Choledochal Cyst. In: Doherty GM. eds. Quick Answers Surgery. McGraw-Hill; Accessed April 02, 2021. 

• Type I cysts (fusiform dilation of common bile duct [CBD]) account for 85-90%
• Type II (true diverticula of CBD) 1-2% of cases
• Type III (choledochocele—dilation of distal/intramural portion of CBD) < 2% of cases
• Type IV (multiple cysts involving intrahepatic and extrahepatic ducts) as high as 15% of cases in some series
• Type V (cystic malformation of intrahepatic ducts) rare
• 3-5% incidence of carcinoma