The junction of the common bile duct, the main pancreatic duct and the duodenal papilla is a delicate structure in the body, which is regulated harmoniously by the combination of anatomical configuration, sphincter function, endocrine regulation and innervation. Anatomical variations in the biliary system are common, and the way in which the biliopancreatic ducts are connected varies widely among individuals. In approximately 85% of individuals, the common bile duct and the main pancreatic duct converge at an acute angle (41.4°±5.3°) in the inner segment of the duodenal wall to form a “common channel”, which is mostly between 4 and 12 mm in length and increases with age. The sphincter of Oddi surrounding the “common channel” controls and regulates the discharge of the common bile duct and pancreatic duct under the dual regulation of body nerves and body fluids to maintain the normal biliary and pancreatic secretion pressure and prevent the backflow of pancreatic and duodenal contents into the bile duct. If the bile ducts and pancreatic ducts converge at right angles outside the duodenal wall, making the “common channel” too long, it can lead to premature mixing of pancreatic juice and bile. The congenital developmental malformations caused by this condition are now considered to be a separate group of surgical disorders and can lead to a variety of related surgical disorders. We refer to this group of independent surgical disorders as pancreaticobiliary maljunction (PBM). PBM is clinically closely related to a variety of surgical diseases, broadly speaking: (1) malformations: such as congenital stenosis, atresia, diverticula, etc., especially congenital bile duct dilatation in pediatric patients (Babbitt proposed in 1969 that this disease is related to PBM, and since then many scholars have found that this disease is closely related to PBM through clinical observation and animal experimental studies) is one of the widely recognized causes. (2) Inflammation: Due to the presence of PBM, the pressure in the pancreatic duct is higher than the pressure in the bile duct, and the pancreatic juice flows backward into the bile duct, forming inflammation of the bile duct, or due to the increased pressure in the bile duct, which is greater than the pressure in the pancreatic duct, the bile flows backward’ into the pancreatic duct, forming pancreatitis, etc. (3) Tumors: including malignant tumors and very rare benign tumors, of which the incidence of biliary tumors is the highest. Our previous studies also confirmed the presence of misexpression of certain oncogenes (EGFR, COX-2) in patients with PBM. In Japan, Funabiki et al. reported the relationship between PBM and bile duct, gallbladder, and pancreatic cancers: the incidence of bile duct and gallbladder cancers in the Japanese PBM population was 10.4%, 285 times the risk in the general population, and even up to 800 times the risk in the bile duct alone. . It is evident that PBM is a high risk factor for combined biliopancreatic tumors. (4) Others: PBM has been shown to be closely related to biliary and pancreatic diseases such as bile duct stones, non-lithic cholecystitis and biliary pancreatitis. In summary, PBM is closely related to many surgical diseases. However, the diagnosis of PBM is a rather difficult clinical problem. It is generally accepted that PBM can be diagnosed in adults with a common channel length of ≥15 mm and in children with a common channel length of ≥5 mm; however, some individuals with a long common channel may not experience biliopancreatic reflux due to a sound terminal sphincter of the biliopancreatic duct, while some individuals with a normal confluence of the biliopancreatic duct may experience biliopancreatic reflux due to a weak terminal sphincter of the biliopancreatic duct. This makes PBM easy to be missed and misdiagnosed in clinical practice. At present, clinical surgeons are not sufficiently aware of PBM and do not pay high attention to it, which once made PBM the “forgotten corner of abdominal surgery” and made the diagnosis of PBM more difficult. In this paper, we review the clinical diagnosis of PBM, especially the current status of imaging diagnosis. I. X-ray diagnosis of PBM The signs of biliopancreatic reflux are often not clear in the upper gastrointestinal barium meal examination. In recent years, with the application of high-definition digital gastrointestinal machine, this sign is often seen in the upper gastrointestinal barium meal examination, but whether it has clinical significance has rarely been reported in the literature. This sign is mainly distinguished clinically from the descending duodenal diverticulum and duodenal papillary diverticulum. Barium X-ray examination of the upper gastrointestinal tract is noninvasive, inexpensive, less painful, and more acceptable to patients. However, its diagnostic specificity is still limited by the equipment and needs to be combined with other imaging examinations. Our previous study found that the incidence of PBM in patients with gallbladder stones was 7%. Li Yajun et al. collected more than 10,000 cases of upper gastrointestinal barium meal double imaging data, screened 96 patients with signs of biliopancreatic reflux, and compared and followed up with CT, ultrasound, laboratory tests and clinical, and diagnosed chronic pancreatitis in 58 cases (60.4%), acute pancreatitis in 2 cases (2.1%), and pancreatic cyst in 2 cases (2.1%); the positive rate was 64.6%. There were 34 cases without positive findings, accounting for 35.4%. This method has some reference value and can play a role in the screening of PBM. Second, ultrasound diagnosis of PBM B ultrasound is often used as the first choice for diagnosing biliary and pancreatic diseases because of its easy operation, non-invasive and inexpensive features, and its accuracy for gallbladder stones can reach 80%. However, ultrasound often misses more common bile duct lesions, especially those in the lower bile duct, due to images such as duodenal gas occlusion, and is also affected by the experience of the operator. In addition, the image of B ultrasound is tomographic and cannot directly display the image of the whole biliary erecta. Because of the limitations of ultrasound, the diagnosis cannot be confirmed clinically by this test alone. There are no direct signs of PBM diagnosed by ultrasound. The presence of PBM is often suggested by indirect signs. For example, if the presence of a cyst in the common bile duct is detected by initial clarification of bile duct dilatation, and ultrasound reveals a diffuse thickening of the gallbladder wall of 4 mm or more with a hypoechoic intramural layer, this suggests the presence of proliferative changes in the mucosa of the gallbladder and the possible presence of PBM. Therefore, the clinical diagnosis still needs to be clarified through a combination of ultrasound and other imaging tests to improve accuracy. CT is a widely used imaging test to diagnose PBM, but there are no reports of CT diagnosing PBM. CT is a tomographic image, unlike endoscopic retrograde cholangiopancreatography (ERCP), intraoperative or postoperative cholangiography, and magnetic resonance cholangiopancreatography (MRCP), which can show the whole picture of the pancreaticobiliary system on a single image. However, careful observation of multiple consecutive CT tomographic images of the head of the pancreas can diagnose PBM. There are two types of CT manifestations of PBM: (1) the direct confluence of the common bile duct and the main pancreatic duct is seen outside the duodenal wall, which is a direct sign; (2) the common bile duct and the main pancreatic duct are first arranged in a “double duct sign”-like arrangement, and on the subsequent tomographic images, they are one duct. This is an indirect sign. A thin-layer scan of the pancreatic head hook can be useful to see the direct sign. It is important to note that sometimes the two are first arranged in a “double duct sign” pattern and become one duct on the next tomographic image, but then the “double duct sign” appears again on the tomographic image below it. Therefore, CT diagnosis of PBM emphasizes the importance of looking at multiple levels in succession to make a diagnosis. In addition, the approximate length of the common channel can sometimes be calculated from CT images, and this also provides some clinical basis for diagnosis. However, in clinical practice, it is difficult to see the confluence of the common bile duct and the main pancreatic duct in the duodenal wall on CT images due to the volume effect, so CT examination has some limitations in diagnosing PBM. Fourth, MRCP diagnoses PBM MRCP is a non-invasive, non-contrast agent, non-operator technique, non-complication, and non-radiological damage to healthcare workers and patients imaging method. It can objectively reflect the natural state of the biliary and pancreatic duct system, and can display its anatomical structure completely, and the image can be rotated 360° to easily show the lesion, which has the superiority that other diagnostic methods cannot compare. The sensitivity of MRCP for bile-pancreatic duct dilatation and stenosis is 90%-95%, the diagnostic accuracy of the presence of common bile duct obstruction is 90%-100%, and the diagnostic accuracy of the localization of common bile duct obstruction is 85%-100%, and MPCP can clearly show the position of the common bile duct and main pancreatic duct and the confluence of common channels without inducing pancreatitis and causing damage to the sphincter of Oddi. Injury to the sphincter of Oddi. It is widely used clinically and easily accepted by patients. A retrospective analysis of MRCP in 24 cases of surgically or pathologically confirmed congenital bile duct dilatation by Liping Fu suggested that both intra- and extrahepatic bile ducts showed good clarity and manifested as single or multiple cystic, columnar, or cloacal bile duct limited dilatation inside and outside the liver. The diagnostic accuracy was 100%, which was significantly higher than the diagnostic rate of ultrasound and CT, and had a very reliable qualitative value. However, MRCP as a volumetric imaging method, the volume rate of fluid in the common channel is too small to completely show the duct imaging. In addition, the spatial resolution of MRCP is not sufficient, and the imaging technology and instrumentation conditions cannot completely replace other methods at this time. ERCP is a direct pancreatic and cholangiopancreatic angiography, which can clearly observe the entire pancreatic and biliary duct morphology and show whether the duct lumen is dilated, compressed, filling defect, stenosis, etc. It can show whether there are changes in the lumen such as dilatation, compression, filling defect and stenosis. Therefore, ERCP has an important diagnostic value for lesions in the biliopancreatic jugular abdomen, and it can also be used for biopsy, duodenal papillotomy on the basis of examination, endoscopic nasobiliary drainage, pancreaticobiliary dilation, and stent placement, which can replace some surgical procedures to some extent. Xu Xiaojiang et al. summarized 168 cases of biliary and pancreatic diseases examined by ultrasound, CT and ERCP, and the results suggested that ERCP was significantly more accurate than ultrasound and CT in the diagnosis of biliary and pancreatic tumor diseases. However, the fatal disadvantage of ERCP is that it is an invasive test, which is difficult to be used for screening, and it is even more difficult to operate in the face of young patients, and it may induce pancreatitis. This test requires a high level of operator skill, and inadvertent injury to the sphincter of Oddi during the procedure may aggravate the development of PBM. According to the literature, the incidence of injury to the biliopancreatic-intestinal junction after ERCP in China is 0.35% to 0.5%. The rest include acute pancreatitis (3.47%), upper gastrointestinal bleeding (1.34%), gastrointestinal perforation (0.6%), and duodenal perforation (0.3% to 1.3%). Sixth, ultrasound gastroscopy (EUS) diagnosis of PBM EUS is a new examination method combining two techniques of ultrasound and endoscopy, which avoids the interference of ordinary ultrasound by gastrointestinal gas and fat attenuation of the abdominal wall. The method also overcomes the defect that endoscopy cannot diagnose submucosal and extramucosal lesions and the depth of tumor infiltration. It can not only determine the site of obstruction, but also observe the obstructing lesion itself, which provides a new way for the diagnosis of combined biliopancreatic lesions. It does not require contrast injection during the operation, and the patient does not need to be exposed to radiation, which is especially suitable for pregnant women and patients who are allergic to contrast agents. The clinical application of EUS for the diagnosis of PBM has not been reported much, and it is mostly used for the diagnosis of other diseases of the biliopancreatic at present. The literature reports that EUS shows stones in the lower and middle segments of the common bile duct better than those in the upper segments. The diagnostic accuracy of EUS for lower bile duct stones is as high as 88.9%-94.0%, and the negative predictive value of EUS for pancreatic cancer diagnosis is as high as 100%. The diagnostic sensitivity for pancreatic cancer >3 cm in diameter can be as high as 100%, and most of the literature reports that the diagnostic sensitivity for pancreatic cancer less than 2-3 cm in diameter is significantly higher than that of CT. the diagnostic accuracy of EUS for pancreatic cancer ranges from 85% to 100%, which is also significantly higher than other examination methods. Meanwhile, the accuracy of EUS for T and N staging of pancreatic cancer was 78%-94% and 64%-82%. For duodenal papillary carcinoma, EUS can also be visualized by endoscopic images and the papilla can be biopsied if necessary. According to the literature, the accuracy of EUS for T and N staging of duodenal papillary carcinoma and jugular abdominal carcinoma is 74% and 63%. In addition, the diagnostic sensitivity of various imaging tests to determine the invasion of biliopancreatic cancer into the portal system is 95% for EUS, 85% for angiography, 75% for CT, and 55% for transabdominal ultrasound. Others include percutaneous hepatic puncture cholangiography, dynamic MRCP for pancreatic fluid secretion, digital 3D reconstruction technique, bile amylase examination, etc. Due to the limitations of each clinical application, not many of them are carried out at present. Finally, it is worth pointing out that PBM is only an anatomical abnormality, whereas the biliopancreatic-intestinal junction is a structural and functional unity. For this reason, the role of functional abnormalities of the sphincter of Oddi in the pathogenesis of biliopancreatic disease should not be underestimated. In some cases, although imaging suggests the presence of an overgrowth of the common channel, there are no clinical symptoms and no direct signs of pancreatic or bile reflux, which may be related to the functional soundness of the sphincter of Oddi. In some cases, on the other hand, although there are clear clinical symptoms and signs of pancreatic fluid and bile reflux, no common channel abnormality is found on imaging, which may likewise be due to the weakness of the sphincter of Oddi. The biliopancreatic-intestinal junction is finely anatomized and coexists structurally and functionally. Therefore, for the diagnosis of PBM, we need to rely on clinical + imaging to confirm the anatomical basis of common channel abnormality, but we also need to combine the functional evaluation of the sphincter of Oddi and actively look for direct signs of pancreatic fluid and/or bile reflux to further diagnose PBM at the three-dimensional level of anatomy + function.