Abstract: Objective The aim of this study was to investigate diagnostic performance of endoscopic ultrasonography (EUS) in comparison with abdominal ultrasonography (US), computed tomography (CT) and magnetic resonance cholangiopancreatography (MRCP) in detecting sludge-like stones in the common bile duct. Methods 67 patients with sludge-like stones and 70 patients with formed stones were encountered in our hospital between August 2022 and June 2025, and all underwent EUS, US, CT and MRCP, and endoscopic retrograde cholangiopancreatography (ERCP) or surgical removal of stones. Results Of 67 patients with sludge-like common bile duct stones proven by EUS, stones presented as diffuse punctate hyperechoic spots in 59 cases (88.1%), blurred bile duct walls or focal thickened in 52 cases (77.6%), stratified deposition in 46 cases (68.7%), faint tapering shadow in 41 cases (61.2%) and flocculent floating echoes in 38 cases (56.7%); the AUCs were 0.92, 0.95, 0.97 and 0.99 by US, CT, MRCP and EUS in detecting formed stones, while they were 0.73, 0.78, 0.83 and 0.98 in detecting sludge-like stones,suggesting EUS detection much superior to conventional imaging; of the 67 patients with sludge-like stones proven by EUS, misdiagnosis by US, CT, MRCP occurred in 49 cases (73.1%), and of which, either US, CT or MRCP didn’t find it in 5 cases (7.5%); reasons of missed diagnosis included diameter of stone less than 3 mm, scattered deposition or lack of typical echo, etc. Conclusion EUS holds significant diagnostic value for sludge-like stones in the common bile ducts, particularly when conventional imaging results are negative or atypical. Future studies should further validate the specific signs of sludge-like stones on EUS and explore its role in monitoring and treatment strategy selection, which might provide a more robust evidence for the precise diagnosis and management of biliary diseases.

Key words: Common bile duct stones, Sludge-like stones, Endoscopic ultrasonography, Endoscopic retrograde cholangiopancreatography, Diagnosis