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.