Laser and pneumatic are the most dependant lithotripters. EAU recommended Ho:YAG laser lithotripsy as a gold standard procedure for ureteroscopic intracorporeal lithotripsy because of its efficiency to fragment all stone types, ablative effect and stone dusting [9]. However, pneumatic energy is stronger and cheaper than Ho:YAG laser with minimal tissue trauma [10,11,12,13]. These different lithotripter mechanisms (mechanical vs. photothermal) affect the stone-free and upward migration. Purpurowicz and Sosnowski reported that preoperative factors such as hydronephrosis, stone size and stone location are the most commonly affecting outcomes [14]. On the other hand, De et al. emphasized that the operative factors and the technique are the more important [15]. Accordingly, combining two techniques, PL and LL not only increase the safety but also preserve the efficiency. In terms of SFR, the combined group had a nearly similar early SFR, 62.2% versus 57.7%, and the rate had been increased to 88.8% versus 91.1% for late SFR in laser and combined groups, respectively, which is statistically insignificant (p ≥ 0.05). Hui et al. use the combined pneumatic lithotripsy and Ho:YAG laser for treating 232 patients with ureteral stones and reported 89.9% SFR which is comparably well with SFR of the combined group [16]. Degirmenci et al. compare laser and pneumatic lithotripsy for treating impacted ureteric stones and reported a distal ureteral stone-free rate of 96.8% and 91.7% for laser and pneumatic, respectively [4]. Their relatively higher SFR may be because of the smaller stone size in their series, in addition to our strict definition of stone-free status. The strategy in the combined group is to perform stone disimpaction via PL; then, laser replaces it to complete the fragmentation process. This is playing an important role in reducing not only thermal tissue injury related to laser but also stone retropulsion related to PL. Stone retropulsion met with was similar 4.4% for each group and this is comparably well with finding recorded by Degirmenci et al. who reported nearly similar retropulsion rate 6.8% (5 out of 73) and 6.4% (4 out of 62) for Pl and LL, respectively, when treating distal impacted ureteral stone [4]. Li et al. reported 24% and 21% retropulsion rate, respectively, with insignificant statistical difference [10]; their higher rate may be related to the inclusion of patients with mid ureteric stones in addition to distal position and their relatively smaller stone size. Ureteral tissue reaction and associated limited working space due to stone impaction increase the likelihood of ureteral mucosal injuries or perforation even when gentle procedure is performed [17]. The operative complications were higher in the laser versus the combined group, 11.11% vs. 4.4%, respectively, which is statistically significant (p ≥ 0.05); this is may reflect the safety of the heatless mechanism of pneumatic lithotripsy device when the working field is narrow due to stone impaction. No ureteral perforation was seen in combined group, but it is encountered in one patient 2.2% in the laser group. The operative complication rate is comparably well with that reported in the literature which ranged widely from 4 to 28.4% [18, 19]. Operative complications were treated by termination of the procedures as early as possible and 6 Fr DJ stent fixations which kept in place for 2 to 6 weeks; then, second session was attempted. Postoperative complication rates in laser and combined groups were 13.3% and 8.8%, respectively, which is statistically significant (p ≤ 0.05). Brito et al. [11] reported stricture rate 4.7% after PL, and Fam et al. [17] reported a stricture rate of 7.7% after LL when treating impacted lower ureteric stones. Stricture ureter was developed in two patients (4.4%) in laser group. One had a ureteral perforation and responded successfully to ureteral balloon dilatation and DJ stent fixation, while the second had a perforation on top of extensive mucosal laceration with stone particles inevitably buried in the mucosa and was only responded to ureterovesical re-implantation. No perforation was recorded, and no stricture was detected in the combined group; the link between perforations and strictures had been observed by many authors, who commented that stricture rate is directly related to the nature of complications that developed intraoperatively, in particular ureteral perforation and lodging of the stone particles in ureteral mucosa which support our findings [11, 17].
Cevik et al. did not recommend DJ stent routinely after uncomplicated ureteroscopic lithotripsy for impacted ureteral stone [20]. In this study, we widen the indications of DJ stenting, so we fix it even when the mucosal injury is not extensive to allow ordered ureteral healing and avoid stricture development. DJ stenting was significantly less in the combined relative to laser group, 51.1% versus 64.4%, respectively, which matches the finding of Irer et al. who reported that DJ stenting was significantly lower in their pneumatic group versus laser [13]. The goal of lithotripsy process is to produce small stone chunks that can be passed out spontaneously or easily retrieved, this goal is still easily achieved in both groups, and the lithotripsy time and operative time (mean ± SD) were nearly the same in laser and combined groups (15.5 ± 12.2 vs. 17.3 ±7.2) and (40.7 ± 26.3 vs. 43.2 ± 21.6) minutes, respectively. Many authors reported shorter lithotripsy time of pneumatic relative to laser; however, regarding the operative time the reverse was recorded because of the relative big stone chunks produced by PL which required is to be removed [21,22,23]. This is not the case in the current study since LL continues playing the major role in the fragmentation process with the production of stone fragments small enough to pass spontaneously. Stone impaction may be associated with bleeding from the inflamed friable mucosa that causing impaired red field of vision which occasionally necessitates early termination of the procedure, and a second session of ureteroscopic lithotripsy is indicated. Second session lithotripsy was lower in the combined than laser group, 8.8% versus 15.5%, respectively. Legemate et al. [24] reported 11.6% versus 8.1% re-treatment rate when comparing impacted versus non-impacted ureteric stones, respectively; using either PL or LL which is comparably well with our finding, Chen et al. [25] reported a higher re-treatment rate 48.5% versus 25% for PL and LL, respectively, which may be related to the proximal stone location in addition to the operator factors. The hospital stay was within the range of that reported in the literature [10, 26]. We found a nonsignificant decrease in the combined group versus laser group which may be due to fewer complications in such group; this rationale is supported by Abedi and his colleagues [26]. The limitations of this work are the small patient’s number, non-uniform surgeon’s experiences, the potential errors that may be introduced during stone size estimation because of two different imaging modalities (X-ray and NCCT), short duration of follow-up and non-categorized postoperative complications according to Clavien’s system, and, in addition, the absence of standardization regarding the definition of the stone impaction and the stone-free status.
