Abstract
Objective
This study investigated the effect of preoperative double-J stent placement on stone recurrence following flexible ureteroscopic lithotripsy and analyzed the risk factors for postoperative stone recurrence. The study aimed to provide a clinical reference for better management of the identified risk factors.
Methods
This retrospective study collected data from patients who underwent flexible ureteroscopic lithotripsy for urinary stones between April 2023 and May 2024. Patients were divided into two groups based on whether a double-J stent was placed preoperatively. Comparisons were made between the stent and nonstent groups. Univariate and multivariate logistic regression analyses were performed to identify the risk factors for postoperative stone recurrence.
Results
The recurrence rate was 19.51% in the nonstent group and 1.47% in the stent group, with a statistically significant difference (P = 0.001). Stone removal strategy (P < 0.001), preoperative systolic blood pressure (P = 0.017), and intraoperative blood loss (P = 0.044) were identified as risk factors for postoperative recurrence, with stone removal strategy (P = 0.013) and preoperative systolic blood pressure (P = 0.017) being independent risk factors.
Conclusions
Preoperative placement of a double-J stent is associated with a lower recurrence rate of stones following flexible ureteroscopic lithotripsy than no preoperative stenting. Stone removal strategy and preoperative systolic blood pressure are independent risk factors for stone recurrence following flexible ureteroscopic lithotripsy.
Keywords
Introduction
Urinary stones are extremely common, affecting approximately 10% of the global population, and its incidence is steadily increasing each year.1,2 Apart from obstruction and infections caused by the stones themselves as well as complications associated with surgical interventions, urinary stones increase the risk of chronic kidney disease, coronary heart disease, and mortality.3,4 Currently, treatments for urinary stones are classified into surgical and nonsurgical methods. The main minimally invasive surgical methods include flexible ureteroscopic lithotripsy (FURSL) and percutaneous nephrolithotomy (PCNL). 5
Although PCNL is effective in the treatment of upper urinary tract stones, it is limited by its substantial trauma and high incidence of complications such as bleeding6,7 FURSL may be considered a better treatment modality than PCNL for kidney stones with a diameter of ≤2 cm. 8 Stone removal surgeries such as PCNL and FURSL are associated with the risks of postoperative residual stones and recurrence, warranting subsequent secondary surgery. 9
It is necessary to explore whether preoperative placement of double-J (DJ) stents affects the stone recurrence rate following FURSL. Current studies mainly focus on the impact of preoperative ureteral stent placement on the stone clearance rate, and no study has explored whether preoperative ureteral stent placement affects postoperative stone recurrence. Shields et al. 10 demonstrated that preoperative ureteral stenting is positively correlated with the success rate of minimally invasive stone removal. Jeong et al. 11 also revealed that preoperative ureteral stent placement improved the success rate of ureteral sheath placement, thereby increasing the stone clearance rates. This study investigated the relationship between preoperative ureteral stent placement and postoperative stone recurrence, aiming to clarify whether preoperative ureteral stent placement is conducive to reducing the postoperative stone recurrence rate.
This study analyzed the factors influencing stone recurrence following FURSL to provide reference evidence for clinicians to better manage risk factors, reduce the postoperative recurrence rates, and improve the patient quality of life.
Methods
Study population
A total of 109 patients with kidney and upper ureteral stones underwent FURSL in the Department of Urology at Peking University First Hospital–Miyun Hospital between April 2023 and May 2024. Among them, 41 (37.61%) underwent FURSL without DJ tubes and 68 (62.39%) underwent FURSL with DJ tubes. Clinical and follow-up data were collected. Clinical data included general demographic information, perioperative data, stone diameter, and postoperative stone clearance rates.
The recurrence of stones is defined as the recurrence clearly identified by imaging, that is, no residual stone with a diameter of <3 mm detected by B-ultrasound or computed tomography (CT) within 1 week after the operation as well as new stones being detected on subsequent B-ultrasound or CT. This study considered the recurrence of stones within half a year as the clinical outcome.
The inclusion criteria were as follows: (a) kidney or ureteral stones confirmed by ultrasound, intravenous urography, or CT; (b) single stones; (c) stone diameter ≤2 cm; (d) patients undergoing FURSL; and (e) complete baseline and follow-up data. The exclusion criteria were as follows: (a) coagulopathy and (b) cardiac dysfunction precluding surgery.
This study’s clinical variables included sex, age, body mass index, diabetes, hypertension, coronary heart disease, stone diameter, side (left or right), stone location, stone removal strategy, operative time, intraoperative blood loss, blood pressure, and hematological indicators. Postoperative stone recurrence within 6 months was considered the clinical outcome for exploring the risk factors for stone recurrence after FURSL for kidney and ureteral stones.
FURSL without DJ stent placement refers to a single-session procedure wherein stone removal is completed during one operation. FURSL with preoperative DJ stent placement involves a first-stage procedure to insert the DJ stent, followed by FURSL conducted approximately 2 weeks to 2 months later. For planned nonemergent placement, an F6 silicone tube is used, and FURSL is routinely performed 2 weeks after the placement. The operative time is defined as the duration from the insertion of the ureteroscope into the bladder to the placement of the Foley catheter. Intraoperative blood loss is defined as the total volume of blood and irrigation fluid collected in the suction bottle minus the volume of irrigation fluid. Hospitalization duration refers to the total number of days from admission to discharge, including both the preoperative and postoperative periods.
This study was conducted in accordance with the principles of the Declaration of Helsinki (2024 revision) and was approved by the Ethics Committee of Peking University First Hospital–Miyun Hospital (NO.: 2021-04). The need for informed consent was waived for this retrospective analysis. The data presented in this study have been de-identified to remove information that could identify patients.
Surgical technique
The surgeon in this study was a physician with over 20 years of experience in urolithiasis surgery and had performed hundreds of urolithiasis-related procedures. The patient was placed in the lithotomy position under successful anesthesia. Routine disinfection and draping were performed. A 12-F urethral catheter was inserted to drain urine, and a F9.5 flexible ureteroscope was introduced via the urethra into the bladder to inspect and locate the affected ureteral orifice. After inserting a nitinol guidewire, the ureteroscope was withdrawn, and a 12-F hydrophilic access sheath was placed along the guidewire. The ureter and renal pelvis/calyces were inspected. Stones were fragmented using a Holmium laser (1 J, 20 W), and some fragments were extracted with an NGage basket. Powdered fragments were left to pass naturally. After confirming that there were no residual stones with a diameter >2 mm, a DJ stent was placed, and the procedure was concluded.
Statistical analysis
SPSS 22.0 was used for statistical analysis. Normally distributed data were expressed as mean ± standard deviation, while non-normally distributed data were described using median (range). For continuous variables, unpaired t-tests were used for normally distributed data, and the Mann–Whitney U test was used for non-normally distributed data. Fisher’s exact test was used for categorical variables. Univariate and multivariate binary logistic regression analyses (P < 0.05) were performed to identify independent risk factors for stone recurrence following FURSL.
Results
Baseline data
Baseline data of the patients undergoing FURSL are shown in Table 1. A total of 109 patients underwent FURSL for kidney and ureteral stones, with an average age of 52.09 ± 12.53 years. The mean stone diameter was 1.16 ± 0.31 cm. The proportion of patients undergoing FURSL without preoperative DJ stent placement was 37.61% (41/109), while the proportion of those undergoing FURSL with preoperative DJ stent placement was 62.39% (68/109). The overall stone recurrence rate was 8.26% (9/109).
Basic characteristics of the patients.
BMI: body mass index; CHD: coronary heart disease; DJ: double-J.
Comparison of the patients with and without preoperative DJ stent placement
The clinical data of the patients in the preoperative DJ tube group and nonpreoperative DJ tube group are shown in Table 2. The stone recurrence rates in the preoperative and nonpreoperative DJ tube groups were 1.47% (1/68) and 19.51% (8/41), respectively, with a statistically significant difference (P = 0.001). The average ages of the patients in the preoperative and nonpreoperative DJ tube groups were 54.79 ±11.72 and 47.61 ± 12.69 years, respectively, with a statistically significant difference (P = 0.003).
Comparison of stone removal using flexible ureteroscopy between the preoperative and nonpreoperative DJ tube groups.
BMI: body mass index; CHD: coronary heart disease; DJ: double-J.
Analysis of risk factors for stone recurrence following FURSL
The clinical data of the recurrence and nonrecurrence groups are shown in Table 3. The proportions of DJ tube retained before surgery in the recurrence and nonrecurrence groups were 11.11% (1/9) and 67% (67/100), respectively, with a statistically significant difference between the two groups (P = 0.001).
Comparison of stone removal using flexible ureteroscopy between the recurrence and nonrecurrence groups.
BMI: body mass index; CHD: coronary heart disease; DJ: double-J.
The preoperative systolic blood pressure levels were 120.89 ± 5.26 and 127.87 ± 8.50 mmHg in the recurrence and nonrecurrence groups, respectively, with a statistically significant difference between the two groups (P = 0.017). The intraoperative blood losses were 10.33 ± 15.33 and 4.00 ± 6.06 mL in the recurrence and nonrecurrence groups, respectively, with a statistically significant difference between the two groups (P = 0.013).
Univariate regression analysis identified stone removal strategy (P < 0.001), preoperative systolic blood pressure (P = 0.017), and intraoperative blood loss (P = 0.044) as risk factors for recurrence. Multivariate regression analysis confirmed stone removal strategy (P = 0.013) and preoperative systolic blood pressure (P = 0.017) as independent risk factors (Table 4).
Univariate and multivariate regression analyses of the recurrence of kidney and ureteral stones treated with flexible ureteroscopy.
BMI: body mass index; HR: hazard ratio; CI: confidence interval.
Discussion
Urinary stone disease is one of the most common diseases of the urinary system, with an incidence of 5%–10% in China, which has been gradually increasing. 12 FURSL is widely used owing to its minimal invasiveness, high efficiency, and broad indications, and it has become the treatment of choice for kidney stones with a diameter of 1–2 cm in patients who cannot undergo PCNL. 13 Several studies have shown that preoperative DJ stent placement can improve the stone clearance rate through FURSL and reduce the risk of systemic inflammatory response syndrome.10,11,14
Currently, the mainstream treatment methods for urinary stones include PCNL and FURSL. Extracorporeal shock wave lithotripsy (ESWL) plays a key role in the management of urinary tract stones. Although ESWL is considered the only noninvasive treatment, it is less effective for larger stones (generally >2 cm) compared with other methods, requiring multiple sessions and often causing complications such as pain and hematuria during the process.15,16 PCNL is more efficient in cases of large (>2 cm) or complex stones. It not only removes stones but also helps protect renal function in patients with chronic kidney disease. However, PCNL requires higher technical skill and is more invasive. For stones smaller than 2 cm, FURSL may have more advantages. With its low incidence of postoperative complications and low cost, FURSL has surpassed both ESWL and PCNL and emerged as the mainstream method for treating kidney and urinary tract stones. Although FURSL is an advanced surgical technique, further improvement is warranted in certain areas.
It remains controversial whether preoperative DJ stent placement affects stone recurrence after FURSL. DJ stents play an important role in the treatment of kidney stones, ureteral stones, and benign tumors of the kidney and ureter. Preoperative DJ stent placement can expand the ureter to facilitate stone removal, preventing damage to the ureter during the procedure and reducing postoperative complications such as infections and ureteral obstruction. Many surgeries are affected by limited visibility during the procedure, and placing a DJ stent preoperatively can help expand the ureter, improve visibility, and enhance the convenience of the procedure. This also reduces the occurrence of ureteral strictures, allowing better access for surgical instruments, thereby improving the efficiency of the surgery. Preoperative DJ stent placement has shown advantages in improving the postoperative quality of life and increasing the success rate of surgery, as it can effectively prevent the retention of stone fragments in the ureter, promoting their smooth elimination due to the expanded ureter and reducing the likelihood of requiring a second surgery.17–21
DJ stents are an important tool in urology; however, certain complications, such as displacement, hematuria, and infections, have been reported with their widespread use. Geavlete et al. 22 retrospectively analyzed 50,000 surgeries performed on 36,688 patients between 1996 and 2021. They reported 41,369 complications, including 153 cases (0.3%) of stent misplacement, 779 cases (1.6%) of stent displacement (427 of which were proximal and 352 were distal), 5213 cases (10.4%) of hematuria, and 7436 cases (14.9%) of urinary tract infections. Additionally, Altay et al. 23 reported a case of renal parenchymal perforation caused by DJ stent placement after ureteroscopic surgery, alongside other adverse reactions associated with stent placement. Preoperative DJ stent placement may lead to local irritation and mild damage to the ureteral mucosa, which can disrupt the integrity of the epithelial cells and induce an inflammatory response. This creates a microenvironment that is more favorable for stone adhesion. Furthermore, bacteria tend to colonize the stent surface, forming biofilms over time. The bacteria within the biofilms metabolize and produce urea nitrogen, which alkalinizes the urine. In an alkaline environment, calcium phosphate crystals are more likely to accumulate and form stones.24–26
This study did not explore the complications arising from DJ stent placement but focused on analyzing the impact of preoperative DJ stent placement on stone recurrence after FURSL. Our findings suggest that preoperative DJ stent placement is beneficial in reducing the recurrence of stones after surgery. We hypothesize that the stent helps maintain urinary tract patency, relieves obstruction, reduces postoperative urinary retention, lowers the risk of urinary tract infections and inflammation, and promotes the expulsion of stone fragments. Additionally, the stent helps prevent postoperative ureteral stricture or scarring, particularly after large or complex stone surgeries, reducing the likelihood of recurrence.
In this study, we found that preoperative systolic blood pressure is a risk factor for stone recurrence following FURSL. High preoperative systolic blood pressure is partly attributed to preoperative anxiety and chronic hypertension. Even without a formal diagnosis of hypertension, elevated systolic blood pressure indicates metabolic and renal function imbalance, increasing the risk of stone recurrence through changes in renal blood flow, metabolic disturbances, oxidative stress, and inflammation. Zhou et al. 27 conducted a study that demonstrated an association between the recurrence of ureteral stones and metabolic syndrome, such as high systolic blood pressure. The possible mechanism is the alteration of renal hemodynamics, which increases renal perfusion pressure, leading to increased glomerular pressure and damage to the glomerular filtration barrier. This change can affect the urine composition, leading to increased excretion of substances such as calcium and oxalate, which increases the risk of stone formation.28,29 Patients with elevated preoperative systolic blood pressure should undergo strict preoperative metabolic evaluation and postoperative follow-up, with adjustments to diet and lifestyle, for treating potential metabolic disorders and reducing stone recurrence.
We also identified intraoperative blood loss as a risk factor for stone recurrence in the univariate analysis. Blood loss may lead to insufficient local renal blood supply, impairing renal function and disrupting the kidney’s ability to regulate urine composition, leading to higher concentrations of stone-forming substances (such as calcium, oxalate, and uric acid) and increasing the risk of stone recurrence.
Previous studies have suggested that diabetes is a significant factor influencing stone recurrence after surgery, but no such relationship was found in this study. Diabetes affects the kidneys in multiple ways, i.e. through the glomerulus, renal tubules, or urinary system.30,31 Papachristoforou et al. 32 described how prolonged hyperglycemia can induce oxidative stress and inflammation through NF-kB-mediated pathways, directly damaging renal structures. This study did not find a significant correlation between diabetes and stone recurrence, which may be attributed to the limited sample size and follow-up period.
Our study has several limitations. First, it is a single-center study, and the limited sample size may have introduced bias in the results. Second, this study used a retrospective analysis approach, and all factors influencing stone recurrence after FURSL may not have been included in the data collection process, particularly variables highly correlated with stone recurrence, such as stone composition and metabolic evaluation data. Prospective studies are warranted in the future to incorporate key variables such as stone composition, metabolic evaluation data, and renal function while increasing the sample size.
Conclusion
Preoperative DJ stent placement significantly reduces stone recurrence after FURSL compared with no stent placement. Stone removal strategy and preoperative systolic blood pressure are independent risk factors for stone recurrence after FURSL.
Footnotes
Acknowledgment
None.
Author contributions
Conception and design: Chao Zuo, Yue Li, Yaming Gu Administrative support: Chao Zuo, Yue Li, Yaming Gu Provision of study materials or patients: Chao Zuo, Yue Li, Zihui Gao, Yaming Gu Collection and assembly of data: Chao Zuo Data analysis and interpretation: Chao Zuo Manuscript writing: All authors Final approval of the manuscript: All authors
Consent to participate
The need for informed consent was waived due to the retrospective design of the study.
Data availability
The datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request.
Declaration of conflicting interests
None declared.
Ethical approval
The trial was conducted in accordance with the Declaration of Helsinki (as revised in 2013). This study was approved by the Ethics Committee of Peking University First Hospital–Miyun Hospital (NO.: 2021-04).
Funding
None.
