Assessment of pancreatic ductal stone density on non-contrast computed tomography for predicting the outcome of extracorporeal shock wave lithotripsy

Abstract

Background and Aims: The utility of stone density at non-contrast computed tomography (NCCT) for predicting the effectiveness of extracorporeal shock wave lithotripsy (ESWL) in chronic calcific pancreatitis (CCP) is relatively unexplored. Methods: This is a prospective observational study of patients with CCP. Hounsfield units (HU) was determined for the largest pancreatic ductal stone during pretreatment NCCT. All patients underwent ESWL till the largest stone was fragmented to < 3 mm, followed by ERCP for stone extraction. The predicting factors following ESWL for successful stone extraction were studied, and the ROC curve determined the HU optimal cut-point. Results: Eighty-two patients with a median (IQR) age of 36(29-55) years; majority male 45 (54.9%), were included. Idiopathic CCP was noted in 78(95.1%) patients. The median stone density (SD) was 1095(860.7-1260.7) HU, and the number of ESWL sessions was 2(2-3). Complete stone removal at index ERCP was achieved in 55(67.1%) patients. Those with partial clearance (n=27) needed a repeat ERCP, which was successful in 26(96.3%); 1(3.7%) patient underwent surgery. There was a significant, positive correlation between number of ESWL sessions and SD (r=0.797; p<.001). On bivariate analysis, SD and the number of ESWL sessions revealed a significant association with complete ductal clearance. The optimal cut-point for complete stone removal by the ROC curve was 1106.5 HU (Youden index 0.726), with a sensitivity of 93% and a specificity of 80%. Conclusions: The SD is a significant predictor of ESWL success followed by ductal clearance at ERCP, and <1106.5 HU are good candidates for ESWL therapy.