Figure 7b. Neural plexus invasion by cancer of the lower bile duct. Postcontrast CT scans show a tumor (* in a) of the lower bile duct. Neural plexus invasion is seen as extension of the mass through the root of the SBM and along the inferior pancreaticoduodenal artery and first jejunal artery (arrows in b) to the right aspect of the SMA (arrowheads in a). D = duodenum, P = pancreatic head, V = SMV.