When biliary atresia is suspected, the following tests can be performed. 1, dynamic observation of serum bilirubin: because biliary atresia is a complete obstruction of the bile duct, the level of serum bilirubin will be continuously high and unchanged or progressively increasing, up to 60~390μmol/L. When the direct bilirubin exceeds 50%, biliary atresia should be highly suspected, and dynamic observation should be repeated at least once a week for liver function. 2, ultrasonography: ultrasonography is the most common method of initial screening. If the gallbladder is well developed and can shrink to about 50% of its original volume after eating, it is considered a high possibility of hepatitis. In biliary atresia, the gallbladder is empty and deflated as a long narrow sac, or the gallbladder cannot be detected (there is some diagnostic significance by comparing the size of the gallbladder before and after meals). Yang Lucheng, Department of Pediatric Surgery, Zhujiang Hospital, Southern Medical University 3. Duodenal drainage fluid analysis: theoretically, biliary atresia can be ruled out when a drainage tube is placed in the duodenum and the fluid drawn out is yellow and the test contains bilirubin. However, it seems difficult to ensure that the catheter reaches the duodenum, and although pediatric gastroscopy techniques may be helpful, they are used more rarely in clinical practice. 4.Radionuclide imaging: after injecting 99mTc through the vein, the liver can be visualized in 3~5min, the liver capsule and intrahepatic bile ducts in 0~15min, the liver and the left and right hepatic ducts disappear in 30min, the gallbladder and common bile ducts are visualized, and most of the radioactive material enters the intestine. Only radionuclides are seen to accumulate in the liver, and the intestine is not visualized suggesting biliary atresia. However, sometimes neonatal hepatitis is also accompanied by biliary obstruction, so the clinical application is limited. 5, MRCP (magnetic resonance biliary system water imaging): MRCP has been widely used in the diagnosis of biliary atresia, the method has high resolution and is increasingly used. In infants with hepatitis, intrahepatic bile ducts, right and left hepatic ducts, common hepatic ducts, and common bile ducts can be seen. 90% of the affected children have gallbladders in the normal size range, and these biliary structures show high signals. In case of biliary atresia, the extrahepatic bile ducts are not visualized and even the gallbladder is not shown, but due to the limited resolution of MRI, its possible that a certain false positive rate occurs. 6, intraoperative cholangiography: intraoperative exploration and intraoperative perforation of the gallbladder for imaging can finally confirm the diagnosis, and laparoscopic cholangiography has been widely accepted because it is a little less invasive and has a faster recovery.