Short-term prophylactic biliary stenting after complete common bile duct stone removal to prevent post-ERCP cholangitis in Japan (STEP-ERCP study): study protocol for a confirmatory multicentre randomised controlled trial.

INTRODUCTION: Endoscopic retrograde cholangiopancreatography (ERCP) is the standard treatment for common bile duct stones. Although complete stone removal can be achieved in most cases, post-ERCP cholangitis still occurs in a subset of patients, even in the absence of preprocedural cholangitis. Temporary prophylactic biliary stenting after complete stone extraction may reduce post-ERCP cholangitis by preventing transient biliary obstruction caused by papillary oedema, impaired bile drainage or residual biliary sludge. However, evidence supporting this strategy is currently limited to retrospective studies. The STEP-ERCP study is designed to test the hypothesis that short-term prophylactic biliary stenting after complete removal of common bile duct stones reduces the incidence of post-ERCP cholangitis compared with no biliary stenting.

METHODS AND ANALYSIS: The STEP-ERCP study is a multicentre, prospective, open-label, randomised controlled superiority trial. Adult patients undergoing ERCP for common bile duct stones without evidence of acute cholangitis at the time of ERCP and achieving complete stone clearance will be enrolled. Participants will be randomly assigned in a 1:1 ratio to prophylactic biliary stenting using a spontaneous dislodgement biliary stent or no stenting. Randomisation will be stratified by participating institution and maximum stone diameter (<10 mm vs ≥10 mm). The primary endpoint is the incidence of post-ERCP cholangitis within 7 days after ERCP, diagnosed using modified Tokyo Guidelines 2018 criteria adapted for post-ERCP conditions. Secondary endpoints include cholangitis severity, time to cholangitis onset, therapeutic antibiotic use, repeat ERCP or biliary drainage, ERCP-related adverse events and revisit or readmission within 30 days after ERCP. A total of 186 participants will be enrolled.

ETHICS AND DISSEMINATION: The study will be conducted in accordance with the Declaration of Helsinki and the Ethical Guidelines for Medical and Health Research Involving Human Subjects in Japan.The study protocol was approved by the Institutional Review Board of Yokohama City University Hospital on 11 May 2026. Additional approval will be obtained from participating institutions before study initiation.Written informed consent will be obtained from all participants.Study findings will be disseminated through peer-reviewed publications and scientific conferences.

TRIAL REGISTRATION NUMBER: jRCT1032260128.