A 5-month-old child with congenital choledochal cyst was admitted to our department and underwent successful cyst removal surgery. The 5-month-old baby girl, Susanna, is a pretty and cute little girl. Recently, her parents found that her stomach was gradually increasing, but it did not attract their attention. 10 days ago, her baby had crying and fever, and she was seen in the nearest hospital. The doctor considered an upper respiratory tract infection, and she was given anti-inflammatory treatment, but she did not feel better. The child’s face gradually turned yellow, stools began to whiten. After detailed examination, the child was found to have a large abdominal mass, occupying most of the child’s abdomen, which was diagnosed as congenital choledochal cyst by ultrasonography. The child was diagnosed with congenital choledochal cyst by ultrasound examination. The child was admitted to General Surgery Department C with “congenital choledochal cyst combined with infection”. After anti-inflammatory treatment, the child’s temperature gradually subsided, jaundice improved, and the child was prepared for surgery. Niu Jianxiang, Department of General Surgery, The Affiliated Hospital of Inner Mongolia Medical University Congenital choledochal cyst, also known as congenital cystic dilatation of the common bile duct. Clinical data show that the incidence of congenital choledochal cysts is higher in Asians than in Europeans and Americans, especially in infants and children, which accounts for 2/3. The disease is usually due to abnormalities of the choledochal duct caused by biliopancreatic merging. Without surgical treatment, the disease is often fatal due to recurrent infections, biliary cirrhosis, perforation of the common bile duct, or carcinoma. Therefore, when the disease is definitely diagnosed, the child should be operated promptly: (1) The main purpose of the operation is to restore the drainage of bile into the intestines so as to avoid the occurrence of ascending cholangitis. (2) The dilated common bile duct should be removed to prevent future cancer. (3) To prevent future anastomotic stenosis. Currently, the commonly used surgical methods are: (1) cyst resection, common hepatic duct jejunum Roux-Y anastomosis. (2) Resection of the cyst, jejunojejunal interposition instead of biliary surgery. (3) cyst duodenal anastomosis and cyst resection of the common hepatic duct duodenal anastomosis, this method is difficult to prevent reflux infection and anastomotic stenosis, so it is less used at present. Surgery for choledochal cysts is a difficult surgery in the field of pediatric surgery. The choledochal duct is adjacent to the hepatic artery, gastroduodenal artery, portal vein, duodenum, pancreas and other important blood vessels and organs, and damage to any one of these tissues will lead to unsuccessful postoperative recovery and even serious complications. Preoperative discussions were held before the operation under the leadership of Director Wang Wanxiang. The child was a 5-month-old girl, weighing only 7 kilograms, and the diameter of the choledochal cyst was more than 4.4 cm, occupying half of the child’s abdominal cavity, and there was a recent infection, and the jaundice had not completely subsided, which posed a great risk for the surgery. However, without surgery, the child’s choledochal cyst may perforate or rupture at any time, and the child’s life will be seriously threatened by these complications. Some doctors have suggested that the child’s low weight, large cyst, recent severe infection, and the close adhesion of the choledochal cyst to the surrounding blood vessels would make the surgery risky because of the severe bleeding that would occur from the large cystic wound during the surgery. The conventional and safe treatment is to first open the abdomen to take the external drainage of the choledochal cyst, and then perform radical surgery after three months. This type of surgery is a traditional and conservative treatment option. However, it can have a great impact on the child and the family. Drainage of bile out of the body can cause maldigestion, malabsorption, electrolyte disorders and biliary tract infections, and the child is often hospitalized for electrolyte disorders. The two surgeries will also cause heavy financial pressure on the child’s family. Some doctors suggested that the operation method can be decided according to the intraoperative situation, if the inflammation is not heavy to choose a one-time radical surgery, the surgical method to choose the open surgery, because the cyst is too large, the inner has exceeded the midline of the abdomen, the lower has been close to the lower abdomen, the operation space is too small; in addition, the child is small, low weight, the operation time is too long on the child’s postoperative recovery will bring great impact. On the morning of August 20, the child was sent to the operating room, where Director Wang Wanxiang started the operation with the cooperation of Deputy Director Ren Jianjun, Attending Physician Niu Jianxiang, and the operating room and anesthesiology department. During the operation, it was found that most of the abdominal cavity was occupied by a huge cyst, and the duodenum was pushed up against the anterior wall of the cyst. After carefully separating out the intestinal tube, about 800ml of bile and a large number of sediment-like stones were extracted by puncture, and the operation was carried out in the child’s narrow abdominal cavity. After 4 hours of hard work, the child’s gallbladder was carefully removed, and then after carefully removing the choledochal cyst, the bile duct was reconstructed, and finally the anastomosis of the child’s gastrointestinal tract was restored. Bleeding was 10 ml during the operation, and the child recovered well after the operation, started to eat after 3 days, and was discharged from the hospital on the 8th day. Two weeks later, the jaundice completely subsided and all biochemical indicators were normal, and the child became a lively and lovely baby again. Although the child had his gallbladder removed, it will not affect his health in his future growth. Choledochal cyst is a congenital developmental abnormality, and there are many different theories about its etiology, among which the abnormality of pancreaticobiliary duct connection has been confirmed. Children suffering from this disease should seek early medical attention without too much delay, otherwise cirrhosis can occur gradually from obstructive jaundice due to biliary tract infections. We did not review the minimum age recorded in the foreign literature (the disease is relatively rare in Western countries). In a large group of domestic surgical cases, the minimum age of the child was 4 months.