. The authors reported
that in 4.8% of the cases in which a ureteral access sheath was used
they encountered grade 2 and 3 ureteral wall lesions. In our study,
while one (0.7%) intraoperative complication (inability to reach stone)
was observed in the sURS group, 14 (4.8%) intraoperative complications
were observed in the non-sURS groups and the majority of these
complications were mucosal injury (57%). We suppose that optical
dilatation with sURS and selection of the correct UAS size reduce the
intraoperative complications. Although the rates of postoperative
complications in the sURS group were lower, there was no statistical
difference between sURS and non-sURS groups.
In many studies, factors that predict stone-free and surgical success
have been investigated. In some studies stone size, presence of lower
pole calculi, surgical experience, presence of hydronephrosis, and UAS
use are significant predictors of RIRS outcome, while others have only
found the number of stones and the number of sites [17-19].
Especially thanks to the advances in the field of lasers, stone access
is the most important factor that makes treatment possible. In our
series, the mobile lower pole stones were repositioned into the upper or
middle calyx. This method may have reduced the impact of localization on
the stone-free rate. In our study, UAS usage and the presence of
multiple stones were found as independent predictors for surgical
success. The failed surgery rates have increased 2.28 times as the
number of stones increases, and have increased 3.49 times when the UAS
cannot be placed. It is expected that the use of sURS before RIRS
increases surgical success by increasing the rate of UAS placement and
reducing the rate of intraoperative complications. Finally, we found
that the surgical success rate was higher in the sURS group (p=0.002).
However, our study found that sURS had no independent effects on the
surgical success of RIRS.
CONCLUSION
As a result, the optical dilatation with sURS, which is also recommended
in EAU guidelines, makes a positive contribution to surgical success,
facilitating UAS placement and leading to a low complication rate.
Although it requires longer surgery time, we recommend this method, with
acceptable fluoroscopy time, in patients with no previous history of
passive dilatation using a JJ stent. However, further randomized
prospective studies are needed.