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.