Discussion
Renal and proximal ureteral stone disease is a common condition worldwide. The lifetime risk of urolithiasis is 13% in men and 7% in women [11]. In recent years, RIRS is widely used in surgical procedures in urology, as in other surgical departments, due to the tendency toward minimally invasive options. RIRS has been compared with other therapeutic modalities in terms of stone-free status and complications [12,13]. The stone-free rate of this surgical procedure in our series was 83.6%, and the final stone-free rate after re-procedure was 94.4%. In the literature, the stone-free rate is reported to range from 69.7 to 97% [14-16]. Although minor complications are common after RIRS, major complications such as severe bleeding and sepsis may also develop [17]. Breda et al. reported complications in 8% of the patients after RIRS, and major complications were present in 1.9% [18]. SCS and MCCS are the most widely used surgical complication classification systems in the urology discipline [9,10,19]. Although there are a few studies reporting complications related to the use of flexible ureteroscopy, only limited research has attempted to standardize complications using these new classification systems. In our study, the incidence of intraoperative events or complications was 153 (16.1%) according to SCC and the incidence of postoperative complications was 121 (12.6%) according to MCCS.
In a recent study by the Clinical Research Office of the Endourological Society, the data of 11,885 patients (1852 with only renal stones, 8676 with only ureteral stones, and 1145 patients with both types of stone), who underwent ureteroscopy in 114 centers in 32 countries, were prospectively examined [16]. The postoperative complication rate was reported as 3.5%, and most of the cases that developed complications were Clavien grade 1 or 2 (2.8%). Intraoperative complications were also reported separately, including bleeding (1.4%), perforation (1.0%), ureteral avulsion (0.1%), and conversion to open surgery (0.1%). The most frequent complication in that series was fever (1.8 %). Bleeding was reported at a rate of 0.4%, and a blood transfusion was required in 0.2% of patients. In addition, sepsis developed in 38 (0.3%) patients, and mortality in five patients for various other reasons. SCS is the most common classification system used in classifying intraoperative adverse events [9]. In our series, Satava grade 1 was seen in a total of 60 patients. However, there were six (0.6%) patients with malfunctioning or breakage of instruments in the Satava 1 group. We consider that it is not appropriate to evaluate this as an intraoperative complication. This situation should be referred to as an intraoperative event, not as a complication. In addition, the most common intraoperative complication in our patients was minimal mucosal injury (3.7%). However, grade 3 complications were not observed. The most common grade 2b complication was requirement of repeat RIRS (5.6%) after the stone could not be accessed for various reasons. Among the patients with grade 2b complications, the surgery had to be terminated early in six (0.6%) due to vision impairment caused by severe bleeding. Nevertheless, all of these bleedings were self-limited and did not require a blood transfusion or surgical intervention. While minimal mucosal erosions or tears (grade 1) can heal conservatively without a DJ stent, severe mucosal injuries, such as ureteral perforation (grade 2), are mostly treated by placing a DJ stent. In a study by Ural et al., mild mucosal injury was seen in only 10 (4.3%) patients, and serious mucosal cleft was observed in three (1.3%) patients and treated by inserting a urethral DJ stent [17]. In our cases, mild and severe mucosal injuries were rare, similar to the literature. Traxer et al. reported that preoperative ureter stenting reduced the risk of severe ureteric injury by 7 times [13]. In our study, no statistically significant relationship was found between preoperative stenting and absence of complications, and the relationship between preoperative DJ insertion and ureteral injury was not evaluated in our series. Although SCS includes the minor complications mentioned above, conditions such as fever and sepsis are not classified in this system. We consider that SCS evaluates whether the outcome of the operation is a success because it is based on whether the operation is to be completed then or postponed. We think that malfunctioning or breakage of instruments is not a complication, and therefore they should not be included in SCS.
Breda et al. reported the overall complication rate for RIRS as 8% and the major complication rate as 1.9% according to MCCS [18]. In a prospective randomized study by Sabnis et al. conducted with 35 patients that underwent RIRS, the rate of Clavien grade 1 complications was determined as 11.4%, but no other complication was reported [20]. In our series, 76% of the patients that developed complications were classified as grade 1. Major complications were observed in 18 (1.9%) patients. Two patients had a ureteral stricture (0.2%), one had urosepsis (0.1%), and a further two died due to urosepsis (0.2%). Therate of postoperative fever resolved with an antipyretic was consistent with the literature in our study, but the rate of fever requiring antibiotic replacement (grade 2) was lower in our study [21]. In a study by Tian et al., the rate of fever was found to be 17.5%, and diabetes mellitus, elevated preoperative C-reactive protein (CRP), high stone burden, positive stone culture, and positive renal pelvis culture were shown to be among the reasons that could cause fever [22]. In another study, Yong et al. showed that operative time was an important factor for postoperative fever [21]. In our series, operative time was longer in the complication group. In the subgroup analysis performed, operation success was found to be the factor affecting major (>grade 3) complication. We consider that factors that affect the success of the operation, such as stone size and density, also indirectly affect the probability of major complications.
In the literature, postoperative hematuria has been reported at a rate of 5-7.1%, and it has been emphasized that the use of stone burden, a high CT attenuation value, or use of UAS increased the incidence of postoperative hematuria [21,23]. In a study conducted by Shah et al., it was stated that postoperative hematuria was common in patients with stones of high CT attenuation, which was caused by increased mucosal damage as a result of more effort being required to fragment the stone [24]. In our study, postoperative hematuria was the second most common complication with a rate of 3.6% and was found be related to increased stone burden, presence of residual stone, and operative time while there was no relationship between the use of UAS and postoperative hematuria development. Although postoperative hematuria is more common in patients with low CT attenuation values, it is evaluated as borderline non-significant. This situation can be explained by the prolongation of operative time as a result of the decrease in the detection of stones with low HU values ​​on fluoroscopy. This idea is supported by the statistically significant negative correlation between HU and operative time and the significant relationship between operative time and postoperative hematuria development.
Although other complications are extremely rare, they can lead to serious situations if they occur. Post-RIRS sepsis is one of the most serious complications [25]. In a retrospective study by Fan et al., sepsis was seen in two (0.88) patients after RIRS, and the infective complication rates were found to vary between 1.7 and 18.8% [26]. Berardinelli et al. reported the rate of sepsis to be 0.7% [27]. In our series, sepsis was observed in three (0.3%) patients, which is consistent with the literature. In studies evaluating factors related to the development of infective complications, pyuria, operative time, infection stones, diabetes mellitus, elevated preoperative CRP, high stone burden, and positive stone culture were found as independent predictive factors [22,26]. In addition, another major complication, steinstrasse, was observed at a rate of 1.9% in aprevious study [21]. In our study, non-obstructive steinstrasse was detected at a rate of 0.6% and obstructive steinstrasse at 0.5%. Ural et al. determined that the rate of major complications according to SCS was 8.9% [17]. Abnormal renal anatomy and presence of multiple stones each increased complication development by 2.7 times while the stone-free status decreased complication development by 4.2 times. According to MCCS, stone-free status was determined as an independent predictive factor in the development of major complications. In addition, according to SCS, stone size, stone density, and fluoroscopy time were independent risk factors in predicting the requirement of endoscopic, open or laparoscopic treatment.
The main limitations of our study are that it had a retrospective design and the operation was performed by specialists with different surgical experience. Another limitation is that we did not examine factors that had been previously shown to be associated with the development of complications, such as CRP, stone culture, and stone type, nor did we evaluate late-term complications.