Management of adult congenital biliary dilatation (CBD) lacks standardized surgical guidance, particularly for complex intrahepatic and intrapancreatic involvement. Traditional anatomical classifications inadequately address modern surgical decision-making needs. This study aimed to develop and validate a surgery-oriented classification system that guides precise surgical approaches for adult CBD.

A classification system was developed based on anatomical characteristics, disease extent, and corresponding surgical approaches in 234 patients with CBD. Surgical procedures guided by the classification system included hepatectomy, biliary reconstruction, and liver transplantation. The long-term surgical outcomes and perioperative complications were analyzed.

The classification system categorized 234 patients with CBD into the following 4 types with 2 subtypes: Type A-peripheral intrahepatic (12 patients [5.1%]), Type B-central intrahepatic (5 [2.1%]), Type C-extrahepatic (45 [19.2%]), and Type D-combined intra- and extrahepatic (172 [73.5%]). Classification-guided surgery achieved excellent and good outcomes in 84.5% of cases. Major complications (Clavien–Dindo grade ≥ Ⅲ) occurred in 33 (14.1%) patients. Three-year disease-free survival was 71.4%, 100.0%, 89.3%, and 63.0% for Types A to D, respectively (p = 0.026). Type D2 patients, defined as having the most complex disease patterns, had the worst outcomes (3-year disease-free survival: 61.6%).

Our surgery-oriented classification effectively stratified adult CBD and guided the selection of surgical approaches. It shows particular value in managing complex disease patterns, although patients with combined intra- and extrahepatic involvement require careful consideration relative to the extent of surgical management. The standardized approach and validated outcomes of this classification suggest potential for widespread adoption in global surgical practice.