This study is a multicenter, ambidirectional cohort study aiming to consecutively recruit asymptomatic biliary dilation patients incidentally discovered by imaging from 25 medical centers across China. The investigators will collect comprehensive clinicopathological data from the cohort to evaluate the epidemiological characteristics of asymptomatic patients, the distribution of Todani classifications, common imaging-detected comorbidities, and natural history; and, based on high-quality evidence, assess whether surgical intervention can improve the prognosis of asymptomatic patients, thereby providing a basis for developing targeted surveillance and intervention strategies.

Biliary dilation (BD) is a common and complex benign biliary disorder, for which surgical resection remains the only definitive treatment. However, while there are numerous studies on symptomatic BD, there is a lack of systematic, reliable data that describing the population structure, complication rates, comparing natural history and postoperative outcomes of patients whom incidentally detected by imaging and have no biliary symptoms. This multicenter, ambidirectional cohort study aims to consecutively recruit asymptomatic BD patients from 25 tertiary medical centers across China and to systematically collect their clinicopathological data-including demographic characteristics, baseline clinical features, laboratory and imaging results, biliary specific biomarkers, and longitudinal follow up records-in order to establish an asymptomatic subcohort within the larger China BD cohort. Based on this subcohort, the research objectives are structured as follows:

1. Database Establishment and Maintenance: Construct and continuously update a multicenter clinical database for asymptomatic BD patients in China, ensuring data completeness and accessibility.
2. Epidemiological Characterization of Asymptomatic BD: Describe the epidemiological features of asymptomatic BD patients, including demographic profiles (age, sex), distribution of Todani classifications, incidence of various complications, and risk of malignant transformation.
3. Comparison of Surgical Treatment Versus Conservative Observation: Compare key clinical outcomes between asymptomatic BD patients who undergo surgical intervention and those managed by medical observation, thereby providing evidence-based guidance for clinical decision making in this population.

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:

-

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