This study is a multicenter, bidirectional cohort study aimed at continuously enrolling patients with biliary dilatation from 25 medical centers in China. It will collect comprehensive life-cycle data from the cohort to establish a Chinese cohort for bile duct dilatation. Based on this cohort, the study seeks to clarify the epidemiological characteristics, pathological features, standard classification, disease progression, cancer risk, and optimal timing for surgical intervention in patients with bile duct dilatation. Additionally, it will compare the perioperative risks, long-term outcomes, and quality of life among different types of patients (including Todani types I, IVa, and V) following surgical treatment, to establish standardized surgical treatment strategies for each type.

Biliary Dilatation(BD) is a complex benign biliary disorder prevalent in East Asia, for which surgical resection remains the sole curative approach necessitating prompt intervention upon diagnosis. Nevertheless, critical aspects including disease subtyping, standardized surgical management protocols, and prognostic determinants remain inadequately defined. This multicenter ambidirectional cohort study aims to consecutively enroll BD patients across 25 tertiary medical centers in China, systematically collecting comprehensive life-cycle data encompassing demographic profiles, clinical baseline characteristics, laboratory/imaging findings, biliary-specific biomarkers, and longitudinal follow-up records to establish a nationally representative Chinese BD cohort. Building upon this cohort, the study objectives are structured as follows:

1. Establishment and Maintenance: To construct and perpetually update a multicenter clinical database for BD research in China, ensuring data integrity and accessibility.
2. Age-Stratified Comparative Analysis: To delineate and contrast the differential patterns of disease progression, surgical decision-making paradigms, and postoperative surveillance strategies between adult and pediatric BD populations.
3. Natural History Characterization: To elucidate disease trajectories, morphological evolution, comorbidity progression, malignant transformation risks, and evidence-based surgical indications/timing in non-operated asymptomatic BD patients.
4. Therapeutic Standardization: To define optimal surgical modalities (with emphasis on Todani classification types I, IVa, and V) and critically evaluate the efficacy-safety profile of standardized operative approaches through multidimensional outcome assessments.
5. Quality-of-Life Quantification: To systematically evaluate postoperative quality of life (QoL) metrics across BD subtypes and identify modifiable determinants influencing long-term patient-reported outcomes.
6. Epidemiological Benchmarking: To synthesize epidemiological patterns, establish evidence-based clinical endpoints for surgical interventions, and define reference standards for treatment-related risks and QoL benchmarks in standardized BD management.

Inclusion Criteria:

1. Patients who have been definitive diagnosed with biliary dilation.
2. Patients aged between 0 and 80 years old, regardless of gender.
3. In line with the principle of informed consent: For the retrospective cohort of biliary dilation, exemption from signing the informed consent form is applied for, while for the prospective cohort, signing the informed consent form is required.

Exclusion Criteria:

• None

All patients with a definitive diagnosis of biliary dilation in the participating centers will be included.