Intrahepatic Bile Duct Anatomy: Assessment by CT

Lee, Hong Gi; Kim, Han Joon; Lee, Kwang Soo

Abstract

BACKGROUND: Knowledge of bile duct anatomy is largely obtained through cholangiography. However, it is sometimes difficult to follow the intrahepatic segmental bile ducts and to define the extent of pathology precisely. Basically, the images on cholangiography are projected ones, so they do not provide the spatial concept. In contrast, sequential slices of CT contain information on the threedimensional structure. Purpose : We aimed to assess the intrahepatic bile duct anatomy by examining the CT.
METHODS
The spiral CT images of 42 patients with bile duct dilatation were examined serially from above downward. Intrahepatic bile ducts were followed up to the third-order branches, classified according to the level of branching and compared with those on cholangiography. Further, the relationship between the segmental bile ducts and portal veins were evaluated.
RESULTS
At or below the level of convergence of the ventral(V) and dorsal(D) branches of VIII segment, the posterior bile duct(Bp) arises from right or common hepatic duct(VDP, or VD-P). Below this level, the Bp descends more than 8mm and branches into VI segmental branch(B6) and the posterior trunk(Pr), or it branches directly into B6 and Pr without definite descending portion(Pd). VDP-Pd- Pr,B6(high level of branching of Bp with Pd) was observed in 22, VDP-Pr,B6(high level of branching of Bp without Pd) in 3, VD-P-Pd-Pr,B6(low level of branching of Bp with Pd) in 12, and VD-P-Pr,B6(low level of branching of Bp without Pd) in 4. These findings were closely correlated with those on cholangiography. Regarding the relationship of the segmental bile ducts and portal veins(PV), all right anterior bile ducts were located superior-medial to the PV, and the trunk of right posterior bile duct(Pr) ran superior-lateral to PV in 38 and superior-medial in 4 patients. Most segmental branches of VI and VII segments ran anterior-lateral-superior to PV(VI:39/40, VII:17/18). The Bp coursed above(and behind) the right anterior portal vein(APV) in 39, and below(and in front of) the APV in 3, of which 2 cases had separate and low origin of Bp from common hepatic duct.
CONCLUSION
CT was useful to understand intrahepatic bile duct anatomy.