Urosepsis is a urological emergency with various risk factors, including diabetes mellitus, immunosuppressant use, stones, and advanced age [5]. While urosepsis is more common in women and the prevalence is about twice as high in women as in men [11, 12]. In our study, we observed a significantly higher prevalence of urosepsis in women than in men, with a ratio of approximately 4:1, and some patients had concurrent diabetes mellitus. The mean age of patients in both groups was 59.36 years, and advanced age as a risk factor for urosepsis. Effective early goal-directed therapy for urosepsis involves broad-spectrum intravenous antibiotics, supportive treatment, and source control [13]. Surgical drainage of the infection source has been shown to reduce the mortality rate of urosepsis from 19.2 to 8.82% [6]. Stone is a common cause of urosepsis, and the current drainage methods for urosepsis caused by stones are RUS and PCN, but their superiority has been variable evaluations. In our analysis, we observed a rapid decrease in body temperature and WBC count to normal levels after emergency drainage, with no significant difference in the time required between the two drainage methods. Consequently, we concluded that there was no statistically significant difference in the effectiveness of the two drainage methods, consistent with the results reported by Ramsey and Pearle [9, 10].

During the performance of RUS for upper ureteral stones, especially in cases of multiple ureteral stones, it may be necessary to position the ureteroscope below the stone and insert a guidewire into the renal pelvis under direct vision to successfully place a D-J stent. Some prior studies have suggested that this approach could raise IPP, potentially worsening the infection [14]. However, other scholars argue that there is limited evidence to support this viewpoint [9]. In our study, as reviewed, we found no significant difference in the time to normalize body temperature and WBC count after drainage in both groups, indicating that drainage by RUS is safe. According to certain scholars, pre-stenting with a D-J stent in the ureter can enhance the success rate of UAS implantation and F-URSL [15]. In our study, certain patients encountered difficulties in placing the UAS during F-URSL due to ureteral stenosis, however, successful UAS placement was achieved after dilating the stenotic segment using a balloon dilator. All patients ultimately underwent successful F-URSL. The dilation of ureteral stricture segments using a ureteral balloon dilator has proven to enhance the success rate of UAS placement and reduce the need for secondary procedures [16].

Hydronephrosis resulting from urinary tract stones creates a conducive environment for bacterial growth and colonization, potentially leading to severe urosepsis [17]. Notably, most stones are heavily colonized with bacteria, with approximately half of the patients with positive stone cultures having negative bladder urine bacterial cultures [18]. Additionally, nearly a quarter of patients with positive preoperative urine cultures showed inconsistencies in the bacterial species between the stone and urine cultures [19]. Although preoperative treatment with sensitive antibiotics can effectively eradicate bacteria in the urine, it may not eradicate bacteria concealed within the stone matrix as antibiotics cannot penetrate it [20]. During F-URSL, fractured stones can release bacteria and endotoxins from the stone into the urine within the renal pelvis. When the IPP increases, the released bacteria and endotoxins can be carried back into the bloodstream along with the fluid, causing infection. Therefore, when managing stones with F-URSL in patients with prior urosepsis, reducing intraoperative IPP and minimizing the return of fluid to the renal pelvis, especially when complete elimination of bacteria from the stone is not possible, becomes crucial in minimizing postoperative infections.

In our study, both groups of patients who underwent F-URSL, the operative time and stone-free rate were similar, and there was no statistically significant difference in postoperative hospital stay and the rate of postoperative fever. This contrasts with the initial expectation that the incidence of postoperative fever would be lower in the PCN group than in the RUS group when F-URSL was performed after drainage due to the presence of a NT in the PCN group that could potentially reduce IPP. This outcome may be attributed to the use of a UAS during the procedure and the administration of longer and more potent antibiotics during the perioperative period. These factors likely contributed to the outcomes observed in our study. As all patients had prior urosepsis and indwelling D-J stent or NT, which were at increased risk of infectious complications after F-URSL [21,22,23]. However, there are no guidelines for perioperative antibiotic use in such cases. Therefore, to minimize the risk of infection, we referred to previous urine culture results and opted for potent antibiotics, such as piperacillin, as perioperative prophylaxis during F-URSL.

The physiological pressure in the renal pelvis typically ranges from 0 to 20 cmH2O [24]. During F-URSL, saline is infused continuously to maintain a clear surgical field, resulting in increased IPP. When IPP exceeds 27.2 cmH2O, fluid in the renal pelvis can return to the bloodstream via various pathways, including renal pelvic veins, renal tubules, and renal lymphatics [25]. Studies monitoring IPP during F-URSL revealed average values of 63 cmH2O when the endoscope was introduced into the kidney without a UAS, and 115.3 cmH2O during laser lithotripsy, with maximal irrigation pressures reaching 289.3-436.9 cmH2O [26]. High IPP is linked to postoperative fever, systemic inflammatory response syndrome (SIRS), and urosepsis [27,28,29]. The use of a UAS effectively reduces IPP. With the use of a UAS during F-URSL, IPP can be maintained below 30 cmH2O when the irrigation pressure is ≤ 100 cmH2O [30]. Research by Rehman et al. demonstrated the 12/14F access sheath provides for maximum flow of irrigant while maintaining a low intrarenal pelvic pressure. Even with an irrigation pressure of 200 cmH2O, renal pelvic pressure remained below 20 cmH2O [31]. Maintaining a low IPP depends not only on the size of the UAS, but also on the diameter of the flexible ureteroscope. When the ratio of the outer diameter of the flexible ureteroscope to the inner diameter of the UAS (Ratio of Endoscope-Sheath Diameter, RESD/REUS) is < 0.75, a low IPP can be maintained while ensuring adequate perfusion [32]. Therefore, we believe that during F-URSL, employing lower irrigation pressures, reduced flow rates, and an appropriately sized UAS can effectively maintain a lower pressure state in the renal pelvis, achieving similar effects as those of NT in lowering IPP, and reducing renal pelvic fluid reflux, subsequently reducing complications such as postoperative fever.

Our study demonstrated the effectiveness of both RUS and PCN in managing urosepsis due to stone obstruction. Additionally, we observed similar impacts of these drainage methods on subsequent F-URSL stone management. However, it is important to acknowledge the limitations of our study, being retrospective, single-center, and with a limited sample size, which might introduce bias. Therefore, future prospective studies with larger, multicenter populations are warranted to validate our findings more comprehensively.