Effect of the External Physical Vibration Lithecbole on the Discharge of Upper Urinary Stones: A Systematic Review and Meta-analysis Zi-hao Xu1, Jian-lin Lv1, Shuang Zhou1, chun-ping Jia1, Hao Wang1* Purpose: The external physical vibration lithecbole (EPVL) is a new device that accelerates the discharge of uri- nary stones by changing the patient's body position and providing multi-directional simple harmonic waves. It is clinically employed to improve the stone-free rate (SFR). However, it is not widely accepted in clinical practice due to the lack of high-level evidentiary support and a standard protocol. The present meta-analysis aims at the evaluation of the efficacy and safety of EPVL treatment in improving the SFR. Methods: This study was a systematic review and meta-analysis. A systematic literature review was conducted using PubMed, Scopus, Embase, Medline, the Web of Science, and the Cochrane Library to find randomized con- trolled trials (RCTs) as recent as April 2020 that evaluated the efficacy and safety of EPVL treatment for patients with stones/residual stones in the upper urinary tract. Results: In total, 7 prospective studies with 1414 patients were included. Compared with patients in the control group, patients treated with an EPVL (the intervention group) had higher SFRs (95% CI: 0.59-0.86, RR = 0.71, P = .0004) and lower complication rates (95% CI: 1.37-3.12, RR = 2.07, P = .0006). In a subgroup analysis based on previous surgery (ESWL, RIRS), the intervention group had an improved SFR as compared to the control group (95% CI: 0.59-0.95, RR = 0.75, P = .02; 95% CI: 0.56-0.73, RR = 0.64, P < .00001, respectively). In a subgroup analysis based on stone location, the SFRs for stones in the upper/middle/lower calyx and renal pelvis were signif- icantly higher in the intervention group than in the control group: for residual stones in the upper and middle calyx, 95% CI: 0.63-0.98, RR = 0.79, and P = .03; for residual stones in the lower calyx, 95% CI: 0.54-0.75, RR = 0.64, and P < .00001; for residual stones in the renal pelvis, 95% CI: 0.47-0.79, RR = 0.61, and P = .0002. However, the SFRs for ureter stones were not significantly different between groups (95% CI: 0.82 -1.05, RR = 0.93, P = .23). Conclusion: The external physical vibration lithecbole can effectively improve the SFR after ESWL and RIRS without significant side effects, especially for residual stones in the upper/middle/lower calyx and renal pelvis. Keywords: external physical vibration lithecbole; upper urinary stones; residual stones, meta-analysis INTRODUCTION Urinary tract stones are a common urological dis-ease, and create life and economic burdens for about 5-15% of the world's population.(1,2) With the development of technology, several surgical proce- dures can be used to treat stones, including extracor- poreal shock wave lithotripsy (ESWL), retrograde in- trarenal surgery (RIRS), percutaneous nephrolithotomy (PCNL), and laparoscopic surgery. Because surgical equipment and treatment concepts are continuously updated, the phenomenon of residual stones has been greatly improved. However, the presence of residual stones after surgery remains a bothersome problem for urologists. Residual stones can potentially reaggregate and grow, thereby causing recurrent stone formation, infection, renal colic, obstruction, and eventually kid- ney failure.(3) Many methods can promote the discharge of residual stones, including drinking more water, exercising more, medical expulsive therapy (MET), and percussion, diu- Department of Urology, The Affiliated Jiangning Hospital with Nanjing Medical University, Nanjing, Jiangsu 211100, China. *Correspondence: Department of Urology, The Affiliated Jiangning Hospital of Nanjing Medical University, No. 168 Gushan Road, Dongshan Street, Nanjing 211100, China. Tel: +86-25-52178496; Fax: +86-25-52178496. E-mail: luanshiwhxx01@163.com. Received August 2020 & Accepted January 2021 resis, and inversion (PDI).(4-7) Some emerging technolo- gies, such as the use of iron oxide microparticles and ul- trasonic propulsion, can also improve the stone removal rate;(8,9) however, these two technologies have not been widely used in clinical practice. Recently, based on the principles of PDI treatment, the external physical vi- bration lithecbole (EPVL) device has been designed to discharge stone fragments. The device mainly provides harmonic vibration via stationary and mobile vibrators, thereby pushing the stones to discharge from the body. Several randomized controlled trials (RCTs) have com- pared the efficacy and safety of the EPVL in treating upper urinary tract residual stones. In 2015, a study conducted by Long et al. showed that, in the treatment of lower-pole renal stones, the stone removal rate of the EPVL plus ESWL group reached 76.5%, while that of the group that received ESWL treatment alone was only 43.8% (P = 0.008).(10) EPVL treatment can also accelerate the discharge of residual stones after RIRS. Zhang et al.(11) designed a prospective randomized con- trolled study to determine the length of time between Urology Journal/Vol 18 No. 1/ January-February 2021/ pp. 19-27. [DOI: 10.22037/uj.v0i0.6417] REVIEW RIRS and EPVL treatment that can achieve the best therapeutic effect for patients with residual stones; the results showed that the earlier the treatment, the higher the stone removal rate, and the greater the reduction of corresponding complications. However, to date, no systematic review or meta-analy- sis has evaluated the effectiveness of EPVL. Therefore, a systematic review and meta-analysis were conduct- ed to assess the efficacy and safety of the EPVL in the treatment of upper urinary tract stones or stone frag- ments. MATERIALS AND METHODS Literature search The systematic review was performed according to the Cochrane review guidelines and the PRISMA (Pre- ferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. A systematic literature review using PubMed, Scopus, Embase, Medline, the Cochrane Library, and the Web of Science was per- formed to identify RCTs that had assessed the efficacy and safety of the EPVL in the treatment of upper uri- nary tract stones or stone fragments. The search strategy was [("inversion" OR "vibration" OR "EPVL") AND ("stone" OR "calculus" OR "urolithiasis")]. The refer- ence lists of relevant publications were also checked to identify any additional potential studies, and the poten- tially eligible studies from the cited references in the enrolled papers were also assessed. In addition, abstract booklets and presentations from annual academic con- Table 1. Baseline characteristics of individual studies included in the meta-analysis. Study Country Study design Mean age (T/C, years) BMI (T/C) Sample size (T/C) LE Quality Long et al. 2016 (10) China RCT 44 ± 9.5/45 ± 9.9 25.2 ± 3.4/25.6 ± 2.9 34/37 1b 3 Wu et al.2017 (15) China RCT 47.1 ± 1.0/46.9 ± 1.2 24.5 ± 0.3/24.1 ± 0.3 87/86 1b 5 Liu et al. 2017 (12) China RCT 37.4 ± 15.3/38.3 ± 16.8 NA/NA 236/222 1b 3 Wu et al. 2018 (14) China RCT 42.9 ± 1.5/42.7 ± 1.3 23.6 ± 0.3/23.8 ± 0.3 76/77 1b 5 Tao et al.2018 (13) China RCT 49.3 ± 6.1/50.4 ± 5.7 23.6 ± 2.9/23.1 ± 3.3 127/144 1b 5 Jing et al.2018 (16) China RCT 38.7 ± 10.72/38.2 ± 10.6 24.1 ± 2.98/23.9 ± 2.6 56/56 1b 4 Zhang et al.2019 (11) China RCT 47.58 ± 10.26a 23.95 ± 2.91a 45a 1b 5 49.72 ± 11.2b 24.78 ± 3.17b 44b 51.83 ± 9.31c 24.06 ± 3.56c 42c /47.04 ± 9.1d /24.55 ± 3.59d /45d Abbreviations: T/C: treatment group vs. control group. a, b, c, d: The study by Zhang et. al (2019) reports three treatment groups, a, b and c, and group d is the control group. Figure 1. Flow chart of the study selection. The effect of EPVL on upper urinary stones-Xu et al. Review 20 Vol 18 No 1 January-February 2021 21 ferences were also consulted, and the corresponding au- thors of unpublished studies were contacted via email. The literature retrieval was halted in April 2020. Two of the authors (Zi-hao Xu and Hao Wang) independently and thoroughly carried out the literature search, article selection, quality assessment, and data extraction, and disagreements were resolved by an open discussion with a third reviewer. Inclusion and exclusion criteria The inclusion criteria for eligible studies were as fol- lows: (1) the report of RCTs; (2) the comparison of EPVL treatment with conservative non-intervention; (3) the report of sufficient data, including the stone size and stone location; (4) published in English. The ex- clusion criteria were as follows: (1) reviews, editorials, or conference abstracts; (2) repeated publications; (3) retrospective studies; (4) published in languages other than English. Assessment of the quality of studies and data extraction The GRADE system was used to assess the level of evidence (LE), and the Jadad scale was used to assess the methodological quality of all included studies. Fur- thermore, the Cochrane risk-of-bias tool was utilized to evaluate the potential kinds of bias. The extracted data included the study design, methodological quali- ty, stone size, previous surgery, stone location, treat- ment method, follow-up time, stone-free rate (SFR), and stone-related complications. In the control group, patients were recommended to increase their physical activity and fluid intake. In the intervention group, Table 2a. Detailed comparisons and results of eligible studies. Study Previous Stone Stone Intervention Follow-up time No. of No. of surgery location size strategy (T/C) stone-free complications patients (T/C) (T/C) Long et al. ESWL Lower 6-20 mm EPVL/ 3 weeks 26 (76.5%) 5 (14.7%) 2016 calyx before Observation /18 (48.6%) /6 (16.2%) ESWL Wu et al. RIRS Upper ≤4 mm EPVL/ 4 weeks 78 (89.7%) 6 (6.9%) 2017 urinary after RIRS Observation /52 (60.5%) /28 (32.2%) Liu et al. NA Distal ureter 3.2-10 mm EPVL + 2 weeks 223 (94.5%) NA/NA 2017 tamsulosin/tamsulosin /208 (93.7%) Wu et al. ESWL Upper ≤15 mm EPVL/ 4 weeks 69 (90.8%) 2 (2.6%) 2018 urinary before Observation /58 (75.3%) /5 (6.5%) ESWL Tao et al. ESWL Upper 10-20 mm EPVL/ 4 weeks 117 (92.1%) 11 (8.7%) 2018 urinary before Observation /121 (84%) /10 (6.9%) ESWL Jing et al. ESWL Upper Largest EPVL/ 4 weeks 31 (55.4%) 24 (42.9%) 2018 urinary stone Observation /13 (23.2%) /38 (67.9%) diameter 8-15 mm before ESWL Zhang et al. RIRS Unilateral ≤4 mm EPVLa, b, c 4 weeks 41a (91.1%) 4a (8.9%) 2019 renal after RIRS /Observationd 37b (84.1%) 8b (18.2%) 32c (76.2%) 10 c (23.8%) /23d (51.1%) /21d (46.7%) Figure 2. Comparison between total SFRs for patients in the treatment (EPVL) and control groups. The effect of EPVL on upper urinary stones-Xu et al. Vol 18 No 1 January-February 2021 39 patients were treated with an EPVL device beside the above recommendations. The recording of complica- tions included the reported effects of the treatment, such as hematuria, leukocyturia, and lumbago. Statistical analysis The methodological assessment was accomplished us- ing RevMan 5.3 software. Because the SFR and com- plications in all included studies were dichotomous variables, the pooled risk ratios (RRs) with 95% con- fidence intervals (CIs) were implemented for statistical analysis. Subgroup analyses were conducted according to the stone location and complication type. The sta- tistical heterogeneity among the included studies was assessed by chi-square tests based on Q and I2 statis- tics (minimal heterogeneity: 0-25%, moderate heter- ogeneity: 25-50%, significant heterogeneity: >50%.) Fixed-effect models were used to analyze the hetero- geneous data (I2 < 50%), and random-effects models were used to analyze the heterogeneous data (I2 > 50%). A two-sided P-value < 0.05 was considered to be sta- tistically significant. Furthermore, the potential hetero- geneity and publication bias were tested by performing subgroup pooled analysis and sensitivity analysis, and by creating funnel plots. RESULTS In total, 235 references were obtained from the initial examination. After screening layer-by-layer, 7 RCT studies(10-16) comprising 1414 patients were ultimately included. The basic features of the included studies are reported in Tables 1 and 2. As reported in these studies, 747 pa- tients received EPVL treatment for upper urinary tract stones or stone fragments, while 667 patients were al- located to the control group. All included studies had a low risk of bias, but the performance bias was high. The risk of bias for each included study is summarized in Table 3. Regardless, the evaluation of the results was blinded and relatively objective. SFR All the included studies(10-16) reported SFRs after inter- vention, and the SFR was concluded based on imaging (ultrasound, KUB, non-contrast CT scan when neces- sary) reflecting the discharge of residuals stones. The EPVL (intervention) group presented obviously higher SFRs than the control group (95% CI: 0.59-0.86, RR = 0.71, P = .0004) with random effects, but there was a significant heterogeneity among these studies (I2 = 92%), as presented in Figure 2. Therefore, a subgroup analysis based on previous surgery (ESWL, RIRS) in the intervention group was performed, and an improved SFR was found as compared to the control group (95% CI: 0.59-0.95, RR = 0.75, P = .02 and 95% CI: 0.56- 0.73, RR = 0.64, P < .00001, respectively) (Figure 3). In a subgroup analysis based on stone location, the SFRs for stones in the upper/middle/lower calyx and the renal pelvis were significantly higher in the intervention group than in the control group: for residual stones in the upper and middle calyx, 95% CI: 0.63-0.98, RR = 0.79, and P = .03; for residual stones in the lower calyx, 95% CI: 0.54-0.75, RR = 0.64, and P < .00001; for residual stones in the renal pelvis, 95% CI: 0.47-0.79, RR = 0.61, and P = .0002. However, the SFRs for ureter stones were not significantly different between groups (95% CI: 0.82 -1.05, RR = 0.93, P = .23) (Figure 4). Complications The overall complication rates between the interven- tion group and the control group are presented in Fig- ure 4. Data on complications in the EPVL and control groups were provided for a total of 220 events in six studies.(10,11,13-16) In the meta-analysis, the complication Table 2b. Types of complications. Study Treatment group Observation group Hematuria Lumbago Leukocyturia Dizziness Hematuria Lumbago Leukocyturia Dizziness Long et al. 2016 2 2 NA 1 4 2 NA NA Wu et al. 2017 3 NA 3 NA 18 NA 10 NA Liu et al. 2017 NA NA NA NA NA NA NA NA Wu et al. 2018 1 NA 1 NA 3 NA 2 NA Tao et al. 2018 NA NA NA 7 NA NA 3 NA Jing et al. 2018 14 9 1 NA 19 14 3 NA Zhang et al. 2019 2a/5b/5c NA 2a/3b/5c NA 11 NA 10 NA Abbreviations: T/C: treatment group vs. control group; NA: not available. a, b, c, d: The study by Zhang et al. (2019) reports three treatment groups, a (3 days after RIRS), b (7 days after RIRS), and c (14 days after RIRS), and group d is the observation group. Study Random- Allocation Blinding of Blinding of Incomplete Selective outcome Other sequence generation concealment participants outcome outcome data reporting bias (selection bias) (selection bias) (performance bias) assessment (attrition bias) (reporting bias) (detection bias) Long et al. 2016 LOW UNCLEAR HIGH LOW LOW UNCLEAR LOW Wu et al. 2017 LOW LOW HIGH LOW LOW LOW LOW Liu et al. 2017 UNCLEAR UNCLEAR HIGH LOW LOW UNCLEAR UNCLEAR Wu et al. 2018 LOW LOW HIGH LOW LOW LOW LOW Tao et al. 2018 LOW LOW HIGH LOW LOW LOW LOW Jing et al. 2018 LOW UNCLEAR HIGH LOW LOW UNCLEAR LOW Zhang et al. 2019 LOW UNCLEAR HIGH LOW LOW LOW LOW Table 3. Risk of bias of included studies. The effect of EPVL on upper urinary stones-Xu et al. Vol 18 No 1 January-February 2021 23 rate was found to be significantly lower in the inter- vention group than in the control group (95% CI: 1.37- 3.12, RR = 2.07, P = .0006) (Figure 5) with random effects, and also exhibited significant heterogeneity (I2 = 57%). Subgroup meta-analysis was then carried out Figure 3. Comparison of SFRs for different previous surgeries in patients in the EPVL and control groups. as subsequently described, and the results are exhibited in Figure 6. 1. Hematuria Five studies including 775 participants (384 in the in- tervention group and 391 in the control group) report- Figure 4. Comparison between SFRs for different stone locations in patients in the EPVL and control groups. The effect of EPVL on upper urinary stones-Xu et al. Vol 18 No 1 January-February 2021 41 ed the incidence of hematuria after treatment. The rate was significantly lower in the intervention group than in the control group (95% CI: 1.62-3.45, RR = 2.37, P < .00001), and low heterogeneity was detected among these studies (I2 = 20%). 2. Lumbago Only two studies reported the incidence of lumbago after treatment. There was no significant difference between the intervention and control groups (95% CI: 0.72-2.88, RR = 1.44, P = .31). 3. Leukocyturia Four studies including 704 participants (350 in the in- tervention group and 354 in the control group) reported the incidence of leukocyturia after treatment. The rate was significantly lower in the intervention group than in the control group (95% CI: 1.68-5.12, RR = 2.93, P = .0001), and no heterogeneity was detected among these studies (I2 = 0.0%). 4. Dizziness Only two studies reported the incidence of dizziness after treatment. There was no significant difference between the intervention and control groups (95% CI: 0.11-1.25, RR = 0.37, P = .11). Figure 5. Comparison between complication rates of patients in the EPVL and control groups. Figure 6. Comparison of complication rates for different types of complications in patients in the EPVL and control groups. The effect of EPVL on upper urinary stones-Xu et al. Review 24 Vol 18 No 1 January-February 2021 25 Sensitivity analysis and publication bias To examine the stability of the outcome, a sensitivity analysis was conducted. After the research by Liu et al.(12) was excluded, the I2 value changed from 92% to 82%, indicating that this research was the main cause of the heterogeneity. The forest plot without the inclu- sion of Liu et al.’s article is presented in Figure 7. All included studies reported SFRs, and a funnel plot for the SFR was created. The results demonstrate that there existed some publication bias, as the funnel plot was not symmetric (Figure 8). DISCUSSION The problem of residual stones has plagued urologists for decades. Although surgery can be performed to re- move most stones, and while complete stone removal can be achieved in some patients, residual stones re- main an unavoidable problem. Additionally, 43-77% of asymptomatic residual stones will progress accord- ingly, causing corresponding symptoms.(17,18) In 2000, Honey et al.(4) reported for the first time that PDI ther- apy can effectively promote the excretion of calculus in the kidney. A meta-analysis showed that PDI ther- apy can improve the discharge of calculus after ESWL (OR: 0.62; 95% CI: 0.47-0.82). Although it has been concluded that PDI therapy is effective, only two re- lated studies were included, and evidence of its effec- tiveness is lacking. Moreover, because the percussion in PDI therapy is not widely promoted in clinical practice, there have been few relevant studies. However, the EPVL device has gradually been used clinically since its invention in China, and many re- searchers have conducted related clinical studies. This equipment includes a rotating bed and a physical vibra- tion device, which accelerates the discharge of stones by changing the patient's body position and providing multi-directional simple harmonic waves. The EPVL Figure 7. Sensitivity analysis forest plots. Figure 8. Funnel plot of publication bias. The effect of EPVL on upper urinary stones-Xu et al. Vol 18 No 1 January-February 2021 43 is primarily used as an adjuvant treatment of residual stones after ESWL and RIRS. In 2019, a meta-anal- ysis conducted by Chung et al. revealed that residual stones are more common after ESWL and RIRS than after PCNL, with likelihoods reaching 23.1-91.5% and 45.6-96.7%, respectively.(19) However, in the present subgroup analysis, EPVL treatment was found to better prevent residual stones after these two treatments. The location of residual stones is a significant factor that affects their removal rate.(20) Due to the effect of gravity, stones remaining in the lower half of the kidney account for a large proportion, and are more difficult to remove than residual stones in the upper and middle areas.(21,22) However, the present subgroup analysis re- vealed that EPVL treatment can solve this problem very well; it can significantly improve the SFR in the lower kidney, and also in other parts of the kidney. The ureter is also a common site of urinary tract stones, but the subgroup analysis demonstrated that EPVL treatment has no significant effect on the SFR of ureteral stones. A prospective study conducted by Liu et al.(12) showed that EPVL treatment can achieve the same stone remov- al rate as medical expulsive therapy (MET) for lower ureteral stones of less than 10 mm in size, and there was no significant difference between the rate of stone discharge in the EPVL group and the MET group; re- searchers performed surgery on patients whose stones had not passed after two weeks, and found that their ureters had strictures. The safety of EPVL treatment is also an important issue that must be considered in clinical practice. There have been no reports of serious complications in many known studies; while there have been reports that patients experienced dizziness, nau- sea, and skin redness after receiving EPVL treatment, these side-effects all relieved themselves. The EPVL is a physical therapy device, and is a safe and non-in- vasive treatment method. The subgroup analysis of the probability of complications revealed that patients who received EPVL treatment had a lower probability of complications, including hematuria, lumbago, leuko- cyturia, and dizziness. EPVL treatment was found to reduce the phenomena of hematuria and leukocyturia, which are usually caused by the movement of stones in the ureter to the mucosa. It is believed that the fol- lowing two factors led to this result: First, the vibra- tion waves generated by the two EPVL vibrators can separate the stones from the ureter, and can also push the stones forward, thereby reducing the likelihoods of stones incarcerated in the ureter and inflammation; Second, the vibration waves drive the movement of the stones, thereby improving the rate of stone discharge and reducing the occurrence of related complications. In the present analysis, lumbago and dizziness were not found to be necessarily related to whether patients received EPVL treatment; however, the occurrence of these two complications in all experiments was relative- ly small. It was also found that the current efficacy of EPVL treatment has certain defects; as an emerging technolo- gy, the EPVL device has not been widely used in clini- cal practice, and a specific treatment process and spec- ifications have not yet been formed. All patients must drink water before receiving EPVL treatment, but there is no obvious conclusion regarding the specific amount. Additionally, scholars have not yet proposed the best position of the EPVL device during the main treatment period or the method of vibration wave transmission. Moreover, the rotation of the rotating bed allows the patient to assume a high dorsal position to facilitate the discharge of stones, but there is no clear conclusion about which angles of rotation can achieve the best ef- fect. Standardized treatment programs and prospective RCTs involving more centers may be more objective in evaluating this technique. This meta-analysis had several limitations. First, only 7 RCTs were included in this study, and the sample siz- es used for subgroup analysis were small and differed greatly. Second, there were also certain differences be- tween the experimental plans of each group for the ex- ploration of the therapeutic effect of EPVL treatment, thereby leading to the risk of bias. In future related stud- ies, more rigorous prospective RCTs are needed. CONCLUSIONS In summary, the results of the current meta-analysis provided evidence that, as compared with the control group, patients who received EPVL treatment had high- er stone clearance and fewer related complications. The removal rates of stones in the upper/middle/lower calyx and renal pelvis were significantly higher in the inter- vention group, and significant side effects were not re- ported. Therefore, EPVL treatment is an effective and repeatable method for the discharge of residual stones. CONFLICT OF INTERESTS The authors declare that they have no conflicts of in- terest. REFERENCES 1. Moe OW. Kidney stones: pathophysiology and medical management. Lancet. 2006;367:333-44. 2. Farhan M, Nazim SM, Salam B, Ather MH. Prospective evaluation of outcome of percutaneous nephrolithotomy using the ‘STONE’nephrolithometry score: A single- centre experience. Arab journal of urology. 2015;13:264-9. 3. Raja A, Hekmati Z, Joshi HB. 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