Medicine can be learned by example, and many treatments are similar, so there is no harm in learning more skills. Previously, I have been dilating the bile duct with a balloon under ERCP. Suddenly, I met a patient with left external lobe stone residual stone, but the bile duct is narrow, choledochoscope can not pass, the stone can not be removed, I was anxious! Why not dilate the bile duct before removing the stone? There is no precedent in the department, but I heard that other hospitals have done it, so I contacted balloon suppliers extensively, choledochoscopic treatment holes are relatively small, the key is to find one that can pass through the 2L treatment holes, ERCP balloon sphincter tube we are very experienced, they are too thick to use, and the effort is not rewarding, but also finally found an endoluminal dilatation balloon that can pass through the small choledochoscopy holes, and the final surgery was very successful! The patient was very happy when the bile duct was dilated by 7mm and the stone was successfully removed!