A new variant of double common bile duct associated with choledochal cyst.

Extrahepatic bile duct duplication is a rare biliary anomaly often associated with conditions like cholecysto-choledocholithiasis, choledochal cyst and malignancy. Precise preoperative diagnosis using conventional radiologic imaging still remains a challenge and use of existing classification system is equally confusing. A female patient diagnosed with choledochal cyst by magnetic resonance cholangiopancreatography was found to have an associated new variant of double common bile duct during surgery. The variant discovered could not be classified by existing classification systems and was missed by preoperative imaging. Recognition of existence of this anomaly that warrants careful dissection during biliary surgery is necessary to avoid inadvertent biliary injury as preoperative diagnosis still remains a challenge. Review of existing classification systems is required to include newly discovered variants.