Our aim is to compare the efficacy, safety, procedural time required, and costs of a strategy initially employing cholangioscopy guided intraductal lithotripsy (laser/electrohydraulic lithtripsy (EHL)) versus a strategy initially using papillary dilation for removal of large bile duct stones.

The study will be a prospective single blind randomized comparative trial. All patients presenting with choledocholithiasis will be considered for the study. If their ultrasound, computed tomography, or magnetic resonance imaging demonstrates a large stone (>1cm) and they do not fulfill the exclusion criterion they will be eligible for the study. If a prior Endoscopic retrograde cholangiopancreatography (ERCP) demonstrates a stone >1cm, which could not be removed with standard methods, they will also be eligible. Randomization will be stratified based on whether or not the procedure is a first or repeat ERCP

Patients will be randomized using a computer generated randomization schedule with concealed allocation in a 1:1 assignment (allocation ratio) to initial cholangioscopy guided lithoripsy versus initial papillary dilation. Randomization will be blocked in groups of 12.

In those randomized to cholangioscopy-guided lithotripsy, the procedure will be performed in the standard manner using a single operator cholangioscopy system and a holmium laser or EHL (dependent on availability). Those in the papillary dilation arm will undergo the standard approach using the combined papillary dilation balloon sphincterotomy system. The patients will be blinded as to treatment arm.

"Conventional" methods including mechanical lithotripsy or stent placement may be used to remove stones/debris in combination with the specified intervention, as is done for standard clinical care. Use of these strategies will be recorded

If stone removal fails with the assigned strategy, this will be considered failure of the assigned intervention. This decision will be made by the attending endoscopist and recorded. The patient will then crossover into the other treatment arm.

The primary outcome will be complete stone clearance in the first study procedure by the assigned method. Additional outcomes will be total procedure time, cost of equipment, and number and type of complications. Additional ERCP may be needed for complete removal in some cases (i.e. complete removal in first attempt is not possible), thus we will also compare the number of ERCP needed for final stone clearance and whether stone removal is eventually achieved by endoscopic methods (comparison will be on an intention to treat basis). Additionally, if patients require surgical stone removal for the standard clinical indication in the case that endoscopic strategies are not successful, this will be recorded.

The patients will be followed clinically by the principal investigator assisted by a research coordinator on days 1,7 and 30 post procedures. This will be done as a brief follow up visit if the patient is still hospitalized or by telephone call thereafter.

Thus, all procedures performed in this study represent standard clinical care, which would be used even if the patients did not take part in the study, except that the initial choice to use cholangioscopy guided lithotripsy versus papillary dilation will be randomized.

Inclusion Criteria:

• Patients 18 years and older
• Undergoing ERCP at LAC+Medical Center or Keck Hospital of USC for the standard indication of bile duct stones with evidence of a large stone (>1cm) demonstrated either on Ultrasound, computed tomography, prior ERCP, or magnetic resonance imaging.

Exclusion Criteria:

• Patients Under the age of 18
• Patients with biliary malignancy
• Prior biliary diversion surgery
• Prior gastric bypass surgery
• Patients who are incarcerated
• Patients who are unable to give consent
• Patients who pregnant

Participants in the study will be blinded to treatment arm. Care providers and Investigators will be unblinded to treated arm.