Stesura Seveso Archivio Italiano di Urologia e Andrologia 2024; 96(3):12617 1 ORIGINAL PAPER dence of KSs is influenced by multiple factors, including environmental factors, gender, race, geographical location, occupation, exposure to hot climates, family history, unhealthy diet, obesity, smoking, alcohol consumption, and low fluid intake (5). Additionally, comorbid metabolic disorders, such as hypertension, diabetes mellitus, cardio- vascular disease, and chronic kidney disease can be associ- ated with an elevated risk (3, 4, 6, 7). The symptoms of KSs exhibit variability based on their location—whether within the kidney, ureter, or urinary bladder (8). Common sites for stone dislodgement include the vesicoureteric junction, mid-ureter, and pelvoureteric junction (9). Clinical presen- tations encompass renal colic and flank pain, often accom- panied by gross hematuria, a burning sensation during uri- nation, nausea, vomiting, and fever (9-11). Over the last three decades, there have been notable advancements in KS treatment. Currently, treatment options include minimally invasive methods such as extracorporeal shock wave lithotrip- sy (ESWL), percutaneous nephrolithotomy (PCNL), and retro- grade intrarenal surgery (RIRS), as opposed to conventional open surgery (12). The applications of RIRS in treating KSs have expanded significantly due to recent advances in endoscopic technology (13). Although the efficacy of flexi- ble ureterorenoscopy (URS) in managing solitary KS is wide- ly acknowledged in the literature, its effectiveness in treat- ing multiple stones has scarcely been investigated (14). The present study aims to assess the effectiveness and safety of RIRS utilizing flexible URS and laser lithotripsy in the man- agement of multiple KSs. METHODS Setting and design This single-group cohort study was carried out on patients with multiple KSs who underwent treatment with RIRS with flexible URS and laser lithotripsy at a sin- gle center between September 2020 and July 2023. The Iraqi Council for Medical Specializations granted ethical approval for the study. Patients underwent comprehen- sive counseling concerning various treatment approaches, the risk of complications, and the potential necessity for Introduction: While the efficacy of flexible ureterorenoscopy (URS) in managing solitary kidney stones (KSs) is widely acknowledged, its effectiveness in treating multiple stones has scarcely been investigated. This study aims to assess the effectiveness and safety of retrograde intrarenal surgery (RIRS) utilizing flexible URS and laser lithotripsy in the management of multiple KSs. Methods: This study was a single-group cohort study conducted on patients with multiple KSs who underwent treatment with RIRS using flexible URS and laser lithotripsy. Stone-free status was considered as the lack of residual stone fragments or any residual stone of any size. The first follow-up appointment was arranged 3-4 weeks following the procedure. If significant resid- ual stones were present, patients underwent reintervention with- in 2-4 weeks. Results: A total of 110 patients with multiple KSs were included. The mean stone burden was 27.5 ± 7.9 mm, and the mean dura- tion of the operation was 54.9 ± 19.7 minutes. Seven cases (6.3%) experienced intraoperative complications, while postop- erative complications were found in eight cases (7.3%). After four weeks, a stone-free rate (SFR) was documented in 80.9% of the cases, and this rate increased to 93.6% after three months. The SFR after three months was significant with Guy’s stone score (p < 0.001); however, it did not reach a significant level with any other parameters. Conclusions: The RIRS with flexible URS may be an effective and potentially safe procedure for treating multiple KSs. It may yield a favorable SFR with an acceptable complication rate. KEY WORDS: Kidney stone; Urinary tract; Retrograde intrarenal surgery; Ureterorenoscopy; Nephrolithiasis. Submitted 29 April 2024; Accepted 4 July 2024 INTRODUCTION Nephrolithiasis, also known as kidney stone (KS), is a com- mon condition with a global concern (1). Following urinary tract infections and prostate diseases, KS is the most pre- sented urinary tract disease. Regarding epidemiology, KSs affect about 5% of females and 12% of males over their life- times (2, 3). Variations in risk factors for KSs can be observed among different population groups (4). The inci- Efficacy of Flexible ureterorenoscopy in treating multiple renal stones: A cohort study Sarwar Noori Mahmood 1, 2, Rawa Bapir 3, 4, 5, Khoshbin Faeq Mustafa 4, Ahmed Mohammed Abdalqadir 4, Shakhawan Hama Amin Said 1, Nali H. Hama 1, 3, Hiwa O. Abdullah 3, 5, Berun A. Abdalla 3, 5, Fahmi H. Kakamad 1, 3, 5 1 College of Medicine, University of Sulaimani, Sulaymaniyah, Kurdistan, Iraq; 2 Mercy Medical City, Malik Mahmood Street, Sulaymaniyah, Kurdistan, Iraq; 3 Smart Health Tower, Madam Mitterrand Street, Sulaymaniyah, Kurdistan, Iraq; 4 Department of Urology, Sulaymaniyah Teaching Hospital, Sulaymaniyah, Kurdistan, Iraq; 5 Kscien Organization for Scientific Research, Hamdi Street, Azadi Mall, Sulaymaniyah, Kurdistan, Iraq. DOI: 10.4081/aiua.2024.12617 Summary Archivio Italiano di Urologia e Andrologia 2024; 96(3):12617 S, Noori Mahmood, R, Bapir, K, Faeq Mustafa, et al. 2 a staged or auxiliary procedure to ensure an optimal stone-free rate. Eligibility criteria The inclusion criteria comprised the following: 1) Patients aged ≥ 18, presenting with multiple KSs sized between 11 and 30 mm. 2) Stones distributed anywhere within the pelvicalyceal system. 3) Conducting RIRS was based on patient preference and several characteristics, such as mor- bid obesity, congenital renal anomalies, coagulopathy, and treatment failure with PCNL or ESWL. Patients with calyceal diverticular stones, ipsilateral ureteric stones or strictures, staghorn stones, pelvic-ureteric junction obstruction, or a medullary sponge kidney were excluded. Patient examination and data collection Patients underwent preoperative assessment through non- contrast computed tomography (CT). Stone sizes were deter- mined by calculating the sum of the greatest dimensions of each stone observed on non-contrast CT scans. The col- lected data encompassed patients’ demography, family his- tory for KS, history of KS intervention, comorbidities, renal ultrasonography (U/S), non-contrast CT Kidney-Ureter- Bladder (KUB), the indication of RIRS, stone parameters (laterality, number, size), operation time, complications, and stone-free status. Complications were classified based on the Modified Clavien Classification System (MCCS) (15). Stone-free status was considered as the lack of residual stone fragments or any residual stone of any size, as deter- mined by U/S and KUB imaging. The outcomes of interest encompassed stone-free rate (SFR) and complication rates. Stones exceeding the 400-600 HU threshold were more likely classified as radiopaque, whereas those falling below were considered radiolucent, although assessment based solely on HU values may have limitations and clin- ical correlation with additional imaging modalities or stone analysis was often necessary for accurate character- ization. Intervention Under either general or spinal anesthesia and with patients positioned in lithotomy, a semi-rigid uretero- scope (8-9.5F, Karl Storz Endoscopy, Tuttlingen, Germany) was utilized for all procedures. This facilitated the passive dilation of the ureter, enabling the evaluation of the pres- ence of concurrent ureteral stones or strictures. A Zebra nitinol guidewire (0.032/0.035 inches) (Boston Scientific, USA) was threaded into the pelvicalyceal system through the ureteroscope. Following this, a 7.5 Fr flexible URS (Storz Flex-X2S, Tuttlingen, Germany), or a digital single- use ureteroscope (HU32, Shenzhen Huge Med Medical Technical Development, China), was advanced along the guidewire in a monorail manner. In patients pre-stented, a ureteral access sheath (UAS) was placed over the guidewire, followed by the advancement of the flexible URS through the UAS. Stone fragmentation was achieved using either the Holmium: YAG laser (Cyber-Ho 60 Holmium laser system, Quanta System, Milan, Italy) or the Calculase III (Storz, Tuttlingen, Germany). This involved applying 0.5-0.8 J power at a frequency of 15-30 Hz through a 200 μm fiber. To obviate the necessity for stone retrieval, a stone dusting technique was utilized, frag- menting the stones into minuscule pieces or fine powder. Following the completion of lithotripsy, a visual assess- ment of the pelvicalyceal system was conducted to detect any residual stone fragments. To prevent overlooking substantial pieces or fragments, fluoroscopy was utilized. Under direct endoscopic vision, the guidewire was care- fully inserted into the renal pelvis or collecting system. Following this, the flexible ureteroscope was gradually retracted, allowing for a thorough examination of the entire ureter to identify larger calculi, fragments, and any instances of significant ureteral damage. Subsequent to the procedure, a double-J (DJ) stent with dimensions 5-6 F and a length of 26 cm was inserted in all cases. Additionally, an indwelling Foley catheter was left in place for approximately 6-12 hours. If the postoperative course was uncomplicated, patients were discharged on the postoperative day with prescribed oral antibiotics. Follow-up The first follow-up appointment was arranged 3-4 weeks after the procedure. The KUB examination was conduct- ed, and the DJ stent was removed in the absence of any complications. In the presence of significant residual stones and substantial complications, patients underwent reintervention within 2-4 weeks. Conversely, patients without complications but with residual stones remained under observation for three months. Subsequent evalua- tions, utilizing renal U/S and KUB X-ray, took place three months after the intervention. CT scans were excluded from the diagnostic protocol to minimize expenses and reduce radiation exposure. At the three-month mark fol- lowing the intervention, the SFR was determined. This categorization included either complete stone-free status, indicating the lack of residual stone fragments, or the presence of residual stones, identified through U/S and KUB X-rays. Statistical analysis The data were organized in Microsoft Excel (2019). Subsequently, they were analyzed using the Statistical Package for the Social Sciences (SPSS) (Version 22, IBM SPSS Statistics Inc., USA). The data are presented as frequency, percentage, range, mean, and standard deviation. The chi-square test and independent samples T-test were employed to identify significant relationships between the SFR and other variables. Statistical significance was defined as p-values less than 0.05. RESULTS A total of 110 patients with multiple KSs were included, with a mean age of 45 ± 13.82 years and a mean BMI of 25 ± 3.39 kg/m2. The majority of the cases (66.4%) were male. A positive history of KS intervention was found in 26.4% of cases. Hypertension was the most common comorbidity (74.5%). Ten patients (9.1%) had a history of ischemic heart disease, and nine of them were receiving anticoagulant medications. The degree of hydronephrosis was commonly distributed between mild (39.1%) and moderate (31.8%). Renal malformation was present in 18.2% of the patients, while renal malfunction was observed in 20%. The indication for RIRS was predomi- Archivio Italiano di Urologia e Andrologia 2024; 96(3):12617 3 FURS for multiple renal stones nantly primary (80.9%). Half of the cases (50%) present- ed with two stones, 38 (34.5%) with three stones, and 17 cases (15.5%) had more than three stones. The mean stone burden was 27.5 ± 7.9 mm and the majority of them were unilateral (91.8%). Radiopaque was the prevalent radiologic characteristic of the stones (74.5%). According to Guy’s stone score (GSS), the majority of the stones were categorized as grade 2 (87.3%). Intraoperative fluo- roscopy was utilized in 52 (47.3%) patients. The mean duration of the operation and laser operating time were 54.9 ± 19.7 minutes and 31.8 ± 15.8 minutes, respective- ly. Seven cases (6.3%) experienced intraoperative compli- cations, including bleeding in four cases (3.6%) and ureteral injury in three cases (2.7%). Postoperative com- plications were urinary tract infection (5.5%) and hema- turia (1.8%), of which seven cases (6.4%) were re-admit- ted to the hospital and managed conservatively. Five cases (4.5%) needed the second stage of RIRS due to residual stones. After four weeks, stone free status was achieved in 80.9% of the cases, and this increased to 93.6% after three months (Table 1). The SFR after three months was signifi- cant with GSS; however, it did not reach a significant level with any other parameters (Tables 2 and 3). DISCUSSION Renal stones have several treatment options, each with its advantages and drawbacks. PCNL is a method known for effectively treating large KSs (16). However, it involves accessing the kidney through the renal parenchyma. Furthermore, the widely used prone position during the procedure may increase the risks associated with anes- thesia and result in a decline in oxygen saturation levels, especially in patients who are obese or elderly and already have respiratory disorders (17). Complications, including hemorrhage, hydrothorax, septicemia, bowel and major vessel injuries, and renal collecting system perforation, pose significant risks during and after this procedure. This has driven heightened interest in alternative treat- ment modalities (18, 19). Recently, there has been a growing discussion about using RIRS for multiple KSs. Several studies have investigated the feasibility and effec- tiveness of RIRS in treating the issue (20, 21). Çakıcı et al. compared the efficacy of RIRS and PCNL in treating mul- ticalyceal stones. PCNL was the preferred treatment modality unless patients had comorbidities such as anes- thesia risk, bleeding diathesis, or anatomical issues where PCNL was unsuitable (20). Alazaby et al. assessed RIRS for the treatment of multiple KSs and reached a positive conclusion regarding its efficacy. They recommended the utilization of RIRS for patients with multiple KSs, espe- cially in cases where prior treatments such as ESWL and PCNL have been unsuccessful (21). In the present study, the results indicated a favorable outcome, with the SFR reaching 93.6% at 3 months postoperatively. The mean operation time was 54.9 ± 19.7 minutes. No significant correlations were identified between the mean operation time and the SFR at both 4 weeks and 3 months postop- eratively. Ozgor et al. reported a mean operation time of 47.8 ± 22.2 minutes. Also, they reported no significant correlation between it and SFR (22). In contrast, Demirbas et al. reported a mean operative time of 62.8 ± Table 1. Baseline characteristics of the patients. Variables Frequency/Percentage Demographics Mean Age, year ± SD 45 ± 13.82 Mean BMI, kg/m2 ± SD 25 ± 3.39 Gender Male 73 (66.4%) Female 37 (33.6%) Family history for KS Yes 8 (7.3%) No 102 (92.7%) History of KS intervention Yes 29 (26.4%) No 81 (73.6%) Comorbidities Diabetes mellitus 15 (13.6%) Hypertension 82 (74.5%) Ischemic heart disease 10 (9.1%) Degree of hydronephrosis None 28 (25.5%) Mild 43 (39.1%) Moderate 35 (31.8%) Severe 4 (3.6%) Renal malformation Yes 20 (18.2%) No 90 (81.8%) Renal malfunction Yes 22 (20%) No 88 (80%) Indication of RIRS * Primary 89 (80.9%) Secondary 21 (19.1%) Number of stones Two 55 (50%) Three 38 (34.5%) More than three 17 (15.5%) Stone burden, mm (Mean ± SD) 27.5 ± 7.9 Stone laterality Right side 46 (41.8%) Left side 55 (50%) Bilateral 9 (8.2%) X-ray characteristics of stone 50 (21.9%) Radiopaque 82 (74.5%) Radiolucent 28 (25.5%) Guy’s stone score Grade 2 96 (87.3%) Grade 3 14 (12.7%) Use of fluoroscopy Yes 52 (47.3%) No 58 (52.7%) Operation time, min (Mean ± SD) 54.9 ± 19.7 Laser operating time, min (Mean ± SD) 31.8 ± 15.8 Intraoperative complication Bleeding # 4 (3.6%) Ureteral injury # 3 (2.7%) Postoperative complication Urinary tract infection # 6 (5.5%) Hematuria# 2 (1.8%) Re-admission to hospital 7 (6.4%) Re-intervention (second stage RIRS) 5 (4.5%) Stone free after 4 weeks 89 (80.9%) Stone free after 3 months 103 (93.6%) SD: Standard deviation; KS: Kidney stone; Min: minute. * A primary indication means that the patient underwent RIRS for the first time, while a secondary indication means the patient had a positive history of RIRS. # Grade II according to Modified Clavien Classification System. Archivio Italiano di Urologia e Andrologia 2024; 96(3):12617 S, Noori Mahmood, R, Bapir, K, Faeq Mustafa, et al. 4 17.57 minutes and identified a highly significant correla- tion between the procedure time and SFR (23). A mean operation time of 51.97 ± 20.18 minutes has also been reported (24). Variations in the duration of procedures among different studies may reflect the overall proficien- cy and the inherent complexities of the surgical tasks. It is crucial to recognize that these differences may also arise from varying methodologies used to estimate operative time. Notably, some practitioners begin their time assess- ment with the initiation of cystoscopy, while others com- mence the measurement at the start of URS. The SFR in the current study was similar to that Alazaby et al. reported (92.8%) (21). The similarity may be attrib- uted to the close resemblance in mean stone burden. Our reported stone burden was 27.5 mm, and Alazaby et al. reported a mean stone burden of 25.7 mm (21). In the present study, although SFR was higher with fewer stones per renal unit, the difference was not statistically signifi- cant when comparing two stones with three or more at three months post-procedure. This contrasts with Alazaby et al., who reported significant differences: 100% SFR for two stones, 77.7% for three, and 50% for four stones. In our cohort, SFR was 98.2% for two stones, 86.8% for three stones, and 94.1% for more than three stones. This discrepancy may be attributed to the larger sample size in this study and differences in the definition of SFR. The current study considered patients as stone-free when no stone fragments were detected by US and KUB, while Alazaby et al. considered SFR when fragments of 3 mm or less detected in CT-KUB (21). The current study unveiled a significant correlation between the SFR observed three months post-operation and the GSS. This may suggest that as the complexity of stones increases, the probability of achieving stone-free sta- tus diminishes within the three months following the oper- ation. This aligns with the conclusions drawn by Karsiyakali et al., who also found a significant correlation between SFR and GSS grade 3 (25). Notably, their study questioned the GSS scoring system's effectiveness in pre- dicting SFR after RIRS. This is due to the reduced utility for GSS grade 1 and grade 4 stones, making the system less effective across the entire stone complexity spectrum. As a result, their findings highlight the necessity for a nuanced approach to predict SFR post-RIRS (25). In this study, the assessment of radiopacity in stones showed no significant correlation with SFR at four weeks and three months post- operation. This aligns with Lim et al.'s findings on the rela- tionship between stone radiopacity and SFR after RIRS pro- cedures (26). Ozgor et al. similarly concluded that there was no significant correlation between these parameters (22). These outcomes emphasize the need for a nuanced consideration of factors influencing SFR beyond focusing solely on stone radiopacity in the postoperative context. With decreased instrument size, potential complications like ureteral avulsion are now extremely rare. Our study found no major complications, but 15 patients (13.6%) experienced manageable minor complications—seven intraoperative and eight postoperative. This aligns with Alazaby et al., reporting 16.6% minor complications (21). In contrast, Atis et al. documented 3.4% minor complica- tions in their RIRS group; this variance may be due to vary- ing sample sizes, and notably, our cohort included intra- operative complications (27). This research is subject to several limitations, including the study's small sample size, which limits its generalizability. The definition of stone burden varies, introducing potential inconsistencies. Additionally, the absence of a comparison with alternative stone treatment methods hinders a comprehensive assess- ment. The study's short follow-up duration restricts the evaluation of long-term outcomes. To avoid citing non- peer-reviewed data, the authors ensured the credibility of the referenced studies (28). Table 2. Correlation of SFR with RIRS indication, stone characteristics, stent placement, and ureteric access sheath. Variable No. Stone free after 4 weeks P-value * Stone free after 3 months P-value * IIndication of RIRS Primary 89 72 (80.9%) 0.63 84 (94.4%) 0.40 Secondary 21 17 (81%) 19 (90.5%) Number of stones 2 55 48 (87.3%) 0.14 54 (98.2%) 0.08 3 38 27 (71.1%) 33 (86.8%) > 3 17 14 (82.4%) 16 (94.1%) Pre-operative stent placement Yes 23 18 (78.3%) 0.46 21 (91.3%) 0.45 No 87 71 (81.6%) 82 (94.3%) X-ray characteristics Radio-opaque 82 67 (81.7%) 0.45 77 (93.9%) 0.57 Radiolucent 28 22 (78.6%) 26 (92.9%) Use of ureteric access sheath Yes 80 66 (82.5%) 0.33 75 (93.8%) 0.61 No 30 23 (76.7%) 28 (93.3%) Guy’s Stone Score G2 96 77 (80.2%) 0.068 90 (93.8%) < 0.001 G3 14 13 (92.9%) 14 (100%) * Chi-square test. SFR: Stone-free rate; RIRS: Retrograde intrarenal surgery. Table 3. Correlation of stone burden and operation time with SFR. Variable SFR after 4 weeks P-value ** SFR after 3 months P-value ** Yes (89) No (21) Yes (103) No (7) Mean stone burden (mm) 27.10 ± 8.44 29.09 ± 4.97 0.15 27.40 ± 8.0 29.30 ± 4.85 0.26 Mean operation time (min) 54.40 ± 20.36 57.14 ± 16.77 0.39 54.94 ± 19.70 55 ± 21 0.82 ** Independent t-test. Archivio Italiano di Urologia e Andrologia 2024; 96(3):12617 5 FURS for multiple renal stones In conclusion, RIRS with flexible URS may be an effective and potentially safe procedure for treating multiple KSs. It may yield an excellent SFR with an acceptable compli- cation rate. REFERENCES 1. Said SH, Al Kadum Hassan MA, Ali RH, et al. Percutaneous nephrolithotomy; alarming variables for postoperative bleeding. Arab J Urol. 2017; 15:24-29. 2. Bhatti KH, Bapir R, Bhatti WS, et al. Efficacy of sexual interco- surse in the spontaneous passage of distal or intramural ureteral stones: a randomsized controlled trial. Ann Med Surg (Lond). 2023; 85:5972-5976. 3. Guan F, Han W, Ni T, et al. 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Abdullah, MD Berun Abdalla, MD berun.anwer95@gmail.com Smart Health Tower, Madam Mitterrand Street, Sulaymaniyah, Kurdistan, Iraq Khoshbin Faeq Mustafa, MD Ahmed Mohammed Abdalqadir, MD Department of Urology, Sulaymaniyah Teaching Hospital, Sulaymaniyah, Kurdistan, Iraq Fahmi Hussein Kakamad, MD (Corresponding Author) fahmi.hussein@univsul.edu.iq Doctors City, Building 11, Apartment 50, Sulaimani, Iraq Conflict of interest: The authors declare no potential conflict of interest.