The management of congenital biliary dilations (CBDs), including choledochal cysts, represents one of the most challenging areas in hepatobiliary surgery due to their potential implications for long-term morbidity and malignant transformation. While CBDs have a relatively low incidence in Western populations (1/150,000-1/100,000), the prevalence is notably higher in Asian countries (1/1,000), making it a significant global health concern. Although complete surgical resection remains the standard of care, the optimal extent of resection and reconstruction strategy, particularly for complex disease patterns, continues to be debated. To address these challenges, the current study proposes a novel surgery-oriented classification system for adult CBD based on the analysis of 234 consecutive cases.

Inclusion Criteria ：

1. Age: Adults (≥18 years).
2. Study population: Consecutive patients treated at Beijing Tsinghua Changgung Hospital.
3. Time frame: Underwent surgical treatment between November 2014 and October 2024.
4. Condition/Procedure: Underwent surgical treatment for common bile duct (CBD) diseases.
5. Diagnostic confirmation: Presence, location, and extent of CBD dilatation were diagnosed by preoperative imaging/radiology, and confirmed intraoperatively. Exclusion Criteria ：

1.Secondary biliary dilatation due to proximal obstruction, including intrahepatic and/or extrahepatic bile duct dilatation caused by proximal biliary obstruction, such as:

1. benign stricture,
2. malignant stricture,
3. obstructive stones.

Consecutive adult patients who underwent surgical treatment for common bile duct (CBD) diseases between November 2014 and October 2024 at Beijing Tsinghua Changgung Hospital.