Discussion
In our study, we aimed to evaluate the ability of scoring systems to
predict postoperative success rate and infective complications that may
develop after RIRS. We concluded that RUSS and modified S-ReCS scoring
systems are insufficient in predicting infective complications. In our
study, although stone density, IUPA, IL, stone burden and stone
location, which are the parameters of the R.I.R.S scoring system, were
not found as independent risk factors for postoperative infective
complications, the R.I.R.S. score has been shown to be an independent
factor in predicting postoperative infective complications. To our
knowledge, our study is the first of its kind to confirm that a scoring
system can be used to predict infective complications after RIRS.
With the development of minimally invasive surgical techniques, scoring
systems have been developed to evaluate the postoperative success and
complication rates of the surgical methods used in the management of
kidney stones.5,9 The Guy’s stone score, Clinical
Research Office of Endourological Society nomogram, S.T.O.N.E score and
S-ReCS have been used as systems that can predict a SFR and
complications after PNL.10-12 Parameters that affect
the prediction of success rate and treatment selection have been
identified and are still in use for SWL, a surgical method that has been
used for a long time and continues to be used even
today.13
Although RIRS is accepted as a safe surgical procedure, postoperative
infective complications are the most common complications in RIRS with a
rate of 5.7%–18.3% in literature and can have fatal
consequences.8,14,15 However, it is understood that
systemic inflammatory response syndrome (SIRS) criteria are used for the
definition of sepsis and septic shock in these studies. However, at the
third international consensus meeting held in 2016 (Sepsis 3), it was
stated that the presence of organ dysfunction was an important parameter
in the differentiation of sepsis from uncomplicated infection and the
use of the total SOFA score instead of the SIRS criteria in this
differentiation was recommended.16 In our study, in
which the definition of sepsis was made according to the new criteria,
the postoperative infective complication rate was found to be 8.1%,
whereas 4.6% of the patients had only fever, 2.6% had urinary system
infection, 0.3% had sepsis and 0.5% had septic shock. To our
knowledge, our study is the first of its kind in which infective
complications after RIRS were defined according to the total SOFA score,
and we believe that the lower rate of patients with sepsis compared with
that in other studies is related to the use of this new classification.
Fan et al.17 reported that the stone burden is one of
the important risk factors for infective complications after RIRS.
According to Li et al.18, the bacterial load contained
in the stone increases and the risk of postoperative infective
complications increases as the stone burden increases. Demir et
al.19, in a retrospective study, evaluated 221
patients who underwent RIRS and found that the stone burden increased
the risk of postoperative infective complications by prolonging the
surgical duration and that the risk increased 11-fold in cases with a
surgical duration >61 minutes. Alezra et
al20. reported that the threshold value for this
surgical duration was 70 minutes. According to another study, a
prolonged surgical duration was found to have a cumulative effect in
increasing the pyelovenous reflux and transfer of bacteria from the
stone to the systemic circulation, thereby constituting the main
mechanism for postoperative infective complications.21According to our study, a surgical duration of >60 minutes
increased the risk of infective complications 1.9 times and was found to
be an independent risk factor. If the stone burden is >200
mm2, more infective complications are seen. Despite
this, the stone burden has not been determined as an independent risk
factor for infective complications. Accordingly, it can be concluded
that the increase in the infective complication rate in cases with a
high stone burden is due to the prolonged surgical duration.
In a study on 337 patients in whom risk factors for SIRS and fever
occurring after RIRS were evaluated, the mean age of patients who
developed SIRS was 51.2 ± 10.5 years, whereas it was found to be 53.1 ±
13.3 years in patients who did not, and the difference was not
statistically significant (18). Similarly, in another
prospective study, no difference was found between the mean age of
patients with and without postoperative symptomatic urinary tract
infection.22 In our study, postoperative infective
complications were seen 1.8 times more in patients aged >50
years compared with those aged <50 years, and this difference
was statistically significant. Due to the higher number of patients in
our study compared with that in other studies, we believe that achieving
such a result, unlike that observed in literature, may be related to the
weakening of the immune system and increased susceptibility to clinical
infections.
When the relationship between a history of treated urinary tract
infection and postoperative infective complications was examined in a
multi-center prospective study by Cai et al.22, it was
found that that a history of treated urinary tract infection was not a
risk factor. Again, the study by Li et al.18 supports
this result. However, Grabe et al.23 reported that
previous urinary tract infection is an important risk factor. In
contrast, no relationship was found in our study.
Congenital kidney anomalies have been shown as risk factors for
postoperative infective complications in some
studies.5,24 In our study, only fever was observed in
1 of the 14 patients with congenital kidney anomalies, whereas no
infective complications were observed in others. However, the low number
of patients with congenital kidney anomalies in our study makes it
difficult to comment on this issue.
Our study has some limitations. The retrospective design of our study
and the fact that all surgeries were performed in a single centre are
the major limitations. Other limitations include the use USG and KUB
radiography, which may have had low sensitivity, in the evaluation of
residual kidney stones. However, the fact that it is the first study, to
our knowledge, in which a scoring system was used to predict
postoperative infective complications after RIRS makes our study unique
and insightful.