Access to the main bile duct is the first step in order to perform a therapeutic maneuver for biliary diseases. Early precut has been shown to ameliorate cannulation success rate, specially in difficult cannulation cases, when compared to guidewire cannulation (which is considered, for most, the standard technique). We aim to perform a randomized clinical trial comparing fistulotomy (F) precut vs guidewire cannulation (CC), as a primary cannulation technique, and compare outcomes between high experienced endoscopists (> 200 ERCPs[Endoscopic Retrograde cholangiopancreatography]) and low experienced endoscopists (< 200 ERCPs).

Endoscopic Retrograde Pancreatography Cholangiography (ERCP) is the standard procedure for the treatment of pathologies that affect the bile duct. Approaching to the ampulla followed by deep selective biliary cannulation is the first step in order to apply any therapeutic method for bile duct pathologies. In patients with a normal anatomy it is estimated that about 11% of therapeutic ERCPs will be considered difficult biliary cannulation (duration of cannulation> 5 minutes, more than 5 attempts, > 1 cannulation of the main pancreatic duct). When early conventional precut has been compared to guidewire cannulation, cannulation success is in favor of precut with 86.7% compared to 66.7%; with a lower post-ERCP acute pancreatitis event rate: 6.1% vs 9.1%.

Objective: To determine the rate of biliary cannulation by comparing two techniques (fistulotomy versus standard biliary cannulation technique with guidewire) according to the endoscopist experience in ERCP.

Material and methods: A randomized prospective clinical trial will be conducted in the gastrointestinal endoscopy department of the CMN SXXI specialties hospital between the period of August 2019 and March 2020. 2 groups will be assigned as following: in group A the primary approach to access the bile duct will be conventional cannulation (CC) with guidewire, and group B for fistulotomy (F). On the other hand, there will be 2 groups of endoscopists (high experience> 200 ERCP) [HE] and low experience (<200 ERCP) [LE]. In total 4 groups: CCHE, CCLE, FHE, FLE. All patients undergoing ERCP with suspected or confirmed of choledocholithiasis, malignant and benign stenosis of the bile duct, men and women between 18 and 90 years will be included. Exclusion criteria: patients with previous ERCP, gastro-duodenal anatomy altered by previous surgery, suspicion or diagnosis of ampullary neoplasm, duodenal cancer, periampullar diverticula types 1 and 2, pregnant women, coagulopathy with INR greater than 1.5. Elimination criteria: patients with incomplete ERCP due to adverse anesthesia events. The reason and indication of the ERCP study will be determined, a data collection sheet will be used compiling: clinical data such as age, sex, concomitant diseases, symptoms, biochemical data, imaging studies (abdominal ultrasound, abdominal CT and MRCP), findings on ERCP (characteristics of the papilla, presence of periampullar diverticula); details of the cannulation technique such as the number of attempts, time to access the bile duct. A comparison will be made between both techniques and both groups HE and LE. The success rate of biliary cannulation and complication for both groups of doctors and maneuvers used will be documented.

Statistical analysis: Continuous variables will be described with mean, median or standard deviation according to their distribution; and categorical variables will be described as percentages. Categorical variables will be compared using Chi-square or Fisher's exact test, while quantitative variables will be compared using T-Student or Mann Whitney U test. A P less than 0.05 will be considered statistically significant (for T-Student and Mann-Whitney U will be 2-tailed). A sample size of 80 patients for each group was calculated.

Inclusion Criteria:

• All patients undergoing ERCP with suspected or confirmed of choledocholithiasis, malignant and benign biliary stenosis.

Exclusion Criteria:

• patients with previous ERCP, altered gastro-duodenal anatomy by previous surgery, suspicion or diagnosis of ampullary neoplasm, duodenal cancer, periampullary diverticula types 1 and 2, pregnant women, coagulopathy with INR greater than 1.5.

Elimination Criteria:

- Incomplete procedure due to anesthesia adverse events.

The participant will be allocated to one group of the intervention conventional guidewire biliary cannulation or fistulotomy based on program software