Final answer:
Choledochal cysts are cystic dilatations in the common bile duct in children, and they are classified into five types. Type I is the most common type. These cysts can cause complications and require surgical treatment.
Step-by-step explanation:
Choledochal cysts are a type of cystic dilatation in the common bile duct in children. These cysts are classified into five different types, known as Todani classification, based on their anatomical features. Type I is the most common, accounting for about 80% of choledochal cyst cases in children.
The common bile duct is the structure formed by the union of the common hepatic duct and the gallbladder's cystic duct. Choledochal cysts can cause complications such as cholangitis, pancreatitis, and biliary obstruction. Surgical intervention is typically required to remove the cysts and reconstruct the biliary system.