Needle Knife Fistulotomy Versus Partial Ampullary Endoscopic Mucosal Resection for Difficult Biliary Cannulation

Inclusion Criteria: * Patient who submitted a written informed consent for this trial, and aged between 18-90 years old * Patient who have naïve papilla (no previous procedure was performed at ampulla) * Patient who is suspected to have a biliary obstruction or biliary disease * Patient who is needed to have endoscopic retrograde cholangiopancreatography for treatment of biliary obstruction * Patient who have risks of post-endoscopic retrograde cholangiopancreatography p Exclusion Criteria: * Patient who is pregnant * Patient with mental retardation * Patient allergic to contrast agents * Patient who received sphincterotomy or pancreatobiliary operation previously * Patient who have ampulla of Vater cancer * Patient who have difficulty for the approach to ampulla due to abdominal surgery including stomach cancer with Billroth II anastomosis * Patient who have pancreatic diseases as bellow (at least one more); * acute pancreatitis within 30days before enrollment * idiopathic acute recurrent pancreatitis * pancreas divisum * obstructive chronic pancreatitis * pancreatic cancer * Patients with Type-1, non-protruding Type-2 and Type-4 papilla