Stesura Seveso 439Archivio Italiano di Urologia e Andrologia 2022; 94, 4 ORIGINAL PAPER No conflict of interest declared. stone composition, size, and location, as well as the mech- anism and parameters of the shockwave generator (1). Several studies have proved that stone attenuation values – measured in Hounsfield Units (HU) on computed tomogra- phy (CT) – can predict the outcome of SWL. Although the threshold values differ in various studies it has generally been accepted that higher CT attenuation values have poor outcomes in terms of success rates (2-5). However, most of these studies address only the role of CT attenuation values from the success rate standpoint and there is a paucity of literature investigating the association between preopera- tive stone characteristics and the need for postoperative ancillary procedures. We believe that the challenge is not only to fragment the stone, but also to reduce the risk of subsequent ancillary treatments. Ancillary treatments such as ureteroscopy (URS) and hospital readmission for pain or fever are frequently encountered after SWL. These ancillary treatments have put an undue burden on urological treat- ment waiting lists. For small ureteral or renal calculi, SWL has a comparable efficacy when compared with retrograde intra-renal sur- gery (RIRS) (6). According to the latest guidelines, SWL should be considered as the first treatment option in patients with renal stones less than 20 mm and without unfavorable factors for SWL success (1). However, the predictors for ancillary procedures after SWL are still under investigated and eagerly awaited. Therefore, the aim of the present study was to investigate the predictors for the ancillary treatments after (SWL) for renal and upper ureteral stones. MATERIALS AND METHODS From January 2014 to January 2017, patients undergoing SWL using an electromagnetic lithotripter machine (Compact Delta; Dornier MedTech GmbH, Wessling, Germany) for renal and upper ureteral stones ≤ 20 mm were retrospectively reviewed. All patients included in the analysis underwent CT urography prior to SWL. The cohort was subdivided into three groups according to stone attenuation values (HU). Group I; HU < 500, group II; HU 500-1000 and group III; HU ≥ 1000. The param- Objective: To quantify the predictors for the ancillary treatments after extracorporeal shock wave lithotripsy (SWL) for renal and upper ureteral stones. Materials and methods: From January 2014 to January 2017, patients undergoing SWL using an electromagnetic lithotripter machine (Compact Delta; Dornier MedTech GmbH, Wessling, Germany) for renal and upper ureteral stones ≤ 20 mm were retrospectively reviewed. All patients underwent CT urography prior to SWL. The cohort was subdivided into three groups according to stone attenuation values in Hounsfield Units (HU). Group I; HU < 500 (n = 20), group II; HU 500-1000 (n = 51) and group III; HU ≥ 1000 (n = 180). The parameters included for multivariate analysis were stone size, location, multiplicity, stone attenuation value, number of shocks and stone clearance rate by 3 months. The ancillary treatments were ureteroscopy (URS), ureteral stenting and hospital readmission for pain or fever. Results: A total of 251 patients were included in the study. The overall SWL success rate was 92.4%. Mean stone size was 10.9 ± 2.1, 11.6 ± 3 and 11.4 ± 3.6 mm and mean stone attenua- tion values were 364 ± 125, 811 ± 154 and 1285 ± 171 HU for groups I, II and III respectively. The stone clearance rates by 3 months were 96%, 92% and 88.4% for groups I, II and III respec- tively. On subgroup analysis, group III required ancillary treat- ments in 70% of patients whereas group I, II, did not require any ancillary treatments. On multivariate analysis, stone multiplicity, stone location (lower calyceal stones) and HU were independent significant predictors for the need for ancillary treatments after SWL (p values < 0.05). Conclusions: Patients with stone attenuation value (HU) > 1000, multiple stones and/or lower calyceal stones have higher risk to necessitate ancillary treatments after SWL. These patients would likely benefit from upfront endoscopic lithotripsy for treating symptomatic renal or upper ureteral stones. Key WORDS: SWL; Urolithiasis; Fragmentation; Ancillary treatment; Lower calyceal stone. Submitted 19 November 2022; Accepted 5 December 2022 INTRODUCTION The outcome of extracorporeal shockwave lithotripsy (SWL) relies on several factors, including stone factors such as Can we predict the ancillary treatments after extracorporeal shockwave lithotripsy for renal and upper ureteral stones? Ahmed Ibrahim 1, Adel Elatreisy 2, Abdulghani Khogeer 3, Abdulsalam Ahmadi 4, Shashikant Mishra 4, Mahmoud Faisal 2, Ravindra Sabnis 4, Mélanie Aubé-Peterkin 1, Serge Carrier 1, Arvind Ganpule 4, Mahesh Desai 4 1 Department of Surgery, Division of Urology, McGill University Health Center, Montreal QC, Canada; 2 Urology Department, Al-Azhar University, Cairo, Egypt; 3 Department of Surgery, Faculty of Medicine, Rabigh, King Abdulaziz University, Jeddah, Saudi Arabia; 4 Muljhibhai Patel Urological Hospital, Nadiad, India. * Co-First Author. DOI: 10.4081/aiua.2022.4.439 Summary Archivio Italiano di Urologia e Andrologia 2022; 94, 4 A. Ibrahim, A. Elatreisy, A. Khogeer, et al. 440 eters included in the multivariate analysis were stone size, location, multiplicity, stone attenuation value, number of shocks and stone clearance rate by 3 months. Ureteroscopy (URS), ureteral stenting and hospital read- mission for pain or fever were considered post-SWL ancillary procedures. For each stone, the mean attenua- tion value was calculated from a small, non-overlapping region of interest. The SWL procedures were all performed as previously described (3). The treatments were performed under con- scious sedation using intravenous fentanyl as the primary anesthetic agent. The stones were located under fluoro- scopic and/or ultrasonographic guidance, and the shock impulses were given at a frequency of 60 shocks per min- utes in all patients (1 Hz). Shock impulse energy was started at level 1 (10 kv) and ramped up to 6 level (16 kv). The total number of shocks did not exceed 3000. Plain X-ray kidney-ureter-bladder (KUB) and ultrasound were performed 6 weeks post SWL. Success rate was defined as inability to detect stone on ultrasound and KUB or a residual fragment measuring less than 4 mm. Review of literature A PubMed-MEDLINE search was conducted for SWL contemporary literature and relevant data regarding SWL auxiliary procedures and predictors of failure. Several articles based on the same patient cohort and success rate measures were included. Statistical analysis Statistical analyses were performed using SPSS (SPSS Inc., Chicago, IL, USA) version 22. Comparison of quantitative variables was done using the paired t test (if normally dis- tributed) or the Wilcoxon signed rank test (if not nor- mally distributed) or Fisher’s exact test for categorical variable. A multivariate logistic regression analysis was used to assess predictors of postoperative ancillary treat- ments. Two-tailed p-values of less than 0.05 were set for statistical significance. RESULTS A total of 251 patients were included in this study, including 20 patients in group I, 51 patients in group 2 and 180 patients in group 3. The overall SWL success rate at 3 months was 92.4% including 14 patients (5.5%) who developed post SWL steinstrasse. The mean stone size was 10.9 ± 2.1, 11.6 ± 3 and 11.4 ± 3.6 mm and the mean stone attenuation values were 364 ± 125, 811 ± 154 and 1285 ± 171 HU for groups I, II and III respec- tively. Stone clearance rates were 96%, 92%, 88.4% for groups I, II and III respectively. SWL failure was encoun- tered in 26 patients (10.4%), 24 patients of them (6.8%) were stone-free after second session of SWL and 2 patients (0.8%) necessitated URS. The three groups were comparable in terms of body mass index, stone size and stone location (Table 1). On subgroup analysis, group III patients required URS and ureteral stenting in 10 cases (5.6%), and hospital readmission for persistent renal colic in 4 cases (2.2%) whereas no patients in groups I and II required ancillary treatments. Univariate analysis revealed that there was a significant correlation between age, stone location, stone multiplici- ty, HU and the need for ancillary procedures (p < 0.05) whereas no significant correlation could be detected for stone size, and gender (Table 2). On multivariate analy- sis, it was found that stone multiplicity, stone location and HU were independent significant predictors for the treatments after SWL (p values < 0.05) (Table 2). Table 3 summarizes SWL contemporary series tracking the required auxiliary procedures after SWL and predic- tors of SWL failure (7-20). DISCUSSION According to the latest guidelines, SWL remains the proce- dure of choice for most upper urinary tract stones ≤ 20 mm in size because of its minimally invasive nature, shorter operative time, established success rates, and minimal complications with long-term safety (1). However, SWL monotherapy is not successful in 9.4% to 26.3% of renal and upper ureteric stones (6, 21). Several studies have shown that SWL efficacy is significantly lower for stones with higher attenuation values (5-8). Nevertheless, there is Table 1. Patients and stone demographic data. Parameter Value Mean age ± SD (years) 37.79 ± 17.7 Gender Male 181 Female 70 Mean BMI (Kg/M2) 23.97 ± 3.8 Stone side, n (%) Right 125 Left 126 Mean stone size ± SD (mm) 11.46 ± 2.74 Multiple stones, n (%) 19 (7.57%) Stone location, n (%) Upper calyx 21 (8.37%) Middle calyx 44 (17.53%) Lower calyx 50 (19.92%) Renal pelvis 82 (32.67%) Upper ureter 54 (21.51%) Associated hydronephrosis, n (%) Mild 51 (20.32%) Moderate 25 (9.96%) Mean Stone attenuation value (HU) 1115 ± 329.79 Overall SWL success rate 92.4% SWL onset, n (%) Primary treatment 243 (96.8%) Residual stone post PCNL and RIRS 16 (6.4%) Table 2. Predictors for ancillary treatments using univariable and multivariate regression analysis. Variable Univariable Multivariable OR 95%CI p OR 95%CI p Age, years 1.04 (1.01, 1.07) 0.027 0.97 (0.89-1.71) 0.09 Stone size (mm) 0.81 (0.78-1.11) 0.082 Stone location 1.18 (0.88-1.01) 0.01 1.1 (0.99–1.78) 0.02 Stone multiplicity 2.81(1.26-3.54) < 0.001 1.45 (1.16–2.11) 0.01 Number of shocks per session 0.91 (0.54–1.02) 0.306 HU (< 1000 vs. ≥ 1000) 2.75 (1.40-4.99) 0.001 3.01 (1.61-6.71) 0.01 Gender, Male/Female 0.81 (0.51–1.00) 0.351 OR = Odds ratio; CI = Confidence interval; HU = Hounsfield unit. 441Archivio Italiano di Urologia e Andrologia 2022; 94, 4 Ancillary treatments after SWL a paucity of literature investigating the association between preoperative stone characteristics and the need of postop- erative ancillary procedures. Therefore, the aim of the pres- ent study was to investigate the predictors for the ancillary treatments after (SWL) for renal and upper ureteral stones. It was found that overall SWL success rate at 3 months was 92.4%. After 3 months follow-up, the stone-free rates were 96%, 92%, and 88.4% for groups I, II, and III respectively. On subgroup analysis, group III (HU > 1000) required URS and ureteral stenting in 5.6% of patients, and hospital readmission for persistent renal colic in 2.2% whereas groups I and II did not require any ancillary treatments. These results are consistent with current medical literature, indicating that SWL is associ- ated with significantly higher retreatment rates compared with RIRS and PCNL (21). On multivariate analysis, it was found that stone multiplicity, stone location and HU > 1000 were independent significant predictors for the treatments after SWL (p values < 0.05; Table 2). Interestingly, when we analyzed stone location cases, we found that most of the lower calyceal stone were associ- ated with SWL failure and required ancillary treatments. It was reported that several factors such as obesity, stone density, stone composition and unfavorable lower pole anatomy would also affect stone clearance rates (22). These results may change our clinical practice in the fol- lowing manner; for those patients with multiple stones, a 1-2 cm lower calcyeal stone or stone attenuation value > 1000 HU and who are anxious about the increased com- plication rates of RIRS and PCNL and do not mind retreat- ment or multiple procedures, SWL could be considered an acceptable first management option. Favorable lower pole anatomy [infundibular-pelvic angle (> 30°), short calyx (< 10 mm), and wide infundibulum (> 5 mm)] should also be considered in the treatment algorithm (22). Most patients, who fail primary SWL treatment, are best suited to be treated with endoscopic treatments (RIRS or PCNL) due to its high stone-free rate, significantly lower operative and fluoroscopy time. However, patients with challenging lower pole calyceal anatomy, PCNL would be the first option. Our study had some limitations including, first the retro- spective nature resulting in some missing data such as stone to skin distance, infundibulo-pelvic angle. However, these variables are sufficiently reported in med- ical literature. Secondly, there exists a selection bias which explains the high heterogeneity between groups. Finally, the interpretation of our findings may be affected by these confounders. Nevertheless, this is one of the rare studies investigating the predictors for the ancillary treat- ments after SWL. CONCLUSIONS Our study suggests that patients with stone attenuation value (HU) > 1000, multiple stones and/or lower calyceal stones have higher risk to necessitate ancillary treatments after SWL. Those patients could be offered an endoscop- Table 3. Contemporary published SWL series. Series Study design N Ancillary treatment Success rate Predictors of failure Garrido-abad et al. (7) Retrospective 270 N/A 68.8% - Stone size > 9.3 mm - Stone volume > 237 - SAV > 951, SSD 133 mm - BMI > 26.9 Nakasato et al. (8) Retrospective 260 N/A 76.5% - HU > 815 - Stone location Massoud et al. (9) Prospective 305 - Stienstrusse in 3.6% - BMI > 30 - Conservative in 2.6% - Lower calyceal stone - URS in 10.8% 83% - SAV > 956.5 Abdelaziz et al. (10) Retrospective 89 N/A 68.5% - HU > 800 - SSD > 11.2 ± 2.6 cm Quzaid et al. (11) Prospective 50 N/A 52% - HU > 970 Park et al. (12) Retrospective 43 N/A 69.7% - SSD > 92.03 ± 14.51 mm Olive et al. (13) Retrospective 98 - Cystoscopy + ureteric stents in 40.6% 56.3% - Obesity - BMI > 35 Bandi et al. (14) Retrospective 94 N/A 62% - Stone volume > 500 microL. Talas et al. (15) Retrospective 198 N/A 61% - In lower calyceal stones - IP angle and infundibular width Al-ansari et al. (16) Retrospective 427 - Post-ESWL 78% - Stone size, location and number - Auxiliary procedures were required in 8.4% - Radiological renal features and congenital renal anomalies. Ghoneim et al. (17) Retrospective 205 N/A 68.8% - IP Angle more than 70 degrees - Infundibular length of > 50 mm Wang et al. (18) Prospective 89 N/A 52.5% - Stone burden > 700 mm3 - Stone density of > 900 HU Abdel-khalek et al. (19) Retrospective 2954 - Static steinstrassae in 4.9%. 86.7% - Patient age, stone size, location and number - Auxiliary - Radiological renal features and congenital renal anomalies - Procedures in 4% Sumino et al. (20) Retrospective 63 N/A 54% - Higher infundibular Length-to-diameter ratio - Diameter and number of minor calices Archivio Italiano di Urologia e Andrologia 2022; 94, 4 A. Ibrahim, A. Elatreisy, A. Khogeer, et al. 442 ic lithotripsy as a first line therapy for treating sympto- matic renal or upper ureteral stones. Future prospective studies are definitely warranted. REFERENCES 1. Türk C, Knoll T, Petrik A, et al. EAU guidelines on urolithiasis. Eur Urol. 2014; 258-89. 2. Jeong US, Lee S, Kang J, Han DH, et al. Factors affecting the out- come of extracorporeal shock wave lithotripsy for unilateral urinary stones in children: a 17-year single-institute experience. Korean J Urol. 2013; 54:460-466. 3. Hevia M, García Á, Ancizu FJ, et al. Predicting the effectiveness of extracorporeal shock wave lithotripsy on urinary stones, risk groups for accurate retreatment. Actas Urol Esp. 2017; 41:451-457. 4. El-Nahas AR, EI-Assmy AM, Madbouly K, et al. Predictors of clin- ical significance of residual fragments after extracorporeal shock- wave lithotripsy for renal stones. J Endourol. 2006; 20:870-4. 5. Weld KJ, Montiglio C, Morris MS, et al. Shock wave lithotripsy success for renal stones based on patient and stone computed tomog- raphy characteristics. Urology. 2007; 70:1043-1046. 6. Garrido-Abad P, Rodríguez-Cabello MÁ, Platas-Sancho A. Analysis of success predictive factors in the treatment of urinary lithi- asis by extracorporeal shock wave lithotripsy. patient optimization: ESWL score. Arch Esp Urol. 2017; 70:715-724. 7. Nakasato T, Morita J, Ogawa Y. Evaluation of Hounsfield Units as a predictive factor for the outcome of extracorporeal shock wave lithotripsy and stone composition. Urolithiasis. 2015; 43:69-75. 8. Massoud AM, Abdelbary AM, Al-Dessoukey AA, et al. The success of extracorporeal shock-wave lithotripsy based on the stone-attenua- tion value from non-contrast computed tomography. Arab J Urol. 2014; 12:155-61. 9. Abdelaziz H, Elabiad Y, Aderrouj I, et al. The usefulness of stone density and patient stoutness in predicting extracorporeal shock wave efficiency: Results in a North African ethnic group. Can Urol Assoc J. 2014; 8: E567-9. 10. Ouzaid I, Al-qahtani S, Dominique S, et al. A 970 Hounsfield units (HU) threshold of kidney stone density on non-contrast com- puted tomography (NCCT) improves patients' selection for extracor- poreal shockwave lithotripsy (ESWL): evidence from a prospective study. BJU Int. 2012; 110:E438-42. 11. Byung-Hun Park, Hoon Choi, Jin-Bum Kim, and Young-Seop Chang. Analyzing the Effect of Distance from Skin to Stone by Computed Tomography Scan on the Extracorporeal Shock Wave Lithotripsy Stone- Free Rate of Renal Stones. Korean J Urol. 2012; 53:40-43. 12. Olivi B1, Védrine N, Costilles T, et al. Extra corporeal shock wave lithotripsy in patients with body mass index over 35 Kg/m2. Prog Urol. 2011; 21:254-9. 13. Bandi G, Meiners RJ, Pickhardt PJ, Nakada SY. Stone measure- ment by volumetric three-dimensional computed tomography for pre- dicting the outcome after extracorporeal shock wave lithotripsy. BJU Int. 2009; 103:524-8 14. Talas H, Kilic O, Tangal S, Safak M. Does lower-pole caliceal anatomy predict stone clearance after shock wave lithotripsy for pri- mary lower-pole nephrolithiasis?. Urol Int. 2007; 79:129-32. 15. Al-Ansari A1, As-Sadiq K, Al-Said S, et al. Prognostic factors of success of extracorporeal shock wave lithotripsy (ESWL) in the treat- ment of renal stones. Int Urol Nephrol. 2006; 38:63-7. 16. Ghoneim IA, Ziada AM, Elkatib SE. Predictive factors of lower calyceal stone clearance after Extracorporeal Shockwave Lithotripsy (ESWL): a focus on the infundibulopelvic anatomy. Eur Urol. 2005; 48:296-302. 17. Wang LJ1, Wong YC, Chuang CK. Predictions of outcomes of renal stones after extracorporeal shock wave lithotripsy from stone characteristics determined by unenhanced helical computed tomog- raphy: a multivariate analysis. Eur Radiol. 2005; 15:2238-43. 18. Abdel-Khalek M, Sheir KZ, Mokhtar AA, et al. Prediction of suc- cess rate after extracorporeal shock-wave lithotripsy of renal stones--a multivariate analysis model. Scand J Urol Nephrol. 2004; 38:161-7. 19. Sumino Y, Mimata H, Tasaki Y, et al. Predictors of lower pole renal stone clearance after extracorporeal shock wave lithotripsy. J Urol. 2002; 168:1344-7. 20. Zhang W, Zhou T, Wu T, et al. Retrograde Intrarenal Surgery versus Percutaneous Nephrolithotomy versus Extracorporeal Shockwave Lithotripsy for Treatment of Lower Pole Renal Stones: A Meta-Analysis and Systematic Review. J Endourol. 2015; 29:745-59 21. Junbo L, Yugen L, Guo J, et al. Retrograde Intrarenal Surgery vs. Percutaneous Nephrolithotomy vs. Extracorporeal Shock Wave Lithotripsy for Lower Pole Renal Stones 10-20 mm: A Meta-analysis and Systematic Review. Urol J. 2019; 16:97-106. 22. Bozzini G, Verze P, Arcaniolo D, et al. A prospective randomized comparison among SWL, PCNL and RIRS for lower calyceal stones less than 2 cm: a multicenter experience: A better understanding on the treatment options for lower pole stones. World J Urol. 2017; 35:1967-75. Correspondence Ahmed Ibrahim, MD ahmed.eldemerdash@muhc.mcgill.ca Adel Elatreisy, MD (Corresponding Author) dr_adelelatreisy@yahoo.com Al-Azhar University, Faculty of Medicine Cairo, Egypt Abdulghani Khogeer, MD dr-abdulghani@hotmail.com Abdulsalam Ahmadi, MD abdulsalamahmadi@hotmail.com Shashikant Mishra, MD mishra@mpuh.org Mahmoud Faisal, MD drfaysl2012e@yahoo.com Ravindra Sabnis, MD rbsabnis@gmail.com Mélanie Aubé-Peterkin, MD melanie.aube-peterkin@mcgill.ca Serge Carrier, MD serge.carrier@mcgill.ca Arvind Ganpule, MD doctorarvind1@gmail.com Mahesh Desai, MD mrdesai@mpuh.org