Results
The characteristics of the patients and stones are shown in Table 1. The mean age of the patients was 47.2 years, and the female/male ratio was 346 (36.5%)/603 (63.5%). Of all patients, 87.9% had an ASA score of I and II, 104 had ASA III and 11 had ASA IV. The median stone size was determined as 13 mm. The stone size was 10 mm or below in 38.9% of the patients, 11-20 mm in 41.4%, and larger than 20 mm in 19.7%. Two or more stones were present in 297 (31.3%) of the patients. The most frequent primary location of the stones was the pelvis (23.1%), followed by the lower calyx (20.7%), proximal ureter (18.5%), multicaliceal (13.9%), middle calyx (8.2%), both the kidney and ureter (7.5%), and upper calyx (5.0%).
The perioperative and postoperative data are presented in Table 1. The median operative time and fluoroscopy time were 45 min and 20 sec, respectively. UAS were used in 76% of the patients and postoperative stents in 92.6%. While the stone-free rate was 83.6% after the first intervention, the final stone-free rate was 94.4% after re-procedure.
According to SCS, the incidence of intraoperative event and complications were 153 (16.1%). The classification of these complications according to the SCS system is shown in Table 2. There were 6.3% grade 1, 2.7% grade 2a and 7.1% grade 2b complications. While mild bleeding (2.0%) and minimal mucosal injury (3.7%) were the most common grade 1 complications, recurrent RIRS requirement (5.6%) after inability to reach the stone due to various reasons was recorded as the most common grade 2b complication. Grade ≥2b complications according to SCS, significant predictors were stone size (OR:1.066, 95% CI =1.036-1.098) (p <0.001), stone density (OR:0.999, 95% CI = 0.997-1.000) (p =0.022), and fluoroscopy time (OR:1.007, 95% CI=1.003-1.011) (p <0.001).
Postoperative complications occurred in 121 (12.8%) patients. The classification of complications according to MCCS is presented in Table 2. Minor complications (grade 1 and 2) developed in 10.8% of the patients. Major complications were observed in 18 (1.9%) patients. Ureteral stricture (0.2%) developed in two patients. In addition, two of three patients that developed urosepsis died as a result of multi-organ failure.
Table 3 shows the comparison of possible factors related to complications. The mean age was found to be significantly higher in patients with complications. Complications were higher in patients with renal anomalies (9.9% vs 3.9%, p = 0.006). Stone localization was also associated with the development of complications. In the subgroup analysis of stone localization, lower complication rates were detected for the stones located in the pelvis (14.9% vs 24.9%) and proximal ureter (10.7% vs 19.7%) while multicaliceal (24% 12.4%) and pelvic + single caliceal (7.4% vs 2.5%) stones had significantly higher complication rates. Stone size, number and density were determined to be associated with the development of complications (p <0.001, p <0.001 and p = 0.002, respectively).
Table 4 presents the results of the multivariate analysis of the parameters determined to be associated with the development of complications. Abnormal renal anatomy, multiple stones, operative time, and stone-free status were determined as the independent indicators of complication development. Complication development was increased by 2.7 times by abnormal renal anatomy and presence of multiple stones while it was decreased by 4.2 times by stone-free status (p = 0.010,p <0.001, and p <0.001, respectively). The multivariate analysis revealed that for the patients with grade ≥3 complications according to MCCS, only stone-free status was a significant predictor of complication development [odds ratio (OR):0.347,95% CI=0.124-0.974] (p =0.044).