Vol 19 No 1 January-February 2022 138 REVIEW Suctioning Versus Traditional Access Sheath in Mini-Percutaneous Nephrolithotomy: A Systematic Review and Meta-analysis Di Chen2, Changsheng Chen3, Yurun Xie3, Zhihua Luo3, Gang Liu1* Purpose: The suctioning access sheath (SAS) is a novel access sheath connected to a negative pressure suction de- vice and absorbs fragments. Some comparative studies have reported SAS with a higher stone-free rate and lower operative time. However, no higher-level evidence was published to support SAS. Hence, this systematic review and meta-analysis aimed to assess the clinical safety and efficacy of SAS versus traditional access sheath (TAS) for the treatment of renal stones in mini-percutaneous nephrolithotomy (MPCNL). Materials and Methods: A systematic review of the literature was conducted using Pubmed, Embase (Ovid), Medline (EBSCO), Cochrane central register of controlled trials, and Sinomed to search comparative studies as recent as December 2020 that assessed the safety and effectiveness of SAS in PCNL. The quality of retrospective case-control studies (RCCs) and randomized controlled trials (RCTs) were evaluated by the Newcastle-Ottawa Scale (NOS) and the Cochrane risk of bias tool, respectively. The Oxford center set up evidence-based medicine was used to assess the level of evidence (LE). Statistical analyses were performed by the comprehensive me- ta-analysis program. Results: Seven studies, with a total of 1655 patients, were included. Compared with the TAS group, the SAS group had a shorter operative time (MD = -17.30; 95%CI:-23.09,-11.51; P < .00001), higher stone-free rate (OR = 2.37;95%CI:1.56,3.61;P < .0001), fewer total complication rate (OR=0.50;95%CI:0.35,0.70; P < .0001), low- er auxiliary procedures rate (OR=0.48;95%CI:0.36,0.64; P<.00001), and lower postoperative fever rate (OR = 0.46;95%CI:0.34,0.62; P < .00001). Conclusion: The SAS can significantly improve MPCNL in the stone-free rate, operative time, and total compli- cation rate, especially for auxiliary procedures and postoperative fever rates. Keywords: suctioning access sheath; mini-percutaneous nephrolithotomy; systematic review; meta-analysis; efficacy; safety INTRODUCTION Urolithiasis is a common urinary disease. With a 10% recurrence rate in one year and 1.7%-14.8% prevalence rates(1,2), the disease brings a severe burden to patients and society. Minimally invasive surgery, such as PCNL, extracorporeal shock wave lithotrip- sy (ESWL), and retrograde intrarenal stone surgery (RIRS), are used to remove stones and relieve obstruc- tion in the clinic. Due to better safety and effectiveness, PCNL is the first-line treatment for larger than 2 cm or complex renal stones(3). However, high renal pelvic pressure and damage still can be a tricky question to PCNL. Many approaches are developed to decrease the compli- cations, including the use of minimally access sheath. According to the access sheath size, PCNL is divided into minimally invasive percutaneous nephrolithotomy (MPCNL) and standard percutaneous nephrolithotomy (SPCNL). With a smaller access sheath, MPCNL has the advantage of lower bleeding, fewer transfusion rate, and shorter hospitalization(4). However, minimally ac- 1The Reproductive Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, Guangxi, China. 2The Nanxishan Hospital of Guangxi Zhuang Autonomous Region, Guilin, 541000, Guangxi, China. 3Department of Urology, People’s Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, Guangxi, China. *Correspondence: The Reproductive Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, Guangxi, China. Email: urology.dr_liu@foxmail.com Received March 2021 & Accepted October 2021 cess sheath is reported with higher renal pelvic pressure and longer operative time, causing a high risk of post- operative urinary infection(5,6). Recently, the application of continuous suctioning systems, such as SAS(7), Swiss LithoClast@(8), Cyberwand(9), reported a lower renal pelvic pressure and less operative time than the stand- ard perfusion system. SAS, retrofitted from a traditional minimally access sheath or a patented sheath, is inex- pensive and cost-effective(10). Keeping the advantage of minimally access sheath, the SAS can connect with a negative pressure aspirator. With the help of negative pressure, fragments and perfusate would be sucked out from patients immediately. Several RCTs have investi- gated the safety and effectiveness of SAS in PCNL. In 2017, a study conducted by Huang et al. reported the SAS group's stone-free rate is 96.7%, while that of the TAS group is 73.6%(P < 0.05) in the treatment of non- staghorn calculi(11). Xu et al. designed a study that in- cluded staghorn calculi cases to determine the operative time between TAS and SAS(12). The result indicated that SAS could significantly improve complication, stone- free rate, and operative time in PCNL. Urology Journal/Vol 19 No. 1/ January-February 2022/ pp. 1-8. [DOI: 10.22037/uj.v18i.6773] Meta-analysis has a high level in evidence-based med- icine and the advantage of overcoming samples' limita- tions from different studies. However, to date, the effec- tiveness and safety of SAS have not still been evaluated by systematic review or meta-analysis. Therefore, our systematic review and meta-analysis was performed to assess the safety and effectiveness between SAS and TAS in MPCNL. MATERIALS AND METHODS The meta-analysis was registered on the Internation- al Prospective Register of Systematic Reviews(13) (PROSPERO, https://www.crd.york.ac.uk/prospero/, ID: CRD42021228513). According to the PRISMA guidelines(14), our perspective protocol included an ob- jective, study search strategy, selection criteria, level of evidence, assessment of quality, data extraction, me- ta-analysis, sensitivity analysis, and publication assess- ment bias. Study search strategy A systematic review of studies, from published stud- ies until December 2020, was performed from the fol- lowing databases: Pubmed, Embase (Ovid), Medline (EBSCO), Cochrane central register of controlled trials, Sinomed. Besides, the references of all related studies were screened. Two authors independently performed the search of studies (Yu-run Xie and Zhi-hua Luo). When there were any disagreements, two previous authors cross-checked and then discussed with a third author (Chang-sheng Chen). MeSH terms were used in each database, and retrieval strategy used sequentially as follows: Table1. Characteristics of the included studies Author Year Period Study type LE Quality of study Sheath size(F) Sample (N) SAS TAS Du et al. (20) 2018 2009-2014 RCT 1b 3a 16-18 311 304 Zhu et al. (10) 2019 2018-2019 RCC 3b 6b 20 256 256 Huang et al. (11) 2016 2011-2013 RCT 1b 4a 16 91 91 Xu et al. (12) 2020 2018 RCT 1b 4a 20 30 30 Lai et al. (18) 2019 2017-2018 RCC 3b 6b 18 75 75 Song et al.(19) 2011 2008-2009 RCT 1b 3a 16 30 30 Lai et al. (7) 2020 2017-2018 RCT 1b 4a 20 38 38 SAS versus TAS in Mini-Percutaneous Nephrolithotomy-Chen et al. Review 2 Figure 1. Study retrieval flow chart SAS suction access sheath, TAS traditional access sheath, RCT randomized controlled trial, RCC retrospective case control study, LE level of evidence, a Using the Cochrane risk of bias tools (score from 0 to 7), b Using the Newcastle-Ottawa Scale (score from 0 to 9) Vol 19 No 1 January-February 2022 138 (1): (((((((((Suctions) OR (Suctioning)) OR (Aspiration, Mechanical)) OR (Aspirations, Mechanical)) OR (Me- chanical Aspiration)) OR (Mechanical Aspirations)) OR (Drainage, Suction)) OR (Drainages, Suction)) OR (Suction Drainage)) OR (Suction Drainages) (2): (((Percutaneous nephroscope) OR (Nephrolithoto- mies, Percutaneous)) OR (Percutaneous Nephrolithoto- mies)) OR (Percutaneous Nephrolithotomy) (3): (1) and (2) Selection criteria Searched studies were eligible if the following selec- tion criteria were met. Inclusion criteria: (1) English language; (2) full text available; (3) Comparative study including RCT or RCC; (4) included renal calculus pa- tients needed the treatment of MPCNL; (5) SAS and TAS used in two groups, respectively. Exclusion cri- teria: (1) included patients with anatomical malforma- tion or coagulation function abnormalities; (2) repeated publication. Quality assessment of eligible studies The Oxford center set up evidence-based medicine was used to assess the LE(15). Furthermore, the NOS(16) and the Cochrane risk of bias tool(17) were applied to assess the quality of RCCs and RCTs, respectively. Two au- thors independently performed this step and compared consistencies (Yu-run Xie and Zhi-hua Luo). Any dis- agreements were resolved by a third author (Chang- sheng Chen). Data extraction Two authors browsed the full text of eligible studies and recorded related data (Di Chen and Chang-sheng Chen). Main outcome indicators were defined as follows:(1) at least three studies reported; (2) measurement or defini- tion was similar. Finally, we extracted selected data as following: name of the first author, year of publication, the period of study, study type, stone burden, sheath size, lithotripter, sample, and main outcome indicators. Meta-analysis The meta-analysis was performed by Review Manager Software (RevMan V.5.2, Cochrane Collaboration, Ox- Author Lithotripter Stone burden Staghorn calculi Outcome indicators SAS TAS Du et al. (20) HL 13.6 ± 5.2b 13.9 ± 4.7b Yes SFR, PFR, APR Zhu et al. (10) HL 15.23 ± 6.67b 14.87 ± 6.32b Yes SFR, PFR, APR, TCR, OT Huang et al. (11) HL 1.67 ± 0.58a 1.51 ± 0.63a No SFR, PFR, APR, OT Xu et al. (12) HL 4.2 ± 1.0a 3.8 ± 1.4a Yes SFR, PFR, APR, TCR, OT Lai et al. (18) HL 6.76 ± 0.22b 6.29 ± 0.34b No SFR, PFR, APR, TCR, OT Song et al. (19) HL 8.57 ± 2.25b 8.65 ± 2.03b No SFR, PFR, APR Lai et al. (7) HL 2.34 ± 0.73a 2.02 ± 0.65a No SFR, PFR, TCR, OT Table 2. Details of stone burden and outcome indicators HL holmium laser, SAS suction access sheath, TAS traditional access sheath, a Stone maximal diameter(cm), b Stone surface area (cm2), SFR stone-free rate, PFR postoperative fever rate, APR auxiliary procedures rate, TCR total complication rate, OT operative time Figure 2. Forest plot of the operative time of the suctioning access sheath (SAS) group and the traditional access sheath (TAS) group SAS versus TAS in Mini-Percutaneous Nephrolithotomy-Chen et al. Vol 19 No 1 January-February 2022 3 ford, UK). Two categorical variables of main outcome indicators, SFR and complication, were calculated as the summary statistic using the pooled odds ratios with 95% confidence intervals (CIs). Due to continuous var- iables, mean differences (MDs) with 95%CI were per- formed for statistical analysis of operative time. With P < .05 considered statistically significant, the Z test was used to determine all the pooled effects. The pooled heterogeneity of statistics was assessed by the Cochrane Chi-squared test and inconsistency(I2). The random-ef- fects model was adopted when the heterogeneity was significant (P < .05 or I2 > 50%). Otherwise, a fixed-ef- fects model was used for the pooled. Subgroup anal- yses and sensitivity analysis was performed to assess the cause of significant heterogeneity. Furthermore, a funnel plot was used to examine publication bias when eligible studies less than ten. RESULTS Characteristics of studies According to the previous search strategy, 206 studies were identified. Then, 113 duplicate studies were ex- cluded. Finally, a total of seven studies(7,10-12,18-20), with 1655 cases, were included in the meta-analysis (Figure 1). The characteristics, level of evidence, and quality assessment of eligible studies are reported in Table 1. Five RCTs and two RCCs were 1b and 3b levels of evidence, respectively. Simultaneously, the quality as- sessment of RCCs was high (NOS: 6 of 9 points). Ta- ble2 exhibits lithotripter, stone burden, and main out- come indicators. Only three eligible studies reporting staghorn calculi cases included. Operative time Five eligible studies(7,10-12,18), three of which were RCTs and two were RCCs, reported operative time (from the insertion of the ureteroscope to the placement of ne- phrostomy tube). With 490 cases in the SAS group and the same cases in the TAS group, the result indicated operative time in the SAS group was shorter than that of the TAS group (MD=-17.3;95%CI: -23.09, -11.51; P < .00001; Figure 2). The result had significant het- erogeneity (P < .0001; I2 = 85%). Stone burden was an important factor affecting operative time. Duo to large size and complex morphology, staghorn stones require more time to remove. Therefore, a subgroup analysis based on stone burden was performed. In the subgroup analysis, two studies were assigned in a staghorn cal- culi group and the other three studies in a non-staghorn calculi group. As shown in Figure 2, the SAS group of staghorn calculi was shorter than that of the TAS group in operative time (MD = -22.21;95%CI: -32.39, -12.03; P < .0001). The non-staghorn calculi subgroup had a similar result (MD = -14.60;95%CI: -17.03, -12.16; P < .0001). Test for subgroup differences was significant (P = .15; I2 = 50.8%). Stone-free rate All eligible studies reported stone-free rate after one session, and the stone-free state was defined as no re- sidual stones > 4 mm evaluated by no-contrast CT or KUB. Five studies informed that the evaluation was performed on postoperative one week. As presented in Figure 3, the SAS group was higher than the TAS group in stone-free rate. (OR=2.37;95%CI:1.56,3.61; P < .0001). However, a subgroup analysis was per- formed due to heterogeneity (P = .06; I2 = 51%). Stone burden was a factor affecting stone-free rate, suggest- ing may affects heterogeneity in our meta-analysis. In subgroup analysis, three studies in the staghorn calculi group and four in the non-staghorn calculi group. With low heterogeneity (P = .39; I2 = 0%) in the staghorn calculi subgroup, the SAS group had a higher stone- free rate (OR=1.63;95%CI:1.25,2.13; P = .0003). The non-staghorn calculi subgroup also had a similar result (OR=3.75;95%CI:2.00,7.06; P < .0001). Test for sub- group differences was significant (P = .02; I2 = 82.3%). Figure 3. Forest plot of the stone-free rate of the suctioning access sheath (SAS) group and the traditional access sheath (TAS) group SAS versus TAS in Mini-Percutaneous Nephrolithotomy-Chen et al. Review 4 Vol 19 No 1 January-February 2022 138 Total complications rate Four eligible studies reported total complications rate(7,10,12,18). Modified Clavien classification was used to evaluate total complications in three studies. One study assessed total complication by the Clavien grade clas- sification. The total complication rate between the SAS group and the TAS group is presented in Figure 4. Com- pared with the TAS group, the SAS group had a lower total complication rate (OR=0.50;95%CI:0.35,0.70; P < .0001). Furthermore, the heterogeneity was low (P = .75; I2 = 0%). In subgroup analysis, two studies in the staghorn calculi group and two in the non-staghorn cal- culi group. With low heterogeneity (P > .05; I2 > 50%) and subgroup differences ( P = .97; I2 = 0%), two sub- group results reported that the SAS group had a lower total complication rate (P < .001). Auxiliary procedures rate Auxiliary procedures, such as shockwave lithotripsy, 2nd PCNL, and retrograde intrarenal stone surgery, were reported in six eligible studies(10-12,18-20). In the me- ta-analysis, the auxiliary procedures rate was signifi- cantly lower in the SAS group than the TAS group (OR = 0.48;95%CI :0.36,0.64; P < .00001; Fig.5). The result exhibited a low heterogeneity (P = .15; I2 = 39%). In Figure 5. Forest plot of the auxiliary procedures rate of the suctioning access sheath (SAS) group and the traditional access sheath (TAS) group Figure 4. Forest plot of the total complication rate of the suctioning access sheath (SAS) group and the traditional access sheath (TAS) group SAS versus TAS in Mini-Percutaneous Nephrolithotomy-Chen et al. Vol 19 No 1 January-February 2022 5 subgroup analysis, three studies in the staghorn calculi group and three in the non-staghorn calculi group. With low heterogeneity (P > .05; I2 < 50%) and significant subgroup differences ( P = .03; I2=79%), two subgroup results reported that the SAS group had a lower auxilia- ry procedures rate (P < .001). Postoperative fever rate All eligible studies reported postoperative fever. Six studies defined postoperative fever as postoperative temperature > 37.5℃. As presented in Figure 6, the postoperative fever rate was found to be significantly lower in the SAS group than the TAS group(OR = 0.46; 95%CI:0.34,0.62 ;P < .00001).The result exhibited a low heterogeneity (P = .76; I2 = 0%). Notably, subgroup analysis also exhibited similar results. Sensitivity analysis and bias of publication To test the stability of the result, we performed a sen- sitivity analysis with an article-by-article culling meth- od. After the research by Zhu et al. was excluded in operative time, the I2 value changed from 85% to 0%. Simultaneously, the I2 value of stone-free rate changed from 51% to 0% by Huang et al. was excluded. While the result of operative time and stone-free rate was still stable. Therefore, the analysis suggested that both stud- ies were the major cause of the heterogeneity, and our result is convincing. However, the funnel plot, used to assess publication bias, was unbalanced and indicated some publication bias. DISCUSSION Higher safety and effectiveness are still the goals for urologists to improve PCNL. Although MPCNL has the advantage of being minimally invasive, the increased operative time and renal pelvic pressure > 30mmhg are high-risk postoperative infection factors(21,22). Therefore, accelerated suctional speed of perfusate and fragments may be a rational approach to reduce complications. In 2011, Song et al.’s RCT firstly reported a patented SAS, which can connect to a negative aspirator and keep a 16 F size(19). The result indicated that patients in the SAS group had a higher stone-free rate than the TAS group (stone-free rate: 90% vs. 73.3%; P < .05). However, the SAS was not further investigated and used in clinical practice widely. Recently, SAS has gradually been concerned and used in clinics since other simplified or purchasable SAS re- ported(23), such as ClearPetra(7) and homemade SAS(10). Many scholars have conducted related clinical studies. In 2019, Lai et al. performed a feasibility study that re- ported the ClearPetra with the function of suction and store fragments(18). Next year, Xu et al. conducted an RCT that included staghorn stones to assess the safety and effectiveness of ClearPetra(12). The result suggested that compared with TAS, ClearPetra can significant- ly improve renal pelvic pressure, stone-free rate, and complications in MPCNL. Similarly, Zhu et al. report- ed a simplified and homemade SAS in a case-matched comparative study, which had a lower operative time and lower complication rate(10). However, to date, the SAS has not been evaluated by a systematic review or meta-analysis. Stone-free rate and operative time are valid indicators to assess the effectiveness of PCNL. Because of the high recurrence rate in fragments > 4mm(24), fragments < 4mm are regarded as clinically insignificant residu- al fragments (CIRFS) and the symbol of stone-free(25). However, the removal of renal stone fragments still re- mains a tricky problem. Clinically, graspers or baskets were commonly used to remove fragments, but repet- itive mechanical operation will cause mucosa damage and is time consuming. In order to improve fragments removal, several modalities have been proposed. Pan- ah et al. reported a technique to flush out renal stone fragments by refluxed infusion(26). Subsequently, Kati Figure 6. Forest plot of the postoperative fever rate of the suctioning access sheath (SAS) group and the traditional access sheath (TAS) group SAS versus TAS in Mini-Percutaneous Nephrolithotomy-Chen et al. Review 6 Vol 19 No 1 January-February 2022 138 et al. performed a comparative study between aspiration method and irrigation method(27). They found that stone- free rate was higher in aspiration method, containing the advantage of high efficiency and convenience. In our study, the stone-free rate and operative time were better in the SAS group. The result may relate with the characteristic of SAS. With the advantage of continu- ous negative pressure suction, SAS can gather around fragments and then suck out, avoiding escape to other renal calyces. Due to the gravity, the lower pole calyx is a common and tricky position for deposited fragments. SAS, with continuous suction, may improve the treat- ment of fragments deposited in the lower pole calyx. Du et al. performed a multicenter RCT and reported a sim- ilar opinion that SAS could immobilize stone and limit the movement of fragments, causing a higher stone- free rate and less operative time(20). Furthermore, SAS may reduce the necessity of powder fragments. Several studies revealed that fragments < 5mm could be sucked out(19). Lai et al. reported that fragments with a maxi- mum diameter of 6.3mm can be aspirate by a 20F SAS, which decreases operative time in shattering stone(7). Moreover, when the holmium laser smashes stone, SAS can accelerate perfusate mobile speed and keep a clear visual field, which is an important cause of operative time shorted. Although our result had significant het- erogeneity, subgroup analysis and sensitivity analysis were performed and found the cause of heterogeneity. After reducing the heterogeneity, our result still indicat- ed that the SAS group had a higher stone-free rate and less operative time than the TAS group. When evaluating the safety of PCNL, the postoperative complication rate is a credible indicator. Currently, the Modified Clavien-Dindo system is a rational and val- idated complication classification system widely used to assess urology surgery complications(28). Postoper- ative fever is a grade I complication in the Modified Clavien-Dindo system. Although only four eligible studies reported total complications assessed by the Clavien-Dindo system, all seven included studies re- ported postoperative fever risk. The present result suggested that the SAS group showed much less total complication rate than the TAS group, especially in postoperative fever and auxiliary procedures. These results may be the following causes: (1) A lower inter- operative renal pelvis pressure in the SAS group. High renal pelvis pressure contributes to absorbed bacterial endotoxin and damages the collecting system, causing high operative fever and even urinary tract infection. Zhong et al. informed that high RPP (> 30mmhg) and accumulated time of high RPP (> 50 s) are risk factors of postoperative fever(29). Xu et al.’s RCT assessed the renal pelvis pressure of different puncture poles and pe- riod reported that SAS can significantly decrease renal pelvis pressure and pressure-related complications(12). Several studies reported operative time is a dependent risk factor of postoperative fever or urosepsis(22,29). With a continuous negative pressure state, SAS accelerated the speed of fragments removal, decreased operative time. Additionally, because the heterogeneity of total complication rate, postoperative fever rate, and auxilia- ry procedures rate is low, we achieved a convincing re- sult that the SAS can improve complications compared with TAS. Our study also had some limitations:(1) Even if we had found the cause of heterogeneity in our result, the defi- nition of some outcomes among included studies was not completely consistent or clear, causing the increase of heterogeneity.(2) Although two RCCs included in the study were of high quality, more related RCTs are need- ed to be included.(3) Because all included studies were independent studies and came from the same country, included high-quality RCT from different countries may improve credibility further.(4) All included studies in our research used holmium laser lithotripsy. Differ- ent lithotripsy techniques may impact the effectiveness and safety of PCNL due to crushing mechanisms dif- ferences(30), and thus our conclusions may not apply to other types of lithotripsy. CONCLUSIONS Above all, our study results found that compared with the TAS group, patients in the SAS group had higher stone-free rate, less operative time, lower total compli- cation rate, lower postoperative fever rate, and lower auxiliary procedure rate. Therefore, SAS is a safe and effective method in MPCNL. COMPETING INTERESTS The authors declare that they have no competing inter- ests REFERENCES 1. Wilkinson H. Clinical investigation and management of patients with renal stones. Ann Clin Biochem. 2001;38:180-7. 2. Viljoen A, Chaudhry R, Bycroft J. Renal stones. Ann Clin Biochem. 2019;56:15-27. 3. Yang YH, Wen YC, Chen KC, Chen C. Ultrasound-guided versus fluoroscopy-guided percutaneous nephrolithotomy: a systematic review and meta-analysis. World J Urol. 2019;37:777-88. 4. Zhu W, Liu Y, Liu L, et al. Minimally invasive versus standard percutaneous nephrolithotomy: a meta-analysis. Urolithiasis. 2015;43:563-70. 5. Wu C, Hua LX, Zhang JZ, Zhou XR, Zhong W, Ni HD. Comparison of renal pelvic pressure and postoperative fever incidence between standard- and mini-tract percutaneous nephrolithotomy. Kaohsiung J Med Sci. 2017;33:36-43. 6. Feng D, Zeng X, Han P, Wei X. Comparison of intrarenal pelvic pressure and postoperative fever between standard- and mini-tract percutaneous nephrolithotomy: a systematic review and meta-analysis of randomized controlled trials. Transl Androl Urol. 2020;9:1159-66. 7. Lai D, Xu W, Chen M, et al. Minimally Invasive Percutaneous Nephrolithotomy with a Novel Vacuum-assisted Access Sheath for obstructive calculous pyonephrosis. A Randomized Study. Urol J. 2020;17:474-9. 8. Nottingham CU, Large T, Cobb K, et al. Initial Clinical Experience with Swiss LithoClast Trilogy During Percutaneous Nephrolithotomy. J Endourol. 2020;34:151-5. 9. York NE, Borofsky MS, Chew BH, et al. Randomized Controlled Trial Comparing Three Different Modalities of Lithotrites for Intracorporeal Lithotripsy in Percutaneous SAS versus TAS in Mini-Percutaneous Nephrolithotomy-Chen et al. Vol 19 No 1 January-February 2022 7 Nephrolithotomy. J Endourol. 2017;31:1145- 51. 10. Zhu Z, Cui Y, Zeng H, et al. Suctioning versus traditional minimally invasive percutaneous nephrolithotomy to treat renal staghorn calculi: A case-matched comparative study. Int J Surg. 2019;72:85-90. 11. Huang J, Song L, Xie D, et al. A Randomized Study of Minimally Invasive Percutaneous Nephrolithotomy (MPCNL) with the aid of a patented suctioning sheath in the treatment of renal calculus complicated by pyonephrosis by one surgery. BMC Urol. 2016;16:71. 12. Xu G, Liang J, He Y, et al. Comparison of two different minimally invasive percutaneous nephrostomy sheaths for the treatment of staghorn stones. BJU Int. 2020;125:898-904. 13. Harris JD, Quatman CE, Manring MM, Siston RA, Flanigan DC. How to write a systematic review. Am J Sports Med. 2014;42:2761-8. 14. Liberati A, Altman DG, Tetzlaff J, et al. The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration. Bmj. 2009;339:b2700. 15. Kaefer M, Castagnetti M, Herbst K, et al. Evidence-based medicine III: level of evidence. J Pediatr Urol. 2019;15:407-8. 16. Norris JM, Simpson BS, Ball R, et al. A Modified Newcastle-Ottawa Scale for Assessment of Study Quality in Genetic Urological Research. Eur Urol. 2020. 17. Higgins JP, Altman DG, Gøtzsche PC, et al. The Cochrane Collaboration's tool for assessing risk of bias in randomised trials. Bmj. 2011;343:d5928. 18. Lai D, Chen M, Sheng M, et al. Use of a Novel Vacuum-Assisted Access Sheath in Minimally Invasive Percutaneous Nephrolithotomy: A Feasibility Study. J Endourol. 2020;34:339- 44. 19. Song L, Chen Z, Liu T, et al. The application of a patented system to minimally invasive percutaneous nephrolithotomy. J Endourol. 2011;25:1281-6. 20. Du C, Song L, Wu X, et al. Suctioning Minimally Invasive Percutaneous Nephrolithotomy with a Patented System Is Effective to Treat Renal Staghorn Calculi: A Prospective Multicenter Study. Urol Int. 2018;101:143-9. 21. Omar M, Noble M, Sivalingam S, et al. Systemic Inflammatory Response Syndrome after Percutaneous Nephrolithotomy: A Randomized Single-Blind Clinical Trial Evaluating the Impact of Irrigation Pressure. J Urol. 2016;196:109-14. 22. Zhu L, Jiang R, Pei L, Li X, Kong X, Wang X. Risk factors for the fever after percutaneous nephrolithotomy: a retrospective analysis. Transl Androl Urol. 2020;9:1262-9. 23. Gökce M, Karaburun MC, Babayiğit M, et al. Effect of Active Aspiration and Sheath Location on Intrapelvic Pressure During Miniaturized Percutaneous Nephrolithotomy. Urology. 2021. 24. Chew BH, Brotherhood HL, Sur RL, et al. Natural History, Complications and Re- Intervention Rates of Asymptomatic Residual Stone Fragments after Ureteroscopy: a Report from the EDGE Research Consortium. J Urol. 2016;195:982-6. 25. Türk C, Petřík A, Sarica K, et al. EAU Guidelines on Interventional Treatment for Urolithiasis. Eur Urol. 2016;69:475-82. 26. Panah A, Masood J, Zaman F, Papatsoris AG, El-Husseiny T, Buchholz N. A technique to flush out renal stone fragments during percutaneous nephrolithotomy. J Endourol. 2009;23:5-6. 27. Kati B, Pelit ES, Yagmur I, Akin Y, Ciftci H, Yeni E. Which way is best for stone fragments and dust extraction during percutaneous nephrolithotomy. Urolithiasis. 2018;46:297- 302. 28. Singh AK, Shukla PK, Khan SW, Rathee VS, Dwivedi US, Trivedi S. Using the Modified Clavien Grading System to Classify Complications of Percutaneous Nephrolithotomy. Curr Urol. 2018;11:79-84. 29. Zhong W, Zeng G, Wu K, Li X, Chen W, Yang H. Does a smaller tract in percutaneous nephrolithotomy contribute to high renal pelvic pressure and postoperative fever? J Endourol. 2008;22:2147-51. 30. Radfar MH, Basiri A, Nouralizadeh A, et al. Comparing the Efficacy and Safety of Ultrasonic Versus Pneumatic Lithotripsy in Percutaneous Nephrolithotomy: A Randomized Clinical Trial. Eur Urol Focus. 2017;3:82-8. SAS versus TAS in Mini-Percutaneous Nephrolithotomy-Chen et al. Review 8