Cholangioscopy, or direct visualization of the bile ducts was first documented in the late 1970s and has made many advances over the last few decades. The advent of mother-baby scopes allowed for both diagnostic and therapeutic procedures, though the early scopes were often fragile, and cumbersome due to the need for two endoscopists. Ultraslim endoscopes later became popular as a method to digitally view the bile ducts, however, often needed guide-wire or balloon-assistance to allow for cannulation. Other disadvantages of these systems included limited steerability, and poor irrigation capabilities.

The advent of Spyglass, a single-operator peroral cholangioscopy method allowed for a fiberoptic, catheter-based system that could be easily used for diagnostic and therapeutic purposes in the biliary system. However, image quality was often lacking due to the fiberoptic technology. The new digital Spyglass system rectifies this inadequacy by introducing a digital sensor for better image quality, which will allow for better visualization and diagnosis of indeterminate strictures. Furthermore, modification of the scope platform allows for efficient use, reliable directionality of the scope tip, and improved ease of passage of accessories during therapeutic procedures such clearing stones or stent placement.

All patients referred for the evaluation of indeterminate strictures or removal of difficult stones will be eligible for enrollment in the consortium. The PI or study coordinator will meet with the patient and discuss the study, its objectives, and obligations with each patient. After full disclosure, informed consent will be obtained.

Upon consent, basic demographics and data from prior procedures (when available) will be recorded. An endoscopist proficient in ERCP, with expertise in cholangioscopy, will perform the procedures using the Spyglass DS system with its associated components including biopsy forceps (SpyBiteTM) and other accessories as necessary. Procedure time, visual findings, number of biopsies taken, pathology, stone location, stone size, and method of stone clearance and adverse events will be recorded on data collection forms and transferred into a centralized password protected database. All patients will be followed for 6-12 months or surgery (stricture cohort) to assess accuracy or stone recurrence rates.

Inclusion Criteria:

• All patients referred for the evaluation of indeterminate strictures or removal of difficult stones.

Exclusion Criteria:

• All patients who are unable or unwilling to give consent will not be included in this study

Formation of a multi-site prospective database of all patients referred for the evaluation of indeterminate strictures or removal of difficult stones.