Figure 4. Direct cholangioscopy and intraductal ultrasonography (IDUS) images from left hepatic duct branches to the lower portion of the common bile duct. The images, in which the cholangioscopy and IDUS images are arranged side by side (A, B, E, and F), are images of almost the same bile duct site. Each site of these images is indicated by a yellow line on the endoscopic retrograde cholangiopancreatography (ERCP) image (G), from (A) to (F), from upstream to downstream. The IDUS image at left hepatic duct branches shows no wall thickening (A). The images at the levels of the bifurcation of the right posterior sectoral duct from the left hepatic duct (B and C, yellow arrow), of the bifurcation of the anterior sectoral duct from the common hepatic duct (D, white arrow), and of the lower common bile duct (F, white arrow head shows pancreatic duct) show relatively uniform and diffuse wall thickening continuously, extending beyond the sites of stenosis indicated by ERCP. The IDUS images at the 2 sites of stenosis of the common hepatic duct (E, yellow arrow head shows the right hepatic artery) and of the upper common bile duct show wall thickening higher than that at the other sites, but its outer boundary is almost preserved. Direct cholangioscopic images show whitish smooth surface mucosa not only at the level at which wall thickening is not detected (A), but also at the levels at which wall thickening is detected by IDUS (B and F). At the small parts of the tightest stenoses of the common hepatic duct and the upper common bile duct are shown relatively well-ordered blood vessel distension (E).