In 1983, Bagley et al. from the University of Chicago in the United States developed the first flexible ureteroscope by integrating the working and perfusion channels. Since then, fURL has gradually become a crucial surgical technique for the treatment of upper urinary stones [10]. Ureteral stent is widely recognized for its ability to facilitate the passage of residual stones and promote the healing of ureteral mucosal injuries. Moreover, it serves as a preventive measure against infection, pain, and ureteral stenosis. However, prior study revealed that 80% of patients experience stent-associated pain when indwelling DJ stents, and 78% of patients experienced urinary dysfunction [11]. The stent also causes stent-related LUTS, which can significantly impact patients’ quality of life. Additionally, prolonged stent duration increases the risk of colonization by multi-drug-resistant flora [12] and forgetting the stent [13]. Therefore, it is of great significance to investigate whether the duration of postoperative stent placement can be shortened to alleviate stent-related discomfort and improve patient’s quality of life. Several studies have demonstrated that in cases of uncomplicated ureteroscopy for distal ureteral stones, long-term stent implantation may not be necessary [14, 15]. However, surgeons prefer the placement of ureteral stents for 1–2 weeks when treating upper urinary tract stones [16]. At present, there is still a lack of studies on the safety of short-term stenting after fURL, especially non-pre-stented fURL.

LUTS were likely associated to the presence of the stent [17]. According to our results, LUTS in the 2-days group showed significantly improvement, particularly regarding hematuria, frequent urination, and pain during urination. In contrast, discomfort persisted for up to 1 week in the 1-week group following stent removal. There was no significant difference in fever between the two groups on POD 7, a finding similar to the meta-analysis on stentless procedures following rigid ureteroscopic lithotripsy by Song et al [4]. Although the 2-days group had a lower VAS score than the 1-week group, the difference was not statistically significant. This observation aligns with previous studies conducted by Hussein and Kenan et al [18, 19].

Shorter stent placement seemed to enhance quality of life. Patients who underwent early stent removal experienced not only milder LUTS but also a faster recovery in terms of returning to normal physical activities and mental health (Fig. 2). Even after the stents of patients in the 1-week group were removed for 5 days, 56.6% of these patients had not fully recovered in terms of light physical activities. Additionally, half of the patients in this group continued to encounter difficulties in resuming normal interpersonal interactions. In contrast, 67.1% of patients in the 2-day group achieved satisfactory recovery by POD 7. a similar trend in USSQ scores has been observed in the study by Christopher et al. [20, 21].

The mean SFR in our study was 82.9%, which closely aligns with Jacob Cohen’s reported SFR of 87% [22]. On average, 60.1% of patients in our study achieved complete stone clearance. Our CSR was slightly higher than the 49.6% reported by Hyung Joon Kim et al. in the real-world setting [23]. Regardless of the diameter size used to assess SFR, there was no significant difference between the two groups. This suggests that the stent duration may not affect the passage of stone fragments.

Currently, most guidelines do not recommend routine pre-stenting. Previous research has indicated that pre-stenting, as compared to non-pre-stenting, results in a significant sevenfold reduction in the risk of severe injury [8]. Some clinical trials related to postoperative stentless procedures included pre-stented patients [3, 5]. Preoperative stents have been shown to prevent ureteral injury and improve the success rate of postoperative stentless procedures. However, it is important to consider that they may increase the patient’s cost and discomfort [17].

Although omitting the use of UAS can reduce ureteral damage, the UAS can be quite beneficial in cases involving large and multiple renal stones [24]. It may be easier to achieve complete stone clearance using a UAS. Traxer and Thomas assessed the incidence and severity of ureteral injury following the placement of 12/14Fr sheaths. According to their findings, 46.5% of cases resulted in ureteral wall injury, and severe damage to the smooth muscle layer was observed in 13% of these cases [8]. They suggested that the higher the grade of ureteral injury, the later the removal time of DJ stents. But one recent meta-article reviewing 3766 studies suggested that there was no direct evidence linking UAS to ureteral injury [25]. Makoto’s study demonstrated that the incidence of ureteral injury above Traxer-grade 2 was only 19.3% when using 11/13Fr sheaths without pre-stenting, and this finding indicated a lower incidence compared to Traxer’s report [26]. In our study, the 11/13Fr UAS were used in all procedures and the incidence of ureteral injury above the Traxer-grade 2 was only about 14%. Non-pre-stented patients using 11/13Fr UAS had a low probability of severe ureteral injury, and most patients could safely have the stents removed early.

Although the guidelines do not recommend the placement of DJ stents after “simple URS”, the standard for stentless procedures remains strict and ambiguous [14]. In fact, urological surgeons around the world perform stentless procedures with varying standards. Arsalan Pervaiz’s study concluded that patients who did not have a severe ureteral injury were suitable for stentless procedures [27]. The study conducted by Christopher et al. only excluded patients with stones over 1.5 cm or true ureteral perforation. However, the unplanned emergency treatment and readmission rates reported in their study were relatively high, reaching up to 21.6% and 8.1%, respectively [20]. Saddam had a similar report of a high emergency rate [17]. The high emergency treatment rate seems to indicate that stentless procedures treatment is not appropriate for most patients. Djaladat came up with that a short period of stent drainage seemed to eliminate the possibility of early ureteral edema, secondary hydronephrosis, and pain [28]. Our results also suggested that short-term stenting can decrease unplanned emergency visits [29]. In certain situations, early stent removal is not recommended: (a) possible postoperative hematoma or perirenal effusion, (b) severe postoperative hematuria, pain or dynamic obstruction due to high-grade ureteral injury, (c) patient’s own concern, (d) presence of large residual stone fragments.

Previously, Bach et al. conducted extensive research. In FAST (Fast track stent study) 1, they used ureter catheters instead of stents for 6 h after URS, and the results showed that short-term stenting with straight catheters led to a better quality of life, similar to our findings [21]. In FAST 2, Bach et al. tried a tubeless procedure for pre-stented patients [30]. Although lower urinary tract symptoms, pain, and health status were improved, the reintervention rate was 10% higher than FAST 1. In FAST 3, they briefly used mono‑J stents for 6 h instead of double J stents, but the study was terminated early due to a high reintervention rate of 32.2% [3]. However, in the FAST series, their treatment didn’t seem to focus adequately on patients’ postoperative conditions. The timing of stent removal should be determined by both intraoperative and postoperative conditions.

As far as we know, this study is the first to specifically investigate the early removal of stents after non-pre-stented fURL. However, as this study is retrospective in nature, further large-scale prospective studies are needed to confirm our conclusion. In addition, we did not analyze the incidence of long-term complications because of the short follow-up period.