Figure 13a. Subtle Klatskin tumor. (a) Subcostal oblique US scan shows a small segment of dilated right hepatic duct (r) with an adjacent, extremely subtle isoechoic mass (m). The mass is further suggested by compression and bowing of the portal vein (PV) and by the separation of the biliary stent (two echogenic lines) from the anterior edge of the portal vein. (b) Subcostal US scan obtained with slight angulation of the transducer provides optimal visualization of the mass (m), which has slightly increased echogenicity and a hypoechoic rim (arrows). PV = portal vein, r = right hepatic duct.