The main purpose of the study is to evaluate the prevalence of difficult biliary cannulation using endoscopic retrograde cholangiopancreatography (ERCP) according to the criteria defined by the European Society of Gastrointestinal Endoscopy (ESGE) and the American Society for Gastrointestinal Endoscopy (ASGE), as well as the predictive factors for this event in a prospective, multicenter study. Consecutive patients undergoing ERCP will be included in the study

We will also assess:

Evaluate the failure of biliary cannulation in our setting. Evaluate predictive factors for difficult cannulation and cannulation failure using ESGE criteria.

Design an "a priori" predictive model for difficult cannulation and cannulation failure.

Cost study: record of materials used.

All consecutive patients who meet the inclusion criteria and none of the exclusion criteria will be offered participation in the study. They will be informed by one of the investigators from each center and will sign an informed consent form. A data collection sheet will be completed to record demographic data, the indication for the procedure, and technical variables.

The procedures will be performed by endoscopists with at least 200 ERCPs and more than 5 years of experience. All patients, except in cases of allergy, will receive 1 suppository of indomethacin or diclofenac before the procedure. In cases of allergy, pre-procedure hydration with Ringer's lactate will be administered if there is no contraindication (consider the protocol proposed by the ESGE: 3 mL/kg/hour during ERCP, 20 mL/kg as a bolus after ERCP, and 3 mL/kg/hour for 8 hours post-ERCP). The use of a pancreatic stent should be considered when indicated.

After the procedure, patients will remain hospitalized for at least 24 hours in the hospital. The patient's medical record will be reviewed 7 days after the procedure to check for any adverse effects, and a follow-up phone call will be made to detect any adverse effects.

Initially, a pilot study will be conducted with 600 patients, assessing based on the results-that is, the percentage of patients with difficult cannulation and the number of independent variables associated in the multiple logistic regression-the need to include a larger number of patients. For each variable included in the multiple logistic regression analysis, 8 to 10 cases of patients with difficult cannulation would be required.

Inclusion Criteria:

• Age >18 years
• Signed informed consent
• Patients indicated for ERCP

Exclusion Criteria:

• INR > 1.5
• Platelets < 50,000/mm³
• Patients with a prior endoscopic sphincterotomy
• Papilla of Vater not accessible via duodenoscope (gastric or duodenal stenosis due to neoplasm) or gastric surgery (Billroth II, Roux-en-Y)
• Known pancreas divisum
• Indication due to pancreatic duct pathology

All the consecutive patients with an indication of a endoscopic retrograde cholangiopancreatography meeting inclusion and exclusion criteria will be included