Prenatal biliary imaging for the diagnosis of biliary atresia: a protocol for a multicentre prospective diagnostic accuracy study.

introductionBiliary atresia (BA) is a rare but serious infantile cholangiopathy requiring timely diagnosis and surgical intervention. However, current screening methods are limited by their postnatal initiation. By contrast, antenatal imaging is increasingly considered promising due to growing evidence of a prenatal onset of BA, although high-quality diagnostic evidence remains scarce. This study aims to evaluate the diagnostic performance of antenatal biliary imaging features for the detection of BA. METHODS AND ANALYSIS: This is a multicentre, prospective cohort diagnostic accuracy study enrolling pregnant women undergoing routine prenatal ultrasound. The index test consists of predefined imaging features of the fetal biliary system. A minimum of 92 082 pregnancies will be screened and a dual follow-up strategy has been designed to balance feasibility and diagnostic rigour. All fetuses with positive index test findings, along with a 1:1 systematically sampled group of test-negative cases, will be included in a direct follow-up subset. The remainder will undergo indirect follow-up through health system linkage and outcome verification. The reference standard for diagnosing BA is based on postnatal clinical follow-up, supplemented by surgical exploration and intraoperative cholangiography when deemed necessary. Diagnostic performance will be assessed by calculating sensitivity, specificity, positive and negative predictive values. ETHICS AND DISSEMINATION: The study has been approved by the Ethics Committee of Children's Hospital of Fudan University (number 2024-30). Findings will be disseminated through academic conferences and submitted for publication in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ChiCTR2400087744.