1. Background

   • Advanced guidewires with a U-shaped tip could effectively cross the long or multi-occlusive segment smoothly and go into the distal outflow vessel.
   • The guidewire looping technique is a safe and effective method for the recanalization of the occluded lesions in infrapopliteal vessels.

2. Objective - To compare the performance a loop-tipped guidewire with a straight-tipped guidewire in achieving successful deep biliary cannulation.

3. Design

   - Prospective randomized trial.

4. Setting:

   - Tertiary-care medical center

5. Patients

   - This study will involve 192 patients with biliary diseases which require endoscopic retrograde cholangiopancreatography.

6. Intervention - Cannulation of bile duct by using a loop-tipped guidewire or a straight-tipped guidewire

7. Main outcome measurements - Compare the cannulation success rate, the duration of the cannulation, immediate and late complications.

Inclusion Criteria:

• age > 19 and ability to consent
• no evidence of significant cardiopulmonary or medical comorbidities precluding participation

Exclusion Criteria:

• Known gastroduodenal anatomic abnormalities
• Coagulation disorders (international normalized ratio > 1.5 or platelet count < 50000 cells/cubic millimeter)
• Prior gastric surgery,endoscopic retrograde cholangiopancreatography
• Pregnancy