Abstract
Both shock wave lithotripsy (SWL) and flexible ureterorenoscopy (F-URS) are recommended as the first choice for non-lower pole kidney stones. Therefore, we conducted a prospective study to evaluate the efficacy, safety, and cost of SWL versus F-URS in patients with solitary non-lower pole kidney stones ≤ 20 mm under the COVID-19 pandemic. This prospective study was conducted in a tertiary hospital from June 2020 to April 2022. Patients who underwent lithotripsy (SWL or F-URS) for non-lower pole kidney stones were enrolled in this study. The stone-free rate (SFR), retreatment rate, complications, and cost were recorded. Propensity score-matched (PSM) analysis was performed. A total of 699 patients were finally included, of which 81.3% (568) were treated with SWL and 18.7% (131) underwent F-URS. After PSM, SWL showed equivalent SFR (87.9% vs. 91.1%, P = 0.323), retreatment rate (8.6% vs. 4.8%, P = 0.169), and adjunctive procedure (2.6% vs. 4.9%, P = 0.385) compared with F-URS. Complications were scarce and also comparable between SWL and F-URS (6.0% vs 7.7%, P > 0.05), while the incidence of ureteral perforation was higher in the F-URS group compared with the SWL group (1.5% vs 0%, P = 0.008). The hospital stay was significantly shorter (1 day vs 2 days, P < 0.001), and the cost was considerably less (1200 vs 30,083, P < 0.001) in the SWL group compared with the F-URS group. This prospective cohort demonstrated that SWL had equivalent efficacy with more safety and cost benefits than F-URS in treating patients with solitary non–lower pole kidney stones ≤ 20 mm. During the COVID-19 pandemic, SWL may have benefits in preserving hospital resources and limiting opportunity for virus transmission, compared to URS. These findings may guide clinical practice.
Keywords: Kidney stone, COVID-19, Extracorporeal shock wave lithotripsy, Flexible ureterorenoscopy, Propensity score-matched
Introduction
The prevalence of urolithiasis ranges from 1 to 20% worldwide; depending on variations in ethnic, genetic, climatic, geographical factors, and dietary patterns, about 50% of patients experienced at least one recurrence during their lifetime [1]. Urolithiasis is commonly accompanied by significant complications, including colic episodes, urinary tract infection, nausea and vomiting, hydronephrosis, and even impairment of renal function [2]. It can be observed throughout the urinary tract, but the kidney is the most common location for urolithiasis [3].
Although kidney stones are often asymptomatic in the initial stages, active intervention is frequently performed in the case of stone growth, associated infections, renal colic, and de novo obstruction. Treatment for kidney stones should ideally achieve high stone-free rates and low complication rates. Flexible ureterorenoscopy (F-URS) and extracorporeal shock wave lithotripsy (SWL) are currently the most common treatment options for kidney stones ≤ 20 mm, and is recommended by both the American Urological Association and the European Association of Urology (EAU) guidelines as first-line interventions [4, 5]. F-URS emerged with the advantages of direct visualization, fragmentation, and extraction of kidney stones. With the simultaneous advances in F-URS and holmium laser, it has become a widely accepted option for the management of kidney stones, showing a higher success rate and lower retreatment rate, but includes disadvantages such as invasiveness, need for anesthesia, high cost, and need of expensive instruments and maintenance, especially during the learning curve [6]. SWL has the advantages of non-invasiveness, low complication rate, no anesthesia requirement, and a high level of patient acceptance. However, the effectiveness could be affected by several factors, such as stone size, density, composition, anatomical factors, body habitus of patients, and obesity. Therefore, it may associate with a lower stone-free rate (SFR) and higher retreatment rate [7].
The coronavirus disease 2019 (COVID-19) pandemic has presented urologists with previously unknown difficulties. Along with social restrictions, lockdowns, and entire hospitals were turned into treatment facilities for COVID-19-infected patients, surgical activity had to be reduced. SWL is a good option for patients with stone disease because it does not need anesthesia or intubation, which significantly increases the risk of transmission, requires no hospital stay, and is associated with less emergency room visits than ureteroscopy [8].
The EAU guidelines distinguish between the lower pole (LPS) and non-lower pole kidney stones; it indicated that performing SWL for LPS would be less successful and require multiple sessions and auxiliary procedures [9]. Although the disintegration efficacy of SWL is not limited compared to other locations, the fragments often remain in the calyx and cause recurrent stone formation [10]. However, evidence regarding the optimal modality of non-lower pole kidney stones is scarce. There are only two retrospective studies that included non-lower pole kidney stones. In a retrospective cohort of 99 patients with 10–20 mm renal pelvis stones, both the SFR and complications were equivalent between F-URS and SWL groups, performed by electrohydraulic lithotripter under fluoroscopic guidance [3]. In another retrospective study including 174 patients with radiopaque solitary upper or mid renal calyx stones of 10–20 mm, Cecen et al. [11] indicated that F-URS and SWL have similar treatment outcomes in stone-free, retreatment rate, and complications. The small sample size, the nature of the retrospective study design, and patient selection criteria limit the validity of these studies. Thus, the available evidence failed to conclude a reliable recommendation regarding non-lower pole kidney stones treatment. Therefore, we conducted a prospective study aiming to evaluate the effectiveness, safety, and cost of SWL compared to F-URS in patients with solitary non-lower pole kidney stones ≤ 20 mm.
Methods
Study design
This prospective study was conducted at Shengjing Hospital of China Medical University from June 2020 to April 2022. Shengjing Hospital is a tertiary hospital and is the third-largest hospital in China. A total of 835 patients who underwent lithotripsy (SWL or F-URS) for non-lower pole kidney stones were enrolled in the present study. Finally, there were 699 patients included. Five hundred sixty-eight patients were treated with SWL, and 131 patients were treated with F-URS, Fig. 1.
Fig. 1.
Flowchart of the study. SWL extracorporeal shock wave lithotripsy, F-URS flexible ureterorenoscopy
Ethical approval (No. 2020PS520K) was provided by the Ethics Committee of Shengjing Hospital Affiliated China Medical University on 9 June 2020. Informed consent from all eligible subjects was obtained. The clinical research registry UIN is ChiCTR2000033790. The study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki.
Inclusion and exclusion criteria
Inclusion criteria: stones with a low likelihood of spontaneous passage, persistent pain despite adequate analgesic medication; persistent obstruction, stone growth, or infection; stones located in the renal pelvis (including pelvic-ureteral junction), upper or middle calyx, stone size between 6 and 20 mm, age ≥ 18 years, body mass index (BMI) < 30 kg/m2, ureter stone density ≤ 1000 Hounsfield’s units (HU), and skin to a stone distance less than 11 cm. Recurrent or first-time stone formers were both eligible; Patients with a previous history of urinary stones were only included if they were stone-free for at least 12 months.
Exclusion criteria: pregnancy, coagulopathy, uncontrolled urinary tract infection, severe skeletal malformations, which prevent targeting of the stone; arterial aneurysm in the vicinity of the stone, multiple kidney stones, anatomical obstruction distal to the stone, or congenital urinary anomaly (such as horseshoe kidney or ileal conduit), patients with JJ-stent/nephrostomy insertion before treatment for the resolution of urinary tract obstruction, transplanted kidney, solitary kidney, renal insufficiency (elevated creatinine); stones located in the diverticular neck or a diverticulum.
Decision-making process: patients were given a choice to undergo either F-URS or SWL after counseling them about the advantages and drawbacks of both procedures (such as stone-free rates, costs, hospital duration, and complications). After receiving the explanation, the patients selected the method they preferred. After the patients provided informed consent, the chosen procedure was performed by experienced senior doctors.
The surgical technique of shock wave lithotripsy (SWL)
Extracorporeal shock wave lithotripsy was performed using a third-generation electromagnetic lithotripter (XYS.SUI-6B, Shenzhen New Element Medical Equipment Technology Development Co., Ltd, Shenzhen, China). The focal depth was 110 mm; the focal area was 7 mm (radial) and 45–50 mm (axial), and the focal pressure was 6–30 MPa). The procedure was performed in a supine or prone position without anesthesia. Stone localization and simultaneous real-time monitoring during the process were performed by ultrasound (DC40, Shenzhen Mindray Bio-Medical Electronics Co., Ltd, Shenzhen, China). The shock frequency was 60–90 (shock waves/min). The total number of shock waves applied for one session was between 1500 and 2500 waves, or the session was stopped at a significant stone fragmentation was detected. The voltage applied per session ranged from 10 to 16 kV with stepwise power ramping strategy. All procedures in the SWL group were outpatient procedures.
Before the procedure, careful control of pain for limiting pain-induced movements and excessive respiratory excursions was needed if necessary (suffer from renal colic before SWL). For instance, the VAS score was more than 4, and the patients asked for pain relief; Patients received nonsteroidal anti-inflammatory (e.g., flurbiprofen 50 mg or ketorolac 30 mg by intravenous injection) or opioid drugs (pethidine 50 mg by intramuscular injection) for pain control before SWL. Antibiotic prophylaxis was applied in the presence of increased bacterial burden (infectious stones or bacteriuria). A mild laxative was taken before the procedure if it was difficult to locate the stone due to bowel interference. After the procedure, all patients were instructed to drink fluids and increase physical activity; After SWL, all patients prescribed ɑ-blockers once daily for 1 week.
The surgical technique of retrograde intrarenal surgery (F-URS)
F-URS were performed under general anesthesia in the lithotomy position. After 8/9.8 Fr rigid ureteroscope (Karl Storz, Tuttlingen, Germany) was used, followed by the introduction of 12 /14 Fr or 11/13 Fr hydrophilic-coated ureteral access sheaths through guidewire. Then a 7.5 F flexible ureteroscope (URF-P5, OLYMPUS, Japan) or Single-Use Video Endoscopy (Guangzhou Ruipai Medical Devices, China.) was inserted. The disintegration of the stone was performed using holmium: YAG laser (Lumenis PowerSuite 60w), with a 200 μm laser fiber (energy output of 1–1.5 J at 10–15 Hz was changed according to the stone hardness and efficacy) and “Pop Corn” strategies. Fragments were extracted by forceps or nitinol baskets (Ngage, Cook Incorporated, USA). Irrigation was performed using a pressure-controlled combined irrigation/suction pump (Uromat; Karl Storz, Culver City, CA, USA) with pressure levels ranging from 100 to 200 mmHg. A 5 Fr JJ stent were routinely placed in complicated cases after URS (e.g., ureteral trauma, residual fragments, bleeding, or perforation). A ureteral catheter with a shorter indwelling time (1 day) after uncomplicated URS may also be used.
AJJ stent was inserted if ureteral access failed, followed by URS. A second F-URS procedure was planned after 7–14 days. All of the patients in the group were given intravenous antibiotics for prophylaxis 1 h preoperatively and then continued for the next 24 h, after which they were switched to use oral antibiotics for 3–5 days. The JJ stent was removed 2 weeks after F-URS under local anesthesia using a flexible cystoscope. Alpha-blockers were also applied to reduce stent-related symptoms and colic episodes.
Measurement of characteristics and follow-up
Patient demographics (age, gender, and body mass index [BMI]), comorbidity (hypertension, Diabetes Mellitus, and coronary Heart Disease), Previous history of urinary stone treatment, stone characteristics (stone location, side, size, Hounsfield unit of stone, and grade of hydronephrosis), treatment outcome (operative time, stone-free rate (SFR) after procedure at 1 month, retreatment and adjunctive procedure rate), complications (Clavien–Dindo classification, systemic inflammatory response syndrome [SIRS] [12], sepsis, steinstrasse, renal colic need analgesic requirement, renal hematoma, ureteral injuries such as avulsion or perforation), length of hospital stay and mean costs (USD/$: dollar).
The degree of hydronephrosis was assessed using a CT scan and was categorized as grade 0–4. The kidney without calyx or pelvic dilation were classified as grade 0, with pelvic dilation only were classified as grade 1, accompanying mild calyx dilation were classified as grade 2, severe calyx dilation was grade 3, and those with calyx dilation accompanied by renal parenchyma atrophy were classified as grade 4. Mean CT attenuation value in Hounsfield units. The size of the stone was indicated as the largest diameter of the stone measured by computed tomography (CT). The stone-free rate (SFR) was defined as no evidence of clinically significant stone fragments (≥ 4 mm in size) in combination with a plain X-ray of the urinary tract (KUB) and urinary ultrasound one month after SWL or F-URS. The complete stone-free rate (SFR) was defined as no evidence of any stone fragments in combination with a plain X-ray of the urinary tract (KUB) and urinary ultrasound one month after SWL or F-URS. Retreatment was defined as any subsequent intervention performed for the residual stones beyond the initial preplanned modality. For F-URS, include more than one F-URS session or need for a secondary intervention (e.g., percutaneous nephrolithotomy [PCNL] or SWL). For SWL, include more than one SWL session or need for a secondary intervention (e.g., F-URS or PCNL). Adjunctive procedures were defined as procedures needed to deal with a postoperative complication of the primary treatment (e.g., JJ stent or nephrostomy placement). Perioperative complications were assessed up to one month after treatment using the Clavien-Dindo classification [13]. Calculation of costs included initial treatment costs (including disposables, etc.), retreatment costs, emergency visits costs, and treatment of complications costs.
Follow-up
Postprocedural follow-up visits were performed one month after the procedure to see if any fragment larger than 4 mm was still left in the urinary tract, combined with plain X-ray KUB and urinary ultrasound.
Outcome and sample size calculation
The primary outcome was the evaluation of SFR one month after treatment. The secondary outcome measures were retreatment and adjunctive procedure rate, complications, and cost data. Type I error α was 0.05, type II error β was 0.10, the 2-tailed P value was < 0.05, the study and control group ratio was 1:4, and at least 137 patients in the F-URS group, 548 patients in the SWL group should be included, respectively. It was calculated by PASS 11.0 (Power Analysis and Sample Size 11.0, NCSS Inc., USA) [14].
Propensity score-matching
We used the propensity score matching (PSM) method to adjust baseline confounding variables between the URS and SWL group to derive more accurate conclusions. Multivariate logistic regression analysis was used to determine propensity scores for each patient based on age, gender, BMI, comorbidities, previous history of urinary stone treatment, and stone data (all baseline variables in Table 1). The F-URS and SWL groups were matched 1:4 using a caliper width of 0.2 of the standard deviation of the logit of the propensity score through the nearest neighbor matching (Fig. 2).
Table 1.
Demographics and clinical data in this cohort according to the surgery type before and after PSM
| Variables | Propensity before 699 patients | Propensity after 555 patients | ||||
|---|---|---|---|---|---|---|
| SWL | F-URS | P value | SWL | F-URS | P value | |
| Number of patients (%) | 568 (100.0) | 131 (100.0) | 431 (100.0) | 124 (100.0) | ||
| Demographic characteristics | ||||||
| Median age (years) | 47.8 ± 15.2 | 53.9 ± 12.2 | < 0.001 | 51.9 ± 13.8 | 53.3 ± 12.1 | 0.267 |
| Gender (male) | 401 (70.6) | 77 (58.8) | 0.009 | 278 (64.5) | 77 (62.1) | 0.623 |
| BMI (kg/m2) | 25.3 ± 5.1 | 25.8 ± 4.6 | 0.277 | 25.6 ± 5.0 | 25.8 ± 4.7 | 0.666 |
| Comorbidities | ||||||
| Hypertension (yes) | 53 (9.3) | 22 (16.8) | 0.013 | 50 (11.6) | 18 (14.5) | 0.383 |
| Diabetes Mellitus (yes) | 75 (13.2) | 28 (21.4) | 0.017 | 65 (15.1) | 23 (18.5) | 0.352 |
| Coronary heart disease (yes) | 33 (5.8) | 7 (5.3) | 0.836 | 23 (5.3) | 6 (4.8) | 0.826 |
| Previous history of urinary stone | 0.018 | 0.299 | ||||
| No or spontaneous passage | 510 (89.8) | 108 (82.4) | 377 (87.5) | 104 (83.9) | ||
| SWL, URS or PCNL | 58 (10.2) | 23 (17.6) | 54 (12.5) | 20 (16.1) | ||
| Stone characteristics | ||||||
| Stone location | 0.276 | 0.721 | ||||
| Pelvis or pelvic-ureteral junction | 416 (73.2) | 102 (77.9) | 327 (75.9) | 96 (77.4) | ||
| Upper or middle calyx | 152 (26.8) | 29 (22.1) | 104 (24.1) | 28 (22.6) | ||
| Stone side (left) | 305 (53.7) | 70 (53.4) | 0.957 | 237 (55.0) | 64 (51.6) | 0.506 |
| Stone size (diameter, mm) | 12.3 ± 1.6 | 12.1 ± 1.5 | 0.416 | 12.2 ± 1.5 | 12.2 ± 1.5 | 0.965 |
| Hounsfield unit of stone (Hu) | 731 ± 230 | 732 ± 230 | 0.985 | 734 ± 226 | 728 ± 232 | 0.799 |
| Hydronephrosis (diameter, mm) | 0.358 | 0.734 | ||||
| G0, G1 and G2 | 434 (76.4) | 105 (80.2) | 338 (78.4) | 99 (79.8) | ||
| G3 and G4 | 134 (23.5) | 26 (19.8) | 93 (21.6) | 25 (20.2) | ||
Continuous variables were expressed as median (interquartile range); categorical variables were reported as number (percentage). Before PSM, independent samples Student’s t-test was used to compare mean of two continuous normally distributed variables and the Mann–Whitney U test was run to determine mean of two continuous non-normally distributed variables. After PSM, the categorical variables were compared by binary conditional logistic regression. Paired samples Student’s t-test was used to compare the mean of two continuous normally distributed variables, and the Wilcoxon test was used to compare the mean of two continuous non-normally distributed variables in univariate analysis
PSM propensity score-matching, BMI body mass index, SWL extracorporeal shock wave lithotripsy, F-URS flexible ureterorenoscopy, PCNL percutaneous nephrolithotomy, Hu Hounsfield unit, G grade
Fig. 2.
Plot of the propensity score-matched study. A: dot plot of standardized mean difference. B: histogram of standardized mean differences (before and after). C: line plot of individual differences
Statistical analysis
Data were analyzed by SPSS 22.0 for Windows (SPSS Inc., Chicago, IL, USA). Continuous variables were presented as the median (interquartile range). Categorical variables were reported as the number (percentage). Before PSM, independent samples Student’s t-test was used to compare the mean of two continuous normally distributed variables. The Mann–Whitney U test was used to compare the mean of two continuous non-normally distributed variables. The c2 test or Fisher’s exact test was used for categorical variables. After PSM, the categorical variables were compared by binary conditional logistic regression. Paired samples Student’s t-test was used to compare the mean of two continuous normally distributed variables, and the Wilcoxon test was used to compare the mean of two continuous non-normally distributed variables in univariate analysis. A p-value of less than 0.05 was considered statistically significant.
Results
The final study included 699 patients who were separated into two groups. There were 568 individuals who received SWL and 131 who received F-URS. The mean age of patients in the SWL group was younger (47.75 years vs. 53.89 years, P < 0.001), and the ratio of the male was higher (70.60% vs. 58.80%, P = 0.009) compared with the patients in F-URS group. In addition, the patients in SWL groups also had a higher ratio of concomitant comorbidities (P = 0.013 and P = 0.017) and previous history of urinary stone treatment (P = 0.018) compared with the patients in the F-URS group. After PSM, we balanced baseline variables between the two groups. Finally, there were 431 patients left in the SWL group and 124 patients left in the F-URS group, respectively (Table 1).
After PSM, we found that the SFR, complete SFR, retreatment rate and adjunctive procedure rate was comparable between SWL group and F-URS group (P = 0.323, P = 0.284, P = 0.169, and P = 0.358). The patients in the SWL group experienced a shorter operative time than the patients in the F-URS group. The complications were equivalent between the two groups in minor complications, major complications, mortality, SIRS, sepsis, steinstrasse renal colic (analgesic requirement), and renal hematoma (asymptomatic) (all P > 0.05). The incidence of ureteral injury (perforation) was higher in the F-URS group than in the SWL group (1.6% vs. 0%, P = 0.008). The hospital stay was significantly shorter (one day vs. two days, P < 0.001), and the cost was also considerably less (165 vs. 4,142, P < 0.001) in the SWL group compared with the F-URS group, see details in Table 2.
Table 2.
Treatment outcome and postoperative data in this cohort according to the surgery type before and after PSM
| Variables | Propensity before 699 patients | Propensity after 555 patients | ||||
|---|---|---|---|---|---|---|
| SWL | F-URS | P value | SWL | F-URS | P value | |
| Number of patients (%) | 568 (100.0) | 131 (100.0) | 431 (100.0) | 124 (100.0) | ||
| Treatment outcome | ||||||
| Operative time (minutes) | 33 ± 3 | 75 ± 8 | < 0.001 | 35 ± 3 | 75 ± 8 | < 0.001 |
| SFR after procedure at 1 month | 494 (87.0) | 120 (91.6) | 0.144 | 379 (87.9) | 113 (91.1) | 0.323 |
| Complete SFR after procedure at 1 month | 484 (85.2) | 116 (88.5) | 0.323 | 362 (84.0) | 109 (87.9) | 0.284 |
| Retreatment rate | 49 (8.6) | 7 (5.3) | 0.212 | 37 (8.6) | 6 (4.8) | 0.169 |
| Adjunctive procedure rate | 14 (2.5) | 5 (3.8) | 0.391 | 11 (2.6) | 5 (4.9) | 0.385 |
| Complications | ||||||
| Minor complications (Clavien 1–2) | 28 (4.9) | 8 (6.1) | 0.583 | 19 (4.4) | 7 (5.6) | 0.566 |
| Major complications (Clavien 3–4) | 14 (2.5) | 2 (1.5) | 0.518 | 7 (1.6) | 2 (1.8) | 0.993 |
| Mortality (Clavien 5) | 0 (0.0) | 0 (0.0) | 1.000 | 0 (0.0) | 0 (0.0) | 1.000 |
| SIRS | 22 (3.9) | 8 (6.1) | 0.256 | 16 (3.7) | 7 (5.6) | 0.341 |
| Sepsis | 1 (0.2) | 1 (0.8) | 0.257 | 1 (0.2) | 1 (0.8) | 0.347 |
| Steinstrasse | 11 (1.9) | 0 (0.00) | 0.108 | 3 (0.7) | 0 (0.0) | 0.352 |
| Renal colic (analgesic requirement) | 7 (1.2) | 0 (0.00) | 0.202 | 4 (0.9) | 0 (0.0) | 0.282 |
| Renal hematoma (asymptomatic) | 2 (0.4) | 0 (0.00) | 0.496 | 2 (0.5) | 0 (0.0) | 0.447 |
| Ureteric injury (perforation) | 0 (0.0) | 2 (1.5) | 0.003 | 0 (0.0) | 2 (1.6) | 0.008 |
| Cost-effective data | ||||||
| Hospital stay (days) | 1.0 (1.0, 1.0) | 2.0 (1.0, 2.0) | < 0.001 | 1.0 (1.0, 1.0) | 2.0 (1.0, 2.0) | < 0.001 |
| Mean costs (USD/$) | 165 (165, 165) | 4128 (3864, 4531) | < 0.001 | 165 (165, 165) | 4142 (3868, 4537) | < 0.001 |
Continuous variables were expressed as median (interquartile range); categorical variables were reported as number (percentage). Before PSM, independent samples Student’s t-test was used to compare mean of two continuous normally distributed variables and the Mann–Whitney U test was run to determine mean of two continuous non-normally distributed variables. After PSM, the categorical variables were compared by binary conditional logistic regression. Paired samples Student’s t-test was used to compare the mean of two continuous normally distributed variables, and the Wilcoxon test was used to compare the mean of two continuous non-normally distributed variables in univariate analysis
PSM propensity score-matching, SWL extracorporeal shock wave lithotripsy, F-URS flexible ureterorenoscopy, SFR Stone-free rate, SIRS systemic inflammatory response syndrome, USD/$: dollar, N/A not applicable
Discussion
The optimal management modality of solitary non-lower pole kidney stones ≤ 20 mm is controversial for urologists. Both SWL and F-URS are recommended as the first choice among available treatment modalities. This study aimed to compare the efficacy, safety, and cost between SWL and F-URS. Furthermore, this prospective PSM cohort provides a fair comparison; SWL had equivalent efficacy while more benefit in safety and cost than F-URS in treating patients with solitary non-lower pole kidney stones ≤ 20 mm.
The SFR of SWL was reported as between 60 and 90% in the literature; the rate is around 80% for renal pelvis stones [15, 16]. The available data regarding F-URS show success rates of around 90% [17, 18]. We achieved an SFR of 87% versus 91.6% in patients treated with SWL and F-URS, respectively, and it was parallel to results in the literature. We found that the SFR, retreatment rate, and adjunctive procedure rate were all equivalent between the SWL and F-URS groups for treating patients with non-lower pole kidney stones < 20 mm. In line with this, in a retrospective cohort including 99 patients with renal pelvis stones of 10–20 mm, both the SFR (91.4% vs 86.0%, P > 0.05) and complications (7.6% vs 6.3%, P > 0.05) were equivalent between F-URS and SWL group, which was performed by electrohydraulic lithotripter under fluoroscopic guidance [3]. In another retrospective study including 174 patients with radioopaque solitary upper or mid renal calyx stones of 10–20 mm, Cecen et al. [11] also indicated that F-URS and SWL have similar treatment outcomes in SFR (92% vs. 87%, P = 0.270), retreatment rate (7.5% vs. 12.9%, P = 0.270), and complications (7.5% vs. 6.4%, P = 0.780). Therefore, they concluded that F-URS should be kept as the second treatment alternative or reserved for cases where SWL proves non-viable.
Additionally, another two prematurely closed RCTs included non-lower pole kidney stones [19, 20], which failed to recruit a sufficient number of patients (enrolling only 44 and 18 patients, respectively). These studies found no statistical difference between F-URS and SWL in terms of SFR three months after the procedure and complication rates within one month in patients with kidney stones of 5–20 mm. However, the results of these early terminated studies did not conclude the superiority of a technique. In addition, the technical development of the third-generation lithotripters that use electromagnetic energy also led to an increase of SFR up to 88.5% and subsequently, a reduction of retreatment rates. Moreover, it could also reduce treatment time per session and avoid complications [21].
On the contrary, in a multi-center retrospective study including 297 patients with radiolucent renal stones of 10–20 mm (71.3% of them had non-lower pole stones), F-URS provided significantly higher SFR (87% vs. 66.5%, P < 0.001), lower need for auxiliary treatment (8.7% vs. 21.9%, P < 0.001), and lower overall complication rates (7.6% vs. 10.9%, P < 0.001) compared with SWL [22]. Another multi-center retrospective study, including 736 patients with renal stones of 10–20 mm (75% of them had non-lower pole stones), demonstrated that the SWL group had a lower SFR (77.2% vs 86.1%) and more need for auxiliary treatments (22.8% vs 10%) compared with F-URS [23]. This discrepancy may be attributed to the difference in inclusion criteria; they included the cases with different locations like the lower pole or multiple caliceal stones that diminished the SFR of SWL.
The assessment of complications is crucial for further comparison of both interventions. There was a similarly low perioperative morbidity between the two groups in this study. Most complications were minor and did not require management. Therefore, both interventions are safe procedures for treating non-lower pole kidney stones. However, it is worth noting that ureteral perforation occurred in two patients of the F-URS group as a Clavien grade 3B complication due to its invasive nature. They were treated conservatively with the placement of a stent, but this was not reported in patients after SWL.
This study also demonstrated that SWL has significant superiority in terms of minimal cost and reduced hospital stay compared with F-URS. All patients in the SWL group were treated as day surgery, and they could achieve normal activity as soon as possible. In a retrospective study including 2724 ureteric stones conducted in 2017, patients treated by SWL had a shorter length of stay with fewer overall attendances and procedures at three months than those treated with URS. Farag et al. also concluded that during a pandemic such as COVID-19, SWL might have benefits in preserving hospital resources and limiting opportunities for virus transmission compared to URS [24]. The addition of special instruments developed for F-URS like laser fibers and tipless nitinol baskets also increases the cost of this procedure. Besides, the requirement of expensive repair, especially in the learning curve of the F-URS, should also be kept in mind in the management of these patients. SWL has the benefit of avoiding general anesthesia and its associated complications and cost. Therefore, the medical costs were also dramatically reduced.
There are several limitations. First, it is a non-randomized study design; residual confounding by unknown variables may still occur. However, the known confounders were controlled by PSM. Second, the stone-free status was evaluated using KUB and ultrasound instead of CT, which might result in an overestimated SFR. Third, we cannot report long-term complications, such as the incidence of ureteral stenosis. Fourth, our study did not evaluate postoperative pain scores. However, a previous study has observed a significant difference in postoperative pain in favor of SWL [25]. This could be explained by the routinely ureteral stent use after F-URS but not after SWL. Fifth, the percutaneous nephrolithotomy technique was not considered in this study. Although PNL is effective, it has disadvantages in terms of invasiveness, blood loss, radiation exposure, hospital stay, and complications compared with SWL or F-URS technique [22], and it is more preferred in the treatment of kidney stones > 20 mm or lower pole kidney stones with unfavorable anatomy. Sixth, these conclusions only applied to patients with BMI < 30 kg/m2 and ureter stone density ≤ 1000 HU. Seventh, no data were available on the stone compositions. However, the Hu value of CT is, at best, an estimate of the stone composition. Eighth, considering this study was conducted during the COVID-19 pandemic, the generalization of the results needs further validation. Nevertheless, in the absence of prospective research on the treatment of non-lower pole kidney stones, this study is the first larger prospective study comparing the efficacy, safety, and cost between SWL and F-URS. Further multi-center RCTs are needed.
Conclusion
This prospective PSM cohort demonstrated that SWL had equivalent efficacy with more safety and cost benefits than F-URS in treating patients with solitary non–lower pole kidney stones ≤ 20 mm. During the COVID-19 pandemic, SWL may have benefits in preserving hospital resources and limiting opportunity for virus transmission, compared to URS. These findings may guide clinical practice.
Acknowledgements
We give special thanks to all the colleagues at the Department of Urology of Shengjing Hospital for their help and support. We thank International Science Editing (http://www.internationalscienceediting.com) for editing this manuscript. The authors would like to thank all of the study participants.
Author contributions
JL, and LS had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. JL, and LS: protocol/project development. SB, GL, YZ, CP, JL, and LS: data collection or management. YZ, and SB: data analysis. SB, GL, YZ, JL, and LS: manuscript writing/editing.
Funding
This study was financially supported by The 345 Talent Project of Shengjing Hospital, Natural Science Foundation of Liaoning Science and Technology Department (Grant Number 2020-BS-093), and Natural Science Foundation of Liaoning Education Department (Grant Number QN2019013). These sponsors had no role in the study design; in the collection, analysis or interpretation of data; in the writing of the report; or in the decision to submit the article for publication.
Availability of data and materials
The data are not available and the data used are confidential.
Declarations
Conflict of interests
Jia Li, and Liping Shan certifies that all conflicts of interest, including specific financial interests and relationships and affiliations relevant to the subject matter or materials discussed in the manuscript (e.g., employment/affiliation, grants or funding, consultancies, honoraria, stock ownership or options, expert testimony, royalties, or patents filed, received, or pending), are the following: None.
Ethical approval
Ethical approval (No. 2020PS520K) was provided by the Ethics Committee of Shengjing Hospital Affiliated China Medical University on 9 June 2020. Informed consent from all eligible subjects was obtained. The clinical research registry UIN is ChiCTR2000033790 (http://www.chictr.org.cn/index.aspx). The study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki.
Consent for publication
Informed consent from all eligible patients was obtained.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Contributor Information
Song Bai, Email: baisongcmu81@163.com.
Yunhong Zhan, Email: zhanyunhong81@163.com.
Chunyu Pan, Email: panchunyu81@163.com.
Gang Liu, Email: liugangcmu@163.com.
Jia Li, Email: lijiacmu@163.com.
Liping Shan, Email: shanliping81@163.com.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data are not available and the data used are confidential.