Abstract Aims Small common bile duct stones are known to occasionally clear spontaneously. This study aimed to prospectively assess the role of biliary stent placement in promoting the spontaneous clearance of small common bile duct stones. Methods and Results We analyzed patients presenting with common bile duct stones of ≤5 mm diameter between June 2020 and May 2022. The exclusion criteria included asymptomatic patients, biliary pancreatitis, altered gastrointestinal anatomy, bile duct strictures (malignant or benign), and a history of EST. The biliary stents were inserted without stone removal. Stone clearance was assessed using endoscopic ultrasonography or endoscopic retrograde cholangiopancreatography after 3 months. Our primary endpoint was the clearance rate of common bile duct stones over 6 months, targeting a lower limit for the 95% confidence interval (CI) exceeding 25%. Of the 32 enrolled patients, 18 (56.3%; 95% CI: 37.7–73.6%) exhibited stone clearance. Early complications occurred in 11 patients (34.4%), totaling 12 incidents: acute cholecystitis in four, acute pancreatitis in three, biliary pain in three, and cholangitis in two patients. No severe complications occurred. Six (18.8%) patients experienced asymptomatic stent migration. Following stone clearance, four (12.5%) patients experienced stone recurrence, with an average duration of 256 ± 164 days. Conclusion Biliary stenting appeared to effectively promote the clearance of small common bile duct stones in approximately half of the patients. However, the potential complications and risks of stone recurrence warrant close monitoring. This trial was registered in the Japan Registry of Clinical Trials (jRCT1042200020).
