ObjectiveTo study the clinical value of endoscopic ultrasonography (EUS) before endoscopic retrograde cholangiopancreatography (ERCP) in patients with non-deterministic choledocholithiasis. MethodsData of 132 patients with unconfirmed common bile duct calculi diagnosed in Tianjin Nankai Hospital from January 2017 to December 2019， whose clinical manifestations were not consistent with magnetic resonance cholangiopancreatography (MRCP) results, were retrospectively analyzed. Patients were divided into two groups: group A showed calculi under MRCP with no suspicious clinical manifestations, while group B showed no calculi under MRCP with suspected clinical manifestations. All patients underwent EUS. Necessity of ERCP was determined according to EUS results, and the diagnostic accuracy of EUS was analyzed compared with ERCP results and follow-up results as the gold standard. ResultsOf the 132 patients, 87 were confirmed as choledocholithiasis, and 45 had no common bile duct calculi by the golden standard. Forty-four (33.3%) cases were negative in EUS and were confirmed free of calculi by follow-up. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of EUS for choledocholithiasis were 95.40% (83/87), 97.78% (44/45), 96.21% (127/132), 98.81% (83/84) and 91.67% (44/48), respectively.The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of MRCP for choledocholithiasis were 66.67% (58/87), 82.22% (37/45), 71.97% (95/132), 87.88% (58/66) and 56.06% (37/66), respectively. There were significant differences in the sensitivity, accuracy, positive predictive value or negative predictive value between EUS and ERCP (all P<0.05). There was significant consistency between the EUS results and the final diagnosis (Kappa=0.917, P<0.001), and good consistency between MRCP results and the final diagnosis (Kappa=0.439, P<0.001). The detection rate of false positive MRCP in group A was higher than that of false negative MRCP in group B [8/8 VS 89.66% (26/29), P<0.001] under EUS. ConclusionEUS is superior to MRCP in the diagnosis of uncertain choledocholithiasis, and EUS prior to ERCP can reduce unnecessary ERCP operations and avoid missing stones.