Through the experience of large number of cases in recent years, people tend to unify the treatment methods for choledochal cysts. Internal cyst drainage and cystectomy hepatic duct duodenal anastomosis, which were used in the past to treat children with choledochal cysts, have been abandoned due to the high incidence of postoperative complications such as intracapsular infection, anastomotic stricture, stone formation, gastric reflux and even carcinogenesis. It is now advocated that complete resection of the cyst by hepatic duct-jejunostomy Roux-Y anastomosis is the standard procedure for the radical treatment of choledochal cysts, regardless of the age of the child or the severity of the symptoms. Preoperative and intraoperative detailed understanding of the alterations of the whole pancreaticobiliary system of the child, as well as dealing with the abnormal lesions of the intrahepatic bile duct and pancreatic duct and common duct, is the key to reduce postoperative complications. 1.Complete cystectomy In infants and children with short history, cystic dilatation of the common bile duct is common, the cyst wall is usually very thin, the inflammation around the portal vein is light, and the tissue adhesions are not heavy, so complete excision of the whole cyst is feasible. If the child has a long medical history and repeated cyst infection, the cyst may sometimes have serious adhesions with the surrounding area, and the anatomical level is unclear, so the cyst may bleed a lot if the whole layer is removed, and there is even the possibility of damaging large blood vessels and pancreatic tissues, so endoscopic resection of the cyst can be performed, while avoiding the freeing of the cyst wall. 3.Cyst external drainage For cases of biliary perforation causing biliary peritonitis, severe cholangitis and difficult cyst removal due to poor systemic condition of the child, external cyst drainage is feasible to solve the problem of biliary obstruction in order to reduce the blow to the child, and after the child’s condition improves, radical surgery will be performed again. Open cyst drainage, percutaneous puncture of the cyst or bile duct drainage are effective and optional methods. 4. Management of intrahepatic bile duct stenosis It is currently believed that postoperative cholangitis and intrahepatic bile duct stone complications are not due to reflux, but to obstruction of bile outflow and bile duct dilatation caused by intrahepatic bile duct stenosis. Bile duct stenosis usually leads to dilatation of the proximal bile duct, and if the stenosis is not corrected intraoperatively, postoperative complications such as cholangitis and intrahepatic bile duct stones will result. It is currently advocated that the stenotic lesion leading to intrahepatic bile duct dilatation should be treated intraoperatively and intrahepatic bile duct stones should be removed at the same time. 5. Management of common duct and pancreatic duct abnormalities With the improvement of diagnostic imaging and the application of endoscopy of the pancreaticobiliary system, there are more and more reports of combined pancreaticobiliary common duct with protein embolus or stones, distal stenosis of common duct, stenosis and dilatation of pancreatic duct and pancreatic duct malformation. Many scholars believe that protein emboli in the bile duct, pancreatic duct and common duct are the direct cause of the symptoms of common bile duct cysts [3], which are rare in children less than one year old. The combination of history, preoperative MRCP, CT and intraoperative cholangiography can establish the diagnosis of most protein emboli in the common bile duct and common duct. However, cholangioscopy is still considered to be the most reliable method for diagnosis. Pediatric urethroscopy can be used instead of cholangioscopy to examine the intraoperative biliary system in children. A large number of case reports showed that 11.9% of children had stones or protein emboli in the distal part of the common pancreaticobiliary duct, and such children often had a combination of overgrown and dilated common pancreaticobiliary duct with acute pancreatitis before surgery. Stones in the common pancreaticobiliary duct cause recurrent abdominal pain and pancreatitis, and if they are not removed during surgery, they may turn into stones in the pancreaticobiliary system and lead to recurrent postoperative cholangitis and pancreatitis. Common intraductal stones can be effectively removed by intubation with saline flushing and direct visual flushing with choledochoscopy or urethroscopy. Rarely, intrapancreatic pancreatic duct stenosis causing distal pancreatic duct dilatation and stones requires pancreatic duct dissection along the main pancreatic duct and establishment of lateral anastomotic drainage of pancreatic duct jejunum; distal stenosis of common duct causing common duct dilatation can be treated by duodenal papillotomy and angioplasty. 6.Biliary reconstruction Complete resection of the cyst hepatic duct jejunostomy Roux-Y anastomosis is now the standard procedure for treatment, and interjejunal placement hepatic duct duodenal anastomosis is more complicated in operation and has no obvious advantages, and has been abandoned. Treatment of non-biliary duct dilatation pancreaticobiliary flow abnormalities Children with a history of recurrent pancreatitis should be highly suspected of having combined pancreaticobiliary flow abnormalities even if the common bile duct is not dilated. Non-biliary dilated pancreaticobiliary anomalies are not uncommon in clinical practice, and in the past, it was controversial whether to treat them surgically. Children with abnormal pancreaticobiliary syncope without common bile duct dilatation often present with abdominal pain, similar to pancreatitis, with increased serum pancreatic amylase, and in some cases, intermittent jaundice or white stools, or even biliary perforation. In 37% of children with non-biliary dilated pancreaticobiliary syndromes, protein emboli or stones were present in the common duct, while only 16% of children with biliary dilated common bile duct cysts had a combination of bile emboli in the common duct. Although the bile ducts are not dilated, the pancreaticobiliary system has the same pathological changes as common bile duct cysts, and untreated cysts can lead to the same serious complications as common bile duct cysts, such as pancreatitis, cholangitis, stones, bile duct perforation, and especially gallbladder cancer. Although the bile ducts are not dilated, in cases of pancreatic fluid reflux, chronic gallbladder inflammation and protein embolism due to abnormal pancreatic-biliary cohesion, the pancreatic and bile ducts must be surgically separated, and only then can serious complications be prevented. As with the treatment of common bile duct cyst, complete resection of the gallbladder and common bile duct with hepatic duct jejunojejunal Roux-Y anastomosis is a reliable procedure for the treatment of non-biliary dilated pancreaticobiliary syndromes. 8. Intraoperative choledochoscopy Many scholars now advocate routine intraoperative endoscopy of common duct, pancreatic duct and intrahepatic bile duct to directly understand whether there are stones and strictures in the pancreaticobiliary system, as well as flushing the duct with saline and removing stones. After cyst removal, intraoperative endoscopy using pediatric cystoscopy or laparoscopy can determine the level of common hepatic duct transection. Intraoperative biliary endoscopy helps to show the lesions in the bile duct for safer removal of the cyst. 9. Application of laparoscopy for the treatment of common bile duct cyst With the maturity of laparoscopic surgery, it has been applied for the treatment of common bile duct cyst since 1995. The technique has matured and is widely adopted by famous pediatric surgery centers at home and abroad, showing that the procedure has the advantages of small blow, fast recovery, beautiful incision, especially the magnification effect of laparoscopy facilitates bloodless peeling resection and accurate anastomosis of the cyst. Laparoscopy can achieve complete resection of cysts, enlargement and shaping of stenosed hepatic ducts, and removal of proteinaceous stones from intrahepatic bile ducts and common ducts, but intrahepatic hepatic segmental biliary stenosis, stones in pancreatic ducts, secondary surgery and recurrent chronic peribiliary inflammation are still considered contraindications to laparoscopic surgery. Laparoscopic radical treatment of congenital common bile duct cysts will certainly become the standard procedure for the treatment of common bile duct cysts, but the success of this procedure requires surgeons to have extensive experience not only in open surgery, but also in laparoscopic surgery operations. With the development of minimally invasive techniques, single-port laparoscopic techniques are gradually becoming a new trend in the current treatment of pediatric surgical diseases. However, there are fewer reports on single-port laparoscopic treatment of common bile duct cysts at present. 10. Treatment of choledochal cysts in newborns With the improvement of prenatal diagnosis technology and wide application, more and more cases are clearly diagnosed in the fetal period. The treatment is not fully unified yet. For suspected choledochal cysts in newborns, they should be closely observed after birth, and liver function and ultrasound examination should be performed regularly every month. If there is no discomfort, normal bilirubin and transaminases, and no significant changes in the size of the cyst, radical surgery can be observed until 3-6 months, and cystectomy should not be performed in the neonatal period as much as possible; if the child has abdominal pain, vomiting, jaundice or even white stools, abnormally high bilirubin and transaminases, or the diameter of the cyst increases, or if it cannot be distinguished from type I biliary atresia, radical surgery should be performed immediately treatment, otherwise the liver function of the child will be impaired and even develop into cirrhosis. Because of the heavy biliary obstruction lesions in newborns, severe edema and adhesions are often combined around the cysts, which makes surgery delicate and difficult, requiring experienced pediatric surgeons to perform the surgery. In the treatment of choledochal cysts, laparoscopic surgery should be preferred because, on the one hand, the surgical blow is small, the child recovers quickly, and the wound is aesthetically pleasing. On the other hand, laparoscopic radical choledochal cyst surgery has become a mature and safe treatment technique.