Choledochal cyst is a common congenital anomaly in children (1). It is more prevalent in the Asian population, with an incidence rate of approximately one in ten thousand. It typically presents as dilation of the common bile duct, with or without concurrent intrahepatic bile duct dilation. The standard curative approach involves cyst excision along with hepaticojejunostomy using Roux-en-Y anastomosis (2). Currently, it is believed that the pathogenesis of choledochal cyst is based on the pancreaticobiliary maljunction (PBM) (3). The convergence of the bile and pancreatic ducts outside the wall of the duodenum leads to an excessively long common channel. Dysregulation of the Oddi sphincter disrupts the fluid dynamics stability of bile and pancreatic secretions, causing widespread pancreatic fluid reflux into the common bile duct, further leading to chronic inflammation of the bile ducts and ultimately increasing the risk of bile duct cancer (4).

Minimally invasive surgery has been widely used in the treatment of children with choledochal cyst. Children with choledochal cyst may experience various complications before surgery, such as bile duct obstruction, cholangitis, bile duct perforation, and pancreatitis (5). Once these complications occur, they often lead to the postponement of definitive surgery or necessitate emergency open surgery. Additionally, local inflammation and other factors increase the difficulty of minimally invasive surgery (6, 7). Therefore, there is not yet a fully unified consensus on the timing of definitive surgery for children with choledochal cyst who present with preoperative complications.

Endoscopic retrograde cholangiopancreatography (ERCP) is an important diagnostic and therapeutic method for biliary and pancreatic diseases, and its minimally invasive nature and effectiveness have led to its rapid development (8, 9). ERCP procedures are often challenging in pediatric patients, and specific guidelines for their use have not yet been established (10). However, ERCP has gradually been widely used in the diagnosis and treatment of pediatric hepato-biliary-pancreatic diseases. For the diagnosis of PBM (pancreaticobiliary maljunction) in children with choledochal cyst, ERCP is more accurate than ultrasound and magnetic resonance cholangiopancreatography (MRCP) (11, 12). However, due to the requirement for general anesthesia in pediatric ERCP procedures, most doctors do not recommend performing diagnostic ERCP alone in children. This study aims to explore the safety and effectiveness of ERCP in treating preoperative complications of choledochal cyst in children and the timing of definitive surgery after ERCP.

Children with choledochal cyst may experience various complications such as pancreatitis, cholangitis, bile duct perforation, and malignant transformation. These types of choledochal cyst are also known as complex choledochal cyst. The occurrence of complications can affect the prognosis of later treatment. However, standardized approaches for managing complex choledochal cyst have not yet been established. Additionally, the timing of surgery following complication treatment is also an area worthy of exploration. The existing ERCP guidelines are still incomplete with regard to pediatric patients (13). In some pediatric ERCP guidelines, the use of ERCP as a diagnostic tool alone is not recommended (14). Therefore, in this study, all ERCP procedures were therapeutic. In this study, we focused on the two most common complications, pancreatitis and biliary obstruction combined with biliary infection, to investigate the safety and effectiveness of ERCP in treating cyst-related complications. Although children with choledochal cysts complicated by simple pancreatitis can recover with conservative treatment, the waiting time for definitive surgery after pancreatitis is relatively long, and there is a risk of recurrent pancreatitis.

Due to the presence of PBM, pancreatic juice is prone to reflux, leading to the formation of protein plugs in the bile ducts. Protein plugs formed within the common channel ultimately result in the occurrence of pancreatitis (15). According to various reports, the incidence of pancreatitis can range from 5% to nearly 70% (16, 17). Unlike adults with pancreatitis, children with choledochal cyst rarely develop severe pancreatitis. They generally respond well to conservative treatment (18). Although there is no unified guideline for the indications of ERCP in children, it is gradually playing an important role in the diagnosis and treatment of various pediatric pancreatitis cases. ERCP holds high diagnostic and therapeutic value for potential PBM and other pancreatic duct abnormalities. In this study, apart from one case with unsatisfied post-ERCP outcome, the clinical symptoms and elevated amylase levels of the other children with cyst-related pancreatitis were significantly relieved. Additionally, ERCP has significant advantages in managing protein plugs within the common channel, shortening the course of pancreatitis, and laying the foundation for the treatment of the common channel during definitive surgery.

Among the infectious complications of choledochal cyst, cholangitis is common (19), especially in adults with choledochal cyst (20). The exact cause of cholangitis remains unclear, with reports indicating a higher incidence in type 4a choledochal cyst (20). Some patients may respond well to broad-spectrum antibiotics, but there are still some who require timely drainage to relieve obstruction and prevent the adverse consequences of acute suppurative cholangitis. Currently, there are various methods for biliary drainage, including percutaneous drainage or endoscopic drainage (21–23). With the development of pediatric ERCP, its safety and effectiveness have led to more centers opting for ERCP to relieve biliary obstruction. There are no unified guidelines for the diagnosis and treatment of biliary obstruction complicated by cholangitis in pediatric ERCP. Whether ERCP is superior to conservative treatment in terms of treatment success for children with concurrent cholangitis needs further clarification through clinical trials. In this study, all 27 children with choledochal cyst complicated by biliary obstruction received effective treatment, and their symptoms and liver function index showed significant improvement compared to before treatment.

In this study, we did not include patients with type 2 PBM. Patients with type 2 PBM do not have obvious dilation of the bile ducts, and the proportion of symptom occurrence is relatively low. Symptoms also appear later in these patients, so a significant number of type 2 PBM patients often develop the disease in adulthood (24). There is still controversy regarding the treatment of these patients. Whether incidentally discovered PBM requires definitive surgery remains inconclusive. Some researchers believe that surgery is necessary for these patients to avoid symptom occurrence and potential cancer risks. Conversely, others propose that asymptomatic type 2 PBM patients only require observation and follow-up. Additionally, there is ongoing exploration into whether ERCP can avert further surgery in symptomatic type 2 PBM patients (25). The short-term results indicate that ERCP cannot completely prevent symptom recurrence and subsequent definitive surgery (26).

During the inflammatory phase, severe local adhesions can pose challenges to surgery. There is no unified conclusion on how long after inflammation control surgery should be performed. Previous reports suggest that performing surgery 6–8 weeks after inflammation control may be appropriate (6). ERCP can effectively alleviate the symptoms of bile duct cyst, so we speculated whether ERCP could shorten the waiting time for surgery. In recent years, our center generally schedules definitive surgery 1–2 weeks after ERCP. Therefore, we compared the short-term prognosis of patients undergoing surgery at different times, using 2 weeks after ERCP as the dividing point. The results indicate that there is no significant difference in the short-term prognosis between the two groups of patients. Therefore, early definitive surgery after ERCP is safe and feasible. Nevertheless, it is important to highlight that there were 2 cases requiring conversion to open surgery in the early surgery group, and the average blood loss along with the number of transfusion cases were higher compared to those in the late surgery group. While this difference did not reach statistical significance, it implies that the early stage of inflammatory recovery might present challenges during surgery.

Pediatric ERCP can have complications such as PEP, perforation, bleeding, etc., and the occurrence of complications can prolong the hospital stay of children and delay curative surgery. PEP is the most common complication, with an overall incidence rate of approximately 5%–20% (27). PD injection, cannulation and EST, anatomic factors such as pancreas divisum, and patient related factors such as a prior history of PEP and genetic factors may be high-risk factors for PEP (28, 29). In this study, one case of children with biliary obstruction developed PEP, showing elevated amylase levels and worsened abdominal pain after ERCP. This child recovered after conservative treatment. The overall incidence rate of PEP was 1.50% (1/68). Excluding children with pancreatitis as the presenting symptom, the incidence rate of PEP was 3.70% (1/27), which is considerable with other literature reports. According to our center's experience, unlike adults, the incidence of severe post-ERCP pancreatitis in children is lower, and there is still no consensus on preventive measures for postoperative pancreatitis. Further research is needed on the use of preventive drugs such as nonsteroidal anti-inflammatory drugs. In this study, we routinely performed EST on the children. Previous studies have suggested that EST is associated with PEP (29), and as a result, the use of EST in pediatric ERCP has not reached a consensus (30). Additionally, there is a lack of long-term follow-up data to assess the long-term effects of EST on children. Some scholars believe that EST can be considered a standard procedure in children with biliary obstruction and cholangitis (31). In our study, among the 41 children with preoperative pancreatitis, 36 cases had elevated γ-GT and abnormal liver function. We have reason to believe that these children also had biliary obstruction, and the use of EST did not significantly increase the incidence of short-term complications. Future studies with large sample sizes and prospective designs are needed to determine the indications for EST.

This study still has some limitations. Firstly, it is a retrospective study with a relatively small sample size, leading to potential bias in case selection and clinical data collection. Secondly, curative surgeries in this study were performed by multiple surgeons, resulting in certain differences in the timing and methods of surgery following ERCP. Thirdly, based on the data from this study, early surgery after ERCP does not affect the short-term prognosis of pediatric patients. However, whether it affects the occurrence of long-term complications such as intrahepatic bile duct stones, anastomotic strictures, etc., still requires further investigation. Additionally, although we believe that the use of ERCP can provide early definitive surgery for some children with complex choledochal cysts, we did not select children with complex choledochal cysts who had not undergone ERCP treatment as a control group in this study. In the future, we need to design prospective studies and establish multiple control groups to validate our conclusions. Meantime, We only discussed the two most common complications in this study. There is limited research on the treatment of other rare complications with ERCP. Spontaneous bile duct perforation is a rare but serious complication that often requires emergency surgical treatment with cholecystostomy. Portal hypertension is also one of the severe complications of choledochal cyst, and surgery is the only curative method. However, there are reports suggesting that ERCP may serve as one of the treatment options for alleviating symptoms in patients before surgery (32). Finally, the use of ERCP involves several high-cost consumables, which, while providing clinical benefits to patients, also increases their financial burden to some extent. However, the study did not compare the total hospitalization costs and duration.

In summary, ERCP can safely and effectively alleviate preoperative complications in pediatric patients with choledochal cyst. Early definitive surgery following ERCP does not increase intraoperative risks or postoperative complication rates in pediatric patients. However, further research is needed to investigate the long-term effects of ERCP on pediatric patients with complex choledochal cyst. Additionally, indications for ERCP in pediatric patients with choledochal cyst still require clarification through large-sample prospective studies.