We hope to better define the association between opiate use and biliary dilation, which was evident in our previous retrospective study. This prospective study including all endoscopic ultrasound procedures performed for further evaluation of biliary dilatation in the setting of bilirubin <2 mg/dL will enable accurate measurement of common bile duct and pancreatic duct diameter using endoscopic ultrasound and identification of other non- obstructive factors which may modulate biliary dilation (i.e. age, cholecystectomy status, duration and type of opiate used).

We hope to better define the association between opiate use and biliary dilation, which was evident in our previous retrospective study. This prospective study including all endoscopic ultrasound procedures performed for further evaluation of biliary dilatation in the setting of bilirubin <2 mg/dL will enable accurate measurement of common bile duct and pancreatic duct diameter using endoscopic ultrasound and identification of other non- obstructive factors which may modulate biliary dilation (i.e. age, cholecystectomy status, duration and type of opiate used).

We believe this work will be of great interest to gastroenterologists, as it provides additional data for interpretation of isolated common bile duct dilation in asymptomatic patients.

Inclusion Criteria:

1. Referral/consultation for consideration for EUS ± ERCP
2. Age 18 and older
3. Evidence of biliary dilation on abdominal imaging without obstructive pattern on liver function tests or imaging.
4. Willing and able to comply with the study procedures and provide written informed consent to participate in the study.

Exclusion Criteria:

1. Age <18
2. Potentially vulnerable subjects including, homeless people, pregnant females, employees and students.
3. Participation in another investigational study that may directly or indirectly affect the results of this study within 30 days prior to the initial visit
4. Other biliary process which accounts for patient's abnormal liver function studies/imaging (i.e. mass, stone, cirrhosis).

Patients referred for endoscopic ultrasound (EUS) or endoscopic retrograde cholangiopancreatography (ERCP) for further evaluation of abnormal imaging findings will be screened for inclusion in this study. Patients with biliary dilatation who meet all the inclusion criteria and have none of the exclusion criteria will be invited to participate in this prospective study during their initial clinic visit or hospital consultation.