Selective cannulation is considered the most challenging step for most of endoscopic retrograde cholangiopancreatography (ERCP). Wire-guided cannulation is the standard technique for initial cannulation. When meeting difficulty, double wire technique (DWT) is widely used. With one guidewire occupying pancreatic duct(PD) , the following cannulation of CBD with a sphincterome preloaded with another guidewire often becomes feasible.

When performing DWT, a sphincterotome should enter the common duct of papilla through a small orifice and be placed in the left and upper direction of PD guidewire. Then another guidewire can be advanced into bile duct. As an advanced cannulation technique, DWT can be successfully performed in up to 80% of difficult patients. However, it can be technically difficult, especially for trainees or endoscopists without adequate experience.

Here we planned to prospectively record the procedures of double-wire cannulation by two trainees without prior experience of DWT. This study aims to delinate the learning curve of DWT and its safety by trainees.

Inclusion Criteria:

• Patients aged 18-90 with native papilla
• patients with diffcult cannulation of bile duct
• Inadvertent pancreatic duct cannulation

Exclusion Criteria:

• Contraindications of ERCP
• Major or minor pancreatic duct as the targeted duct
• Prior EST or needle-knife precut before DWT
• Surgically altered gastrointestinal anatomy
• Papillary carcinoma or stone impaction within papilla
• Complete pancreas divisum
• Pregnant or breastfeeding women
• Unwilling or inability to provide consent