Stesura Seveso Archivio Italiano di Urologia e Andrologia 2024; 96(4):12944 1 META-ANALYSIS tion (1). Its prevalence varies worldwide, starting from 1- 5% in Asia, 5-9% in Europe, and 7-13% in North America (2). The global morbidity and disability-adjusted life years (DALYs) of nephrolithiasis increased substan- tially between 1990 and 2019 (3). The majority of kidney stones are composed of calcium, primarily in the form of calcium oxalate or calcium phosphate stones (2). Nephrolithiasis is often symptomatic (4). Percutaneous nephrolithotomy (PCNL) is the primary treatment in patients with symptomatic nephrolithiasis larger than 2 cm (5). Over time, PCNL has been through many alterations in patient positioning. The first ever PCNL was done by Fernström et al. in prone position, back in 1976. The prone position was believed to be safe- ly avoiding vital organs, such as the colon (6). Later, the first report of supine PCNL was introduced by Valdivia et al. in 1990 (7) and further elaborated in 1998 (8). Since then, the supine position has undergone variable modifi- cations. This includes the flank roll position, Galdakao- modified Valdivia position, crossed-leg supine position, complete supine position, and the most recent Barts FFMS position (9). All of them have been reported to decrease the duration of PCNL procedures by eliminating the need for patient repositioning and allowing quick air- way access (10). Barts flank-free modified supine (FFMS) position is a newly enhanced version of the traditional supine position, with better access to the kidney (10). It offers several advan- tages compared to the prone position, including easier fluoroscopy access, more comfortable patient positioning, simpler tract dilation, reduced kidney pressure, improved fragment clearance, and easier transition to RIRS (11). Given these potential benefits, it is crucial to determine whether Barts FFMS is superior to the prone position in terms of clinical outcomes. This study aims to compare the Barts FFMS and prone positions in PCNL, focusing on key clinical outcomes such as stone-free rates, complications, and surgery dura- tion. By identifying the optimal patient positioning for PCNL, this study seeks to contribute to the improvement of patient care and surgical efficiency in the treatment of nephrolithiasis. Introduction: Percutaneous Nephrolithotomy (PCNL) has been performed in various posi- tions, including prone position and several modifications of supine position. The Barts flank-free modified supine (FFMS) position is a newly enhanced version of the supine positions. This study aims to compare the outcomes of Barts FFMS and prone position in PCNL. Methods: This study followed PRISMA 2020 guideline and was registered to PROSPERO CRD42024530426. Comprehensive search in PubMed, Sciencedirect, and Scopus was conducted until May 2024. Stone-free rates, complications, surgery dura- tion, fluoroscopy duration, use of nephrostomy, and length of stay were collected. Data were analyzed using RevMan 5.4. Results: A total of 4 studies were included in this review. There was no significant difference in stone-free rates between Barts FFMS and prone positions (OR = 1.12, 95% CI 0.64-1.95, p = 0.70). There were no significant difference in incidence of fever (OR = 0.91, 95% CI 0.38-2.18, p = 0.84), need for blood transfu- sion (OR = 0.46, 95% CI 0.11-1.88, p = 0.28), and urine leakage (OR = 0.41, 95% CI 0.16-1.05, p = 0.06). The surgery duration was significantly shorter in Barts FFMS position than in prone position (MD = -15.48, 95% CI [(-26.42)-(-4.55)], p = 0.006). There was no significant difference in patients requiring nephrostomy (OR = 0.19, 95% CI 0.01-3.75, p = 0.28). There were no significant difference in fluoroscopy duration (MD = 0.27, 95% CI [(-6.85)-7.40], p = 0.94) and the length of hospital stay (MD = -0.20, 95% CI [(-0.74)-0.33], p = 0.46). Conclusions: The surgery duration was significantly shorter in Barts FFMS position than in prone position. There were no sig- nificant differences regarding stone-free rates, complications, fluoroscopy duration, use of nephrostomy, and length of hospital stay. This indicates that neither Barts FFMS nor prone position is superior, and the choice should be based on the surgeon's preference and the patient's clinical status. KEY WORDS: Barts; Flank-free; Supine; Prone; PCNL. Submitted 19 August 2024; Accepted 31 August 2024 INTRODUCTION Nephrolithiasis is among the most prevalent urological conditions, impacting around 12% of the global popula- Barts flank-free modified supine position vs prone position in percutaneous nephrolithotomy: Systematic review and meta analysis I Gede Yogi Prema Ananda 1, Kadek Budi Santosa 1, 2, I Wayan Yudiana 1, 2, Pande Made Wisnu Tirtayasa 1, 3, Ida Bagus Putra Pramana 1, 3, Nyoman Gede Prayudi 1, 2, Gede Wirya Kusuma Duarsa 1, 2 1 Department of Urology, Faculty of Medicine, Universitas Udayana, Denpasar, Bali, Indonesia; 2 Prof. Dr. I.G.N.G. Ngoerah Hospital, Denpasar, Bali, Indonesia; 3 Universitas Udayana Teaching Hospital, Badung, Bali, Indonesia. DOI: 10.4081/aiua.2024.12944 Summary Archivio Italiano di Urologia e Andrologia 2024; 96(4):12944 I Gede Yogi Prema Ananda, K. Budi Santosa, I W. Yudiana, et al. 2 METHODS Study design This systematic review and meta-analysis followed PRIS- MA 2020 guidelines and was registered to PROSPERO CRD42024530426. Search strategy Comprehensive search by the authors in scientific data- bases such as PubMed, Sciencedirect, and Scopus was con- ducted until May 2024. The keywords used were "PCNL" AND ("flank-free" OR "Barts"). The authors engaged in discussions to settle any disagreements. Eligibility criteria Inclusion criteria cover studies in English, RCT or cohort studies, and adult patients who had undergone standard PCNL in Barts FFMS compared to prone position. The definition of Barts FFMS position included in this study is a supine position with a 15° tilt of the ipsilateral flank, achieved by placing a 3-liter saline bag under the rib cage and a gel pad under the pelvis, thus creating the 'flank- free' position (8). Stone-free rates, postoperative complications, and dura- tion of surgery were the expected pri- mary outcomes, while fluoroscopy duration, need for nephrostomy, and length of stay were chosen as second- ary outcomes. Exclusion criteria cover non-English articles, study designs other than RCTs or prospective stud- ies, non-standard PCNL procedures, and PCNL positions other than Barts FFMS and prone position. Data extraction Information was systematically collect- ed using a structured format as first author, publication year, study design, sample size, age, body mass index (BMI), stone size, stone-free rates, complica- tions, duration of surgery, duration of fluoroscopy, number of patients need- ing nephrostomy, and length of hospi- tal stay. Data analysis The analysis for this study was con- ducted using Review Manager version 5.4 (The Cochrane Collaboration, The Nordic Cochrane Centre, Copenhagen, Denmark). For continuous data, the Mean Difference (MD) was utilized, while dichotomous data were analyzed using the Odds Ratio (OR). Meta-analy- sis was performed when two or more studies provided the same type of data. To assess the heterogeneity among the included studies, Cochran’s Q and I² statistics were employed. A fixed- effects model was used when there was statistical homogeneity (defined as p- value > 0.1 and I² < 50%). In cases where heterogeneity was present (p-value ≤ 0.1 or I² ≥ 50%), a random-effects model was applied. Statistical significance was deter- mined with a threshold of p < 0.05. Quality appraisal To assess the selected studies, we utilized two different tools. We utilized two different tools: the Jadad score for randomized controlled trials (RCTs) and the Newcastle- Ottawa Scale (NOS) for cohort studies. If any discrepan- cies arose in bias assessments or justifications, they will be resolved through discussions among the authors until a consensus was reached. RESULTS Study selection The search yielded 263 results, with 231 records removed due to duplicates and irrelevance. After this removal, 32 potentially relevant articles remained. A thorough examination of the full texts resulted in 4 stud- ies meeting the inclusion criteria for this review. The process is illustrated in the PRISMA flow chart (Figure 1). Figure 1. PRISMA flowchart. Archivio Italiano di Urologia e Andrologia 2024; 96(4):12944 3 Barts flank-free modified supine vs prone position in PCNL Study assessment Two RCTs were included, assessed using the Jadad score and classified as poor quality. Two cohort studies were assessed using the Newcastle-Ottawa Scale, all rated as good quality. The assessment details are presented in Table 1. Study characteristics There were 4 studies with a total of 228 PCNL patients operated in the Barts FFMS position and 285 patients in the prone position. The data in Table 2 provides a summary of the subject's baseline characteristics. From the 4 studies, only 3 of them showed proper data to account for the mean age of the patients. One study by Zanaty et al. lacked the standard deviation (SD) in mean age data. The baseline characteristics such as the sample size, mean age, BMI, stone size, stone-free rate, the defi- nition of stone-free status, and follow up time were avail- able in Table 2. Stone-free rates Based on the forest plot presented in Figure 2, which included all 4 studies, there was no significant difference in the stone-free rate between Barts FFMS and the prone position (OR = 1.12, 95% CI 0.64-1.95, p = 0.70). Complications (Clavien-Dindo) Fever (Clavien-Dindo Grade 1) All studies reported fever as a postoperative complication. Figure 3 indicates that the incidence of fever did not dif- fer significantly between Barts FFMS and the prone posi- tion (OR = 0.91, 95% CI 0.38-2.18, p = 0.84). Blood loss requiring transfusion (Clavien-Dindo Grade 2) Only 3 studies reported blood transfusion. Forest plot in Figure 4 demonstrates that there was no significant difference in the incidence of blood loss requiring transfusion between patients in the Barts FFMS and prone positions (OR = 0.46, 95% CI 0.11-1.88, p = 0.28). Urine leakage (Clavien-Dindo Grade 3) Figure 5 illustrates that the incidence of urine leakage was not significantly different between the Barts FFMS and prone position groups, as shown in the Forest plot of 3 studies (OR = 0.41, 95% CI 0.16-1.05, p = 0.06). Surgery duration The duration of surgery was significantly shorter in Barts Table 1. Assessment of the studies included. Author Study design Assessment Jadad score Newcastle-Ottawa scale Mulay et al., 2022 (12) RCT 1 - Míçooğullari et al., 2021 (13) Cohort - 7 Sohail et al., 2017 (14) Cohort - 7 Zanaty et al., 2022 (15) RCT 2 - Figure 2. Stone-free rates. Table 2. Baseline characteristics of the studies included. Study PCNL Sample size Mean age BMI Stone size Stone-free rate Definition of Follow-up position (n) (years) (kg/m2) (cm) (%) stone-free status time Mulay et al. (2022) Barts FFMS 50 40.16 N/A 2.43 ± 1.23 96 Residual stones < 4 mm 1 month Prone 50 42.80 2.6 ± 1.23 94 Zanaty et al. (2022) Barts FFMS 30 47.40 ± 7.89 32.55 ± 8.98 4.56 ± 1.51 80 N/A N/A Prone 30 47.67 ± 8.82 31.21 ± 5.48 4.05 ± 1.21 90 Sohail et al. (2017) Barts FFMS 96 38.9 ± 10.1 27.9 ± 7.2 2.99 ± 1.26 85 -No residual stones, 1-3 months Prone 101 45.2 ± 9.5 28.7 ± 6.5 2.97 ± 1.51 79 or -Residual stones < 5 mm Míçooğullari et al. (2021) Barts FFMS 52 43.9 ± 16.2 24.4 ± 2.9 3.21 ± 0.73 92 Residual stones < 3 mm 1 month Prone 104 40.8 ± 14.6 24.8 ± 2.9 3.27 ± 0.82 94 Archivio Italiano di Urologia e Andrologia 2024; 96(4):12944 I Gede Yogi Prema Ananda, K. Budi Santosa, I W. Yudiana, et al. 4 FFMS position than in prone position, as indicated in Figure 6 (MD = -15.48, 95% CI [(-26.42)-(-4.55)], p = 0.006). It also showed the studies were heterogeneous. Use of nephrostomy In Figure 7, the forest plot of 3 studies displayed that the use of nephrostomy after PCNL did not differ significant- Figure 4. Blood loss requiring transfusion. Figure 5. Urine leakage. Figure 6. Duration of surgery. Figure 3. Fever. Archivio Italiano di Urologia e Andrologia 2024; 96(4):12944 5 Barts flank-free modified supine vs prone position in PCNL ly in Barts FFMS and prone position (OR = 0.19, 95% CI 0.01-3.75, p = 0.28). The studies were heterogeneous. Fluoroscopy duration Only 2 studies reported the duration of fluoroscopy used in PCNL, and they were heterogeneous. As shown in Figure 8, the duration of fluoroscopy did not significant- ly differ between the Barts FFMS and prone position groups (MD = 0.27, 95% CI [(-6.85)-7.40], p = 0.94). Length of hospital stay The included studies in this outcome were heterogeneous. There was no significant difference between patients in the Barts FFMS and prone positions, as shown in Figure 9 (MD = -0.20, 95% CI [(-0.74)-0.33], p = 0.46). DISCUSSION When choosing between the Barts FFMS and prone posi- tions, it is important to note that all supine positions, regardless of the modification, offer several advantages over the prone position. These include easier positioning for anesthesia, reduced risk of nervous system injury, and suitability for patients with comorbidities such as cardio- vascular disease, risk of infection, and obesity (16). Additionally, the total cost of supine PCNL is lower than that of prone PCNL, due to savings on surgical equip- ment and anesthesia expenses (17). To determine whether the Barts FFMS or prone position is superior, this review focused on stone-free rates, compli- cations, and surgery duration as primary outcomes. The stone-free rates were not significantly different between the Barts FFMS and prone positions. While a meta-analysis by Birowo et al. (18) found higher stone- free rates for supine positions in general, Li et al. (19) reported no significant difference between supine and prone positions. Complications were classified using the Clavien-Dindo system: fever as grade 1, blood loss requiring transfusion as grade 2, and urine leakage as grade 3. The incidences of fever, transfusion due to blood loss, and urine leakage Figure 8. Duration of fluoroscopy. Figure 9. Length of hospital stay. Figure 7. Nephrostomy. Archivio Italiano di Urologia e Andrologia 2024; 96(4):12944 I Gede Yogi Prema Ananda, K. Budi Santosa, I W. Yudiana, et al. 6 were not significantly different between the Barts FFMS and prone positions. However, Li et al. (19) found no sig- nificant difference in complication rates between supine and prone positions, while Birowo et al. (18) reported sig- nificantly lower major complications in supine positions. These discrepancies may be due to inconsistencies in out- come reporting, as not all studies used the Clavien-Dindo classification. In this review, the duration of PCNL was significantly shorter in the Barts FFMS position compared to the prone position. This aligns with Li et al. (19), who also found shorter durations in supine positions, but contrasts with Birowo et al. (18) who reported no significant difference. Literature suggests that supine positions should reduce operation time by eliminating the need for patient reposi- tioning and allowing quick airway access (10). Additionally, supine positions facilitate easier anesthesia, further shortening the duration of surgery (16). The insertion of a nephrostomy tube after PCNL remains as a standard procedure. It served as drainage, a means to tamponade bleeding after surgery, and an access for a sec- ond exploration if necessary (20). In this review, the use of nephrostomy was reported in three articles and showed no significant difference between the Barts FFMS and prone positions. The use of fluoroscopy is a crucial step in PCNL, allow- ing urologists to guide the needle to a safe location. The imaging helps them to navigate into Brodel’s line of bloodless incision, minimizing the probability of bleeding (21). Fluoroscopy duration was reported in only two studies in this review, showing no significant difference between Barts FFMS and prone patients. In this study, the length of hospital stay did not signifi- cantly differ between the Barts FFMS and prone posi- tions. This is consistent with meta-analyses by Birowo et al. (18) and Li et al. (19). This review article provides valuable information to assist surgeons in choosing between the two positions. However, this study has limitations, including a small number of included studies, inconsistencies in outcome reporting, and high heterogeneity in some outcomes. Future research should explore the cost-benefit analysis and potential advantages of the Barts FFMS position to optimize PCNL procedures. CONCLUSIONS The surgery duration was significantly shorter in Barts FFMS position than in prone position. There were no sig- nificant differences regarding stone-free rates, complica- tions, fluoroscopy duration, use of nephrostomy, and length of hospital stay. Overall, the Barts FFMS position was not superior to the prone position. It offers a viable alternative to the prone position in PCNL, with no significant differences in clin- ical outcomes. Therefore, the choice of patient position should be based on the surgeon's preference and the patient's clinical condition. ACKNOWLEDGMENTS We would like to thank all the staff at the Department of Surgery, Urology Division, Prof. Dr. I.G.N.G Ngoerah General Hospital for their support. REFERENCES 1. Alelign T, Petros B. Kidney Stone Disease: An Update on Current Concepts. Adv Urol. 2018; 2018:3068365. 2. 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Correspondence I Gede Yogi Prema Ananda (Corresponding Author) yogiprema16@gmail.com Department of Urology, Faculty of Medicine, Universitas Udayana, Denpasar, Bali, Indonesia Kadek Budi Santosa busanbsa@gmail.com I Wayan Yudiana yanyud@yahoo.com Nyoman Gede Prayudi prayudi_blonx@yahoo.com Gede Wirya Kusuma Duarsa gwkduarsa@yahoo.com Prof. Dr. I.G.N.G. Ngoerah Hospital, Denpasar, Bali, Indonesia Pande Made Wisnu Tirtayasa wisnu.tirtayasa@gmail.com Ida Bagus Putra Pramana bagusputra@unud.ac.id Universitas Udayana Teaching Hospital, Badung, Bali, Indonesia Conflict of interest: The authors declare no potential conflict of interest.