Normal bile duct findings using peroral cholangioscopy-guided probe-based confocal laser endomicroscopy (with video).

We encountered a case of wall thickening of the bile duct in a 69-year-old man. endoscopic retrograde cholangiopancreatography (ERCP) was performed for detailed examination. When an area considered to be the healthy bile duct was examined by peroral cholangioscopes (POCS) (SPYGlass DS), the vascular network was observed. POCS-guided, probe-based confocal laser endomicroscopy (pCLE; CholangioFlex, Cellvizio; Mauna Kea Technologies, Paris, France), performed using the fluorescein-dripping method on this area, showed a reticular network of thin dark branching bands, which were presumed to be a collagen bundle or lymphatic vessels according to the Miami Classification. However, 8 μm-diameter objects thought to be red blood cells were observed inside the bands, which were considered to correspond to the vascular network observed on POCS. A biopsy specimen of this site was taken. The histological examination demonstrated capillaries just beneath the bile duct epithelium. Thus, the histology also suggested the presence of the vascular network. In this study, we obtained findings that cannot be explained in terms of the Miami Classification, which we describe here with a video.