The purpose of this study is to document that pre-treatment with GN is effective in preventing post-ERCP pancreatitis. In two earlier GN studies, sample sizes were relatively small (less than one hundred) and the rates of post-ERCP pancreatitis in the control group were quite high (15-17%). Therefore, further studies are needed to confirm the promising effect of GN in the prophylaxis of post-ERCP pancreatitis.