Discussion
RIRS is an emerging surgical technique for the treatment of upper
urinary system stone disease. Despite its invasive nature, the
preference rate of RIRS has increased significantly [2]. On the
other hand, many urologists prefer ESWL as the first-line treatment of
proximal ureteral stone disease. It is scientifically reasonable that
the EAU guidelines recommend ESWL and ureteroscopy as equally valid for
the treatment of proximal ureter stones <10 mm [6]. For
that reason, many patients undergo ESWL for proximal ureteral stone
disease, and RIRS becomes the second-line treatment modality for
patients in which ESWL is unsuccessful.
Although ESWL is defined as a non-invasive procedure, it has some
destructive effects on tissues [10]. Studies have demonstrated that
the shock waves might lead to microvascular damage and shear effect at
the tissue around the stones [11,12]. The traumatic effect of ESWL
has also been clinically observed. Nearly all ESWL sessions cause
microscopic or macroscopic haematuria. Experimental studies have
demonstrated that uroepithelial irritation was not the only reason for
hematuria, the main reason was microvascular damage and local trauma
[11]. Histomorphologic studies showed that shock waves induce torn
vessels with platelet aggregation; vacuolization to complete necrosis of
the epithelium and vascular smooth muscle; and aggregation of red blood
cells and leucocytes in the interstitial space [13]. Although these
findings have been shown in the renal parenchyma and papilla, the
ureteral wall might also be exposed to similar reactions after ESWL
treatment of ureteric stones. Ureteral stricture is a devastating
complication of ESWL, which might be the result of an extreme reaction
that occurs due to tissue damage from the shock waves [14].
One of the main questions of our study was: “Does the presence of
pre-RIRS ESWL complicate the RIRS procedure?” The peroperative
variables, such as operation time and peroperative complication rates,
were similar between the groups. The postoperative variables, such as
postoperative complication rates and hospitalization time, were also
similar between the groups. These data revealed that performing ESWL
before RIRS did not complicate the surgical procedure for proximal
ureteral stone disease. On the other hand, the fluoroscopy screening
time was nearly twice as long, with a significant difference in patients
who had undergone ESWL before RIRS. This data showed that surgeons had
to use more fluoroscopy during RIRS for patients who have undergone ESWL
before the surgery. The importance of radiation exposure during the
surgery is a well-known phenomenon by surgeons, and all surgeons try to
obey the ALARA (As Low As Reasonably Achievable) principles. For that
reason, the significant difference in radiation time between the groups
might demonstrate that the surgeons of our cohort had to be more
cautious during RIRS performed after ESWL. This finding was an important
output of our study. Although the operation time and peroperative
complication rates showed that pre-RIRS ESWL did not complicate the
surgical procedure, surgeons had to use more radiation during the
procedure for patients who had previously undergone ESWL.
Another question that we tried to answer in this study was: “Does the
presence of pre-RIRS ESWL affect the stone-free rates of RIRS?” The
stone-free rates were similar between the groups, which showed that the
performance of ESWL before the surgery did not affect the surgical
success. On the other hand, the time from the ESWL and RIRS had a
predictive effect on the success rate of RIRS. The stone-free rates of
RIRS for proximal ureter stones increased as the duration between ESWL
and RIRS increased. The authors found that the OR for stone-free status
was 1.27 for each preceding week, and the threshold time was 10 weeks
with 51% sensitivity and 88% specificity. To our knowledge, this study
is the first in the literature documenting the relation between
stone-free status and the duration between ESWL and RIRS. As the
proximal ureter stones may lead to hydronephrosis and a heightened risk
for renal dysfunction, it may not be logical to wait for 2 months after
the ESWL to perform RIRS. On the other hand, this data may be important
to predict the success of RIRS. For the patients who have very recently
undergone ESWL, inserting a double J stent and postponing the surgery
for a while may be a solution to increase the stone-free rates of
patients.
There have been some studies evaluating the predictive factors of the
efficacy and safety of semirigid ureteroscopy for the treatment of upper
ureteral stones. The variables related to stone migration, such as the
length and diameter of the proximal ureter portion, stone size and
surgeon’s experience, were the main predictors for the success rate of
semirigid ureteroscopy [15]. Stone migration has limited importance
for RIRS because the flexible nature of the ureteroscopes let the
surgeons follow the migrated stone and complete the surgery. Although
semirigid ureteroscopy and RIRS have similarities in terms of technical
principles, they are totally different in terms of surgical procedure.
For this reason, it is hard to compare the predictive factors for the
success of semirigid ureteroscopy with RIRS.
The retrospective design and relatively limited study population were
the main limitations of our study. However, the study data were obtained
from the RIRSearch database, which was prospectively created with
detailed evaluation. Another limitation was the lack of ESWL
standardization in our study group. The patients had undergone ESWL
sessions in different institutions, which impacted the standardization
of the procedure. However, it is a reality that surgeons have to perform
RIRS on patients who have undergone ESWL in different clinics without
standardization. We believe that this study is valuable because it
represents the first investigation evaluating the effect of pre-RIRS
ESWL on the results of RIRS in the treatment of proximal ureter stones.