Predictors of Successful Stone Fragmentation and Extraction Using Electrohydraulic Lithotripsy: A Multicentric Study

Introduction: In most cases (∼ 90%), biliary stones are successfully removed by ERCP, while extra-corporeal shock wave lithotripsy (ESWL) is considered the first line treatment for pancreatic duct stones. If these techniques fail, electrohydraulic lithotripsy (EHL) or other techniques such as laser or mechanical lithotripsy can be attempted. No single strategy is best for all patients, and many factors may come into play when deciding which of these to proceed with. We would like to explore which of these factors might help predict successful stone fragmentation and subsequent extraction using EHL. Methods: A multicentric retrospective chart review study was conducted among 4 academic centers. Three hundred and seventy seven ERCP procedures with EHL were identified. Continuous variables were described as mean ± Standard deviation (SD), categorical variables were described as proportions or percentages. Univariable logistic regression was done to assess for association of different covariates with the outcomes of successful stone fragmentation (SF) and complete final extraction (FE), and multivariable logistic regression models were then constructed for each outcome. Factors such as gender and smoking status, number of stones, stone impaction, stone size, altered anatomy, and quality of image during cholangioscopy were evaluated. Results: Mean age was 61.9 ± 16.6. 57% were female. On univariable analysis, increasing stone size and number, impaction and sub-optimal contrast and scope image quality were significantly associated with decreased SF. Similarly sub-optimal contrast and scope image quality, increasing stone size and number, as well as impaction were significantly associated with decreased FE, in addition to smoking. On multivariate analysis, all factors that were significant on univariable analysis remained independently associated with SF (Table 1). In contrast, only increasing stone size and smoking status remained independently associated with FE. All other variables were not significantly associated with SF or FE. Conclusion: Stone size and number, impaction and sub-optimal image quality were negatively associated with successful EHL fragmentation, while stone size and being a smoker were associated with a lower rate of complete final extraction. Larger sample sizes may be needed to create a complete model for accurate prediction of successful EHL. Table 1. - Clinically relevant factors associated with stone fragmentation and final extraction Variables Stone fragmentation Final extraction Univariable analysis Multivariable analysis Univariable analysis Multivariable analysis OR (95% CI) P-value OR (95% CI) P-value OR (95% CI) P-value OR (95% CI) P-value Gender (reference female) 1.44(0.92-2.25) 0.49 N/A N/A 1.16 (0.76-1.75) 0.49 N/A N/A Smoking status (reference smoker) 1.52 (0.95-2.43) 0.08 N/A N/A 1.74 (1.13-2.67) 0.012 2.37 (1.18-4.76) 0.015 Number of stones: 2 or more (reference is 1 stone) 0.46(0.17-1.22) 0.19 N/A N/A 0.39 (0.16-0.92) 0.033 0.66 (0.06-6.98) 0.73 Largest stone size (in mm) 0.88 (0.84-0.92) < 0.001 0.86 (0.80-0.91) < 0.001 0.89 (0.85-0.93) < 0.001 0.83 (0.83-0.93) < 0.001 Intra-hepatic stone (reference is no) 1.21 (0.66-2.21) 0.54 N/A N/A 0.63 (0.37-1.09) 0.10 N/A N/A Impacted stone (reference is no) 0.33 (0.19-0.55) < 0.001 0.37 (0.16-0.87) 0.022 0.51 (0.30-0.85) 0.010 0.96 90.41-2.26) 0.93 Cholangioscope image quality: Good (reference is excellent) 0.43 (0.23-081) 0.009 1.38(0.51-3.73) 0.53 0.46 (0.25-0.86) 0.015 0.52 (0.20-1.38) 0.19 Cholangioscope image quality :Poor (reference is excellent) 0.16 (0.29-0.90) 0.04 0.06 (0.005-0.67) 0.022 0.12 (0.01-1.03) 0.05 0.14 (0.01-1.46) 0.1 Contrast image quality: Good (Reference is excellent) 0.33 (0.20-.56) < 0.001 0.28 (0.12-0.68) 0.005 0.52 (0.32-0.85) 0.009 0.78 (0.34-1.79) 0.56 Contrast image quality: poor (reference is excellent) 0.59 (0.11-3.33) 0.55 0.12 (0.02-0.88) 0.037 1.24 (0.22-6.92) 0.81 1.32 (0.13-13.04) 0.81 Altered anatomy (reference is no) 0.71 (0.36-1.44) 0.35 N/A N/A 0.556 (0.28-1.1) 0.09 N/A N/A Prior cholecystectomy (reference is no) 0.93 (0.059-1.45) 0.74 N/A N/A 0.66 (0.44-1.00) 0.05 N/A N/A Only variables that were significantly associated (P-value<0.05) with each outcome on univariable logistic regression are included in the corresponding multivariable logistic regression. OR: Odds ratio, N/A: Not applicable.