 Post-endoscopic retrograde cholangiopancreatography ERCP pancreatitis PEP has been a well-recognized complication with significant morbidity and even mortality. A variety of possible mechanisms has been suggested in the occurrence of pancreatitis, but papillary edema caused by manipulations during cannulation or endoscopic treatment has received the most attention. The papillary edema may cause temporary outflow obstruction of pancreatic juice, and then increase ductal pressure, resulting in the occurrence of pancreatitis. Topical application of epinephrine on the papilla may reduce papillary edema. Moreover, it is reported that epinephrine sprayed on the papilla may be effective to prevent PEP. However, it is still unclear that epinephrine sprayed on the papilla can prevent acute pancreatitis after endoscopic retrograde cholangiopancreatography. We therefore designed a prospective randomized trial to determine whether epinephrine sprayed on the papilla prevent PEP after ERCP. 