The causes of stones in the common bile duct after cholecystectomy are considered to be related to factors such as gallbladder stones falling out and stones in the common bile duct itself, and the details are analyzed as follows: 1. Fallen gallbladder stones: If the stones in the gallbladder fall into the common bile duct after the surgery due to various reasons, the stones will be found in the common bile duct. In addition, some patients may have gallbladder stones drained into the common bile duct before cholecystectomy. However, the stones are not detected because they are relatively small. It is only after the surgery, as the stones slowly increase in size, that the common bile duct stones are detected by MRI, biliary imaging or CT. 2. There are stones in the common bile duct itself: When the stones are small and there are no symptoms of obstruction, the symptoms are usually not obvious or no symptoms, so it is not easy to be detected. With the further development of the disease, the stones gradually increase in size, and only after the appearance of related symptoms, the choledochal stones are found.