Primary Needle Knife Fistulotomy Versus Conventional Cannulation Method

Inclusion Criteria: * Patient who submitted a written informed consent for the this trial, and 18 \~ 90 years old * Patient who have naïve ampulla (no previous procedure was performed at ampulla) * Patient who is suspected to have 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 pancreatitis among bellows (at least one more); 1. suspected biliary sphincter of Oddi dysfunction 2. young age (18\~50 years) 3. female 4. normal common bile duct diameter (≤9mm) 5. normal serum bilirubin level 6. Obesity (body mass index \> 30) 7. Past history of acute pancreatitis Exclusion Criteria: * Patient who is below 18 year old * Patient who is pregnant * Patient with mental retardation * Patient is sensitive to contrast agents * Patient who received sphincterotomy or pancreatobiliary operation previously * Patient who have ampulla of Vater cancer * Patient who have difficulty for 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); 1. Patient who have acute pancreatitis within 30days before enrollment 2. Patient who have idiopathic acute recurrent pancreatitis 3. Patient who have pancreatic divisum 4. Patient who have obstructive chronic pancreatitis 5. Patient who pancreatic cancer * Patients who have improper ampulla shape as bellows; 1. Small ampulla (ampulla without oral protrusion) 2. Flat or crooked or asymmetric ampulla 3. Ampulla with peri-ampullary diverticulum type I or II