Stones in the bile ducts can usually be detected by ultrasound, but if there is gas interference due to intestinal distension, some of the bile ducts may not show up clearly. If you want to check the condition of the bile ducts, the best choice is magnetic resonance of the liver and gallbladder plus MRCP, which can visualize the whole bile ducts very clearly, and some abnormalities can basically be detected, with better accuracy and sensitivity than ultrasound. If you want to have an ultrasound, you must have an empty stomach on the morning of the second day, and the clarity and accuracy of the examination should be high, so as not to show poorly due to gas interference. For bile duct examinations, supplemental MRI and MRCP examinations may be required.