<qa>  What is the name of the study that was conducted using large-balloon dilation afterEndoscopic retrograde cholangiopancreatography ERCP has become one of the most important techniques in the treatment of bile duct stones. A number of studies have been conducted using large-balloon dilation LBD after adequate EST to extract large bile duct stones. In those studies, the authors suggested that EST plus LBD might lower the risk of post procedure pancreatitis PEP by directing balloon dilation toward the bile duct rather than the pancreatic duct. It has been reported that EPBD followed by insertion of nasobiliary drainage catheter can prevent PEP. However, it is still unclear that nasobiliary drainage after endoscopic sphincterotomy plus large-balloon dilation for preventing postoperative pancreatitis in treating of large bile duct stones.The investigators therefore designed a prospective randomized trial to determine whether nasobiliary drainage prevent PEP after endoscopic sphincterotomy plus LBD for the treatment of large bile duct stones. 