<prompt> Most commonly seen Choledochal cystType IType IIType IIIType IV  <response>: Most common Choledochal cyst Type IType IV Type III Type I is the most common It is the dilation of extrahepatic biliary tree Type Ia: cystic dilation Type Ib: Focal segmental dilation Type Ic : Fusiform dilation Treatment : Roux-en-Y hepatic jejunostomy Ref: Sabiston 20th edition 1510-1511 