Evaluation of postoperative safety and comfort of ureteral stent removal with extraction string in modified split-leg prone percutaneous nephrolithotomy (2025)

Objective

To evaluate the safety and comfort of ureteral stents with extraction strings during modified split-leg prone percutaneous nephrolithotomy (PCNL).

Methods

A prospective, single-centre study was conducted on 100 patients undergoing PCNL for unilateral upper urinary tract stones from April to August 2024. Patients were randomized into two groups: 50 with extraction-string stents and 50 without. Standardized surgical and postoperative protocols were followed. Primary outcomes included pain scores during stent removal, incidence of hematuria and flank pain, stent indwelling time, and cost analysis. Statistical analysis was performed using GraphPad Prism 9.5.0.

Results

The extraction-string group demonstrated significantly lower pain scores during stent removal (0.86 ± 0.62 vs. 5.23 ± 1.74, p < 0.05) and shorter stent indwelling time (16.06 ± 4.48 vs. 60.54 ± 20.4 days, p < 0.05). The incidence of hematuria (8 vs. 29 cases) and flank pain (7 vs. 22 cases) was notably lower in the extraction-string group (p < 0.05). Additionally, each patient in this group saved an average of 1,065 Yuan (145.78 USD) by avoiding cystoscopic removal. No significant differences were observed in postoperative hospitalization days or urinary irritation symptoms (p > 0.05).

Conclusion

The use of extraction-string ureteral stents during modified split-leg prone PCNL significantly reduces stent removal pain, enhances procedural convenience, lowers economic burden, and maintains a safety profile comparable to traditional methods. This innovative technique represents a clinically valuable advancement in PCNL surgery.

Study design and participants

A prospective study was conducted involving 100 patients undergoing PCNL for unilateral upper urinary tract stones from April to August 2024 in the Urology Department of the First Affiliated Hospital of Sun Yat-sen University. The sample size was calculated based on a two-sided significance level (α) of 0.05 and a study power of 90%. A preliminary pilot study suggested a difference in the mean visual analog pain score between the control and experimental groups (5 vs. 1 point, respectively), with an estimated standard deviation of 2. Considering a 10% dropout rate, the adjusted sample size for each group was calculated to be sufficient to ensure statistical robustness. Participants were equally randomized into an extraction string group and a control group, with each group having 50 participants. The inclusion criteria required that the stone clearance surgery be performed in a single session without the need for any secondary operations. The exclusion criteria included patients who could not return for stent removal, those who were pregnant, individuals undergoing bilateral surgery, or patients requiring multiple stents. All participants adhered to the follow-up protocol and returned to our department for stent removal as planned. The study protocol adhered to the 2013 revision of the Declaration of Helsinki and was approved by the Ethics Committee of the First Affiliated Hospital of Sun Yat-sen University.

Surgical technique

Under general anesthesia, patients were positioned in a modified split-leg prone position, and both the lumbar and perineum areas were disinfected (Fig.1A). A 16Fr silicone Foley catheter was inserted into the bladder to guide the ureteroscope under this prone position because a catheter without a balloon would easily slip out of the urethra, and it might be difficult without guidance for the surgeon to get into the bladder in this position. A 9.8 Fr ureteroscope was advanced alongside a Foley catheter to identify the target ureteral orifice. Without the modified prone position, which was lifting the contralateral leg, sometimes, it was hard for the male patient to find the ureter orifice because of the enlarged prostate. Subsequently, a 5 Fr ureteral catheter was inserted approximately 25cm into the ureter to create artificial hydronephrosis to help the ultrasound-guided puncture. Our department didn’t perform the fluoroscopy, and this ureteral catheter would guide stent placement after the completion of lithotripsy (Fig.1B). Ultrasound-guided renal access was established, and an 18–20 Fr percutaneous working tract was created to perform stone fragmentation using a nephroscope. After the complete removal of the stones, the tip of the ureteral catheter was pulled out from the percutaneous nephrostomy tract and cut off. A guide wire was then inserted into the catheter from the renal working tract end and pulled out through the urethral orifice end. Following this, a 6Fr ureteral stent was inserted over the guide wire in a retrograde manner through the urethra, and another look by the 9.8 Fr ureteroscope through the urethra would confirm the position of the coiling of the bladder end of the stent (Fig.1C). The extraction string was secured externally. In female patients, it was attached to the lower abdomen. In male patients, the string was secured to the penile shaft (Fig.1D). A nephrostomy tube was placed and removed on postoperative day 3 following radiographic confirmation of stone clearance. After two weeks, the stent was removed in the outpatient clinic by gently pulling the extraction string for the extraction string group. The control group received traditional standard antegrade stent placement requiring cystoscopic removal, while other processes were the same as the trial group. The stents were removed by a rigid cystoscope for the control group. According to the clinical resources of our outpatient operation room, the cystoscope would usually be scheduled 4–6 weeks after discharge. Both groups received postoperative α-blockers and antispasmodics.

Outcome measures

During the stenting period, we monitored symptoms such as urinary tract irritation, hematuria, fever, accidental stent dislodgement, flank pain, and emergency visits. Overall health status and work status are assessed by the Likert scale. Immediately after removing the stent, we evaluated patients for pain using the Visual Analog Scale (VAS) to measure the pain associated with the extraction.

Statistical analysis

Statistical analysis was conducted using GraphPad Prism 9.5.0. Continuous variables were compared using independent t-tests; categorical variables were analyzed with χ² or Fisher’s exact tests. p < 0.05 considered statistically significant.

There were no significant differences in baseline characteristics such as age, gender, BMI, operative side, stone location, and the maximum stone diameter between the two groups (P > 0.05) (Table1).

The pain score for stent removal in the extraction string group was significantly lower than that of the control group undergoing cystoscopic removal (0.86 ± 0.62 vs. 5.23 ± 1.74, P < 0.05). The stent indwelling time was significantly shorter in the extraction string group (16.06 ± 4.48 days vs. 60.54 ± 20.4 days, P < 0.05). The incidence of hematuria (16% vs. 58%) and flank pain (14% vs. 44%) in the extraction string group was also lower than in the control group (P < 0.01). According to the hospital’s fee standards, patients in the extraction string group saved 1,065 Yuan (145.78 Dollars) per person in cystoscopic removal costs. There were no significant differences between the extraction string and control groups in terms of postoperative hospital stay (4.50 ± 2.48 days vs. 4.62 ± 2.50 days), the occurrence of urinary tract irritation symptoms during stenting (33 cases vs. 32 cases), or stent dislodgement after surgery (3 cases vs. 0 cases) (P > 0.05) (Table2).

Both groups had no postoperative complications, such as sepsis or bleeding, and no stent-related complications, such as fever or emergency visits, during the follow-up period. Patients in both groups reported no significant impact on general condition or work status due to the stent during follow-up.

The duration, placement, and removal of ureteral stents and their impact on patient’s quality of life have long been topics of interest in urology, with numerous studies highlighting the associated morbidity and discomfort [8]. Besides using extraction strings, other techniques for stent retrieval have been explored. Using a magnetic catheter to remove the ureteral stent demonstrated reduced pain during removal and improved patient-centered outcomes [9]. However, its application was limited due to the need for specialized stents and catheters. Traditionally, ureteral stents with extraction strings have primarily been used in retrograde ureteroscopy, where they have been shown to reduce the pain of stent removal without increasing the risk of infection, urinary tract irritation, or stent-related complications [10, 11]. These findings align with our clinical data. However, we are the first study to introduce commercially available extraction string stents that don’t need any special preparations in PCNL, making it an innovative attempt.

This investigation provides empirical evidence that the application of ureteral stents with extraction strings during PCNL in the modified split-leg prone position confers significant clinical benefits, including a marked reduction in pain during stent extraction and an enhanced procedural efficiency in stent removal. The new technique is the key of the investigation and some of the details of the technique must be emphasized. First of all, we are the first to illustrate a technique that does not need to make any changes to the stent to leave an extraction string during a PCNL procedure. Qi et al. have also explored the feasibility of placing suture stents in PCNL [12]; However, their study utilized a conventional prone position and complex method, requiring modifications to the stent. We successfully placed commercially available extraction string stents by simply adopting the modified split-leg prone position and employing an endoscopic combined intrarenal surgery approach. This method is simple, reproducible, and easy to perform. The modification of elevating the contralateral leg on the operative side is of critical importance. In elderly male patients with benign prostatic hyperplasia or female patients with uterine prolapse, the ureteroscope often requires a significant angulation to visualize the ureteral orifice adequately. In such cases, the thigh may obstruct the ureteroscope unless the leg is appropriately elevated. We employ a Foley catheter (14-16Fr) rather than an 8Fr conventional catheter for two primary reasons. Firstly, in this modified position, the 8Fr catheter—typically used for guidance and drainage—lacks a balloon and is prone to dislodgement. Secondly, in this inverted position, navigating the ureteroscope into the bladder, particularly in male patients, presents a considerable challenge due to the elongated urethra and its anatomical curvatures. By utilizing a balloon catheter, this issue is effectively mitigated, as the balloon traction straightens the urethral curves and provides a definitive guide for the ureteroscope to follow.

Patients in the extraction string group reported significantly lower stent extraction pain scores than the control group, and their stent removal time was notably shorter. In our clinic, stent retrieval is typically performed using a rigid cystoscope, which can cause considerable discomfort for patients under local anesthesia, particularly for male patients, due to the anatomical complexity of the male urethra [13]. In contrast, patients in the non-extraction string group often face prolonged scheduling delays, typically waiting 4–6 weeks for removal due to limited surgical resources available on operation days. Conversely, most extraction string patients can return to the clinic for straightforward stent removal, significantly reducing both waiting times and the risk of forgotten stents [14]. Cystoscopic stent removal, which requires scheduling and competes for limited outpatient surgical resources, often results in significant delays. These delays may increase the risk of stent-related complications, such as infections and hematuria [15]. Our study also identified significant differences in the incidence of hematuria and low back pain between the two groups, with lower rates observed in the extraction string group, suggesting a potential advantage in reducing postoperative complications. To assess patient comfort during stent removal, we employed the Visual Analog Scale (VAS), a widely validated tool for quantifying postoperative pain in urological procedures. Unlike conventional questionnaire surveys that primarily focus on patient anxiety and procedural fear, our evaluation directly addressed the core issue of pain during stent removal [16, 17]. The statistically significant difference in pain scores between the two groups underscores the efficacy of the extraction string technique. Notably, some patients in the extraction string group reported a completely painless stent removal experience during follow-up, further reinforcing the clinical utility of this approach. Among the few complications reported, three female patients in the extraction string group experienced urine leakage. Upon evaluation, these cases were attributed to stent dislodgment. Importantly, the stents had been in place for at least five days, allowing for safe removal without additional complications [18].

The economic benefits associated with using extraction string stents are also noteworthy. By eliminating the need for cystoscopic removal, patients in the extraction string group saved an average of 1,065 Yuan (approximately 145.78 USD) in medical expenses per individual. This reduction in costs not only alleviates financial burdens for patients but also optimizes hospital resource allocation, thereby enhancing overall healthcare efficiency [19].

This study has several limitations, including a small sample size, single-center design, and short follow-up duration, which may limit the generalizability of the findings. Future research should focus on conducting larger, multi-center, long-term randomized controlled trials to address these limitations and further validate the benefits of ureteral stents with extraction strings. Moreover, the applicability of this technique in more complex cases, such as bilateral stones or patients requiring multiple stents, should be explored. Future studies should also include patient-reported outcomes beyond pain—such as anxiety and quality of life—evaluate the cost-effectiveness of the technique (including indirect costs), and compare it with emerging methods like magnetic stents. By tackling these issues, future research can provide a more comprehensive understanding of this innovative technique and its role in optimizing urological care.

PCNL:

percutaneous nephrolithotomy VAS = Visual Analog Scale

Authors and Affiliations

1. Department of Urology, The First Affiliated Hospital of Sun Yat-sen University, 58 Zhongshan Second Road, Guangzhou, 510080, Guangdong, China

   Shuangjian Jiang,Junlong Zhang,Yukun Wu,Chengqiang Mo&Rongpei Wu

Contributions

Jiang Shuangjian and Wu Rongpei were responsible for surgical procedures and manuscript writing. Zhang Junlong and Wu Yukun were responsible for data collection and statistical analysis. Mo Chengqiang was responsible for study supervision and manuscript revision. All authors reviewed the manuscript.

Corresponding author

Correspondence to Rongpei Wu.

Ethics approval and consent to participate

All procedures performed in studies involving human participants were in accordance with Clinical Research and Animal Trials of the First Affiliated Hospital of Sun Yat-sen University (IRB approval number [2025]066) and with the 2013 Helsinki Declaration and its later amendments or comparable ethical standards. This article does not contain any studies with animals performed by any of the authors. All the participants of the study signed a written informed consent.

Consent for publication

Written informed consent was obtained from the patient for publication and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Competing interests

The authors declare no competing interests.

Clinical Trial Number

Not applicable.

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