• Percentage of successful selective biliary cannulation
  

• Number of attempts and time of cannulation.
  
• Morbimortality associated in both groups at hospital discharge and 4 weeks after ERCP procedure
  
• Factors associated with successful cannulation for both techniques
  

Complications associated with ERCP have been related with certain characteristics of the procedure. One is the number of attempts of selective biliary cannulation. Our hypothesis is that double guide wire placement could be a useful technique for selective biliary cannulation in those cases of difficult ERCP procedures, reducing the number of cannulation attempts and the complication associated with the procedure.

We are conducting a controlled prospective multicentre randomized study to compare the double guide wire technique with the conventional method in two groups previously randomized after presenting a difficult selective biliary cannulation under the conventional method. The study is carried out in six public Hospitals from Spain. Assignation is concealed to both groups, and the expected study period is 18 months for a number of randomized patients equal or over 262 (statistical power of 90% with an α-error of 0.05, to detect a success rate of 74% in the group undergoing double guide wire technique against a success rate of 60% in the control group). The main outcome variables are successful selective biliary cannulation (primary outcome variable), number of attempts and morbimortality associated in both groups (secondary outcome variables).