The incidence of clostridial congenital bile duct dilatation has increased significantly in recent years. Because of its mild degree of bile duct dilatation, it is not easily distinguished from bile duct dilatation caused by bile duct sediment-like stones and roundworm remains, etc. Preoperative diagnosis is difficult, and the rate of missed diagnosis and misdiagnosis is relatively high. The treatment of clostridial dilatation is fundamentally different from that of bile duct dilatation caused by the above-mentioned causes, so a reasonable and standardized diagnostic process is of great importance for the diagnosis of clostridial congenital bile duct dilatation. The typical clinical manifestations of congenital bile duct dilatation are the triad of abdominal pain, abdominal mass, and jaundice, and according to the literature, the majority of patients have cystic bile duct dilatation. However, in recent years, with the improvement of medical conditions and diagnostic techniques, the proportion of patients with cystic bile duct dilatation has increased significantly. Cystic duct dilatation is not easily distinguished from simple bile duct dilatation caused by biliary roundworm remains and sediment-like stones, as no mass can be detected in the abdomen. Detailed medical history is the first clue to the diagnosis, children with clostridial dilation have a history of recurrent abdominal pain or abdominal discomfort, symptoms can be mild or severe, some children may have mild to moderate jaundice, blood white blood cell count is increased. The high pressure band formed by the sphincter of Oddi at the distal end of the common duct can lead to the reflux of pancreatic juice into the bile duct, and the trypsin, elastase and collagenase in it can damage the wall of the bile duct, making it weak and dilated; on the other hand, due to the increased pressure in the bile duct, the bile flows back into the pancreatic duct, leading to the activation of pancreatic enzymes and the development of pancreatitis. Pancreatitis occurs. Dilatation of the cisternal duct is usually combined with distal ectopic opening of the common duct and prolongation of the common duct. Since the opening of the common duct Vater’s jugular represents the site of early embryonic hepatic diverticula, the distal ectopic position of the hepatic diverticula during the embryonic period leads to elongation of the common bile duct and common duct. At the same time, congenital bile duct dilatation is often combined with abnormal pancreatic development and increased distance between the ventral and dorsal pancreas, which affects the fusion and development of the ventral and dorsal pancreas, resulting in pancreatic separation and increased angle of pancreaticobiliary confluence. Ultrasound is simple, non-invasive and inexpensive, and is often the first choice for diagnosing hepatobiliary and pancreatic diseases. CT has the advantage of fast scanning speed, which usually takes only a few seconds to complete the examination, so it is still the most commonly used examination method for pediatric hepatobiliary and pancreatic diseases, and ERCP has been recognized for its diagnostic value in biliary and pancreatic duct diseases, which can clearly observe the entire biliary and pancreatic duct morphology. However, the disadvantage of ERCP is that it is an invasive test, which is difficult to be widely performed and popularized in the face of young patients. MRCP is a non-invasive, non-contrast and non-radiographic imaging method. It can show the complete biliary and pancreatic anatomy, and the image can be rotated 360° to easily show the lesion, which has the superiority that other diagnostic methods cannot match. However, magnetic resonance examination takes a long time, and children who are too young usually cannot cooperate, so the examination cannot be carried out smoothly or the images are blurred to achieve the purpose of clinical diagnosis, so it is somewhat limited in clinical application. Intraoperative cholangiography is to inject the contrast agent directly into the gallbladder or bile duct to show the whole intra- and extrahepatic bile ducts and understand the nature and scope of the lesion, which is helpful for diagnosis. However, because intraoperative cholangiography is a paralleling contrast, if the sphincter of Oddi is relaxed or the opening of the pancreatic duct is edematous or narrowed, the contrast agent is quickly discharged into the duodenum and the pancreatic duct is sometimes poorly displayed. However, after improving the imaging method, such as increasing the injection pressure or increasing the distal resistance of the duodenal papilla, the imaging effect has improved. In addition, poor X-ray angles can also lead to unsatisfactory display of pancreaticobiliary cohesion. In conclusion, detailed history taking, selection of appropriate examination methods, application of standardized diagnostic procedures, combination of laboratory tests and imaging examinations, and careful analysis of relevant parameters can clarify the diagnosis of pediatric cloacal congenital bile duct dilatation, thus avoiding missed diagnosis and misdiagnosis.