title: A study of the accessory hepatic vein to segments VI and VII with a morphological reconsideration of the human liver.
abstract: BACKGROUND
  The liver is supplied by the common hepatic artery from the celiac trunk and by the portal vein from the gastrointestine. This double blood supply to the liver by the hepatic artery and the portal vein produced a complicated structure in the liver. For the blood outflow, we can see right, intermediate and left hepatic veins, and irregular veins: the accessory hepatic veins. These veins drain the blood in the liver into the inferior vena cava. In this study, we studied the layout of the accessory hepatic vein draining segments 6 and 7 in the human livers and attempted to reconsider the structure of the liver by the layout of the accessory hepatic vein.
  
  
  METHODS
  Sixty livers were subjected in this study. They were prepared by using forceps to trace the layout of the blood vessels inside the livers. We carefully examined the relation between the layouts of the accessory vein to the segments 6 and 7 and of the portal vein. The confluence patterns of the accessory hepatic vein into the inferior vena cava were also examined to find the character of the vein. The relation between the accessory hepatic vein and standard hepatic veins was also studied.
  
  
  RESULTS
  We found 2.2 accessory hepatic veins in one liver on average in our study. The vein was always within the area of segments 6 and 7, and did not surpass the boundary. We found at most five accessory hepatic veins in a liver in two cases. The accessory hepatic vein to the segments 6 and 7 always had its stem on the dorsal side to the portal vein. Different from the stem, the periphery of the accessory hepatic vein freely distributed with the peripheral branches of the portal vein. The area distributed by the accessory vein was also always dorsal part within the segments 6 and 7. The vein was small usually, but was big in few cases. When the vein was big, the area became solely drained by the accessory vein, because the standard hepatic veins (right and intermediate hepatic veins) did not reach the area, and we did not find any communication between the accessory vein and the standard veins. As the remaining region in the segments 6 and 7 became smaller, the draining right standard hepatic vein became shorter and smaller.
  
  
  CONCLUSIONS
  The region drained by the accessory hepatic vein excluded the standard hepatic veins. Therefore, there are two different draining venous networks in the area of segments 6 and 7 classified by Couinaud.
  
  
  CONCLUSIONS
  The accessory hepatic vein draining segments 6 and 7 distributed somewhere dorsal side in the segments 6 and 7. The area where the accessory vein distributed was the region where standard hepatic veins did not reach. This would suggest that the region drained by the accessory hepatic vein makes an isolated segment in the liver in the segments 6 and 7 by the Couinaud's Classification. The area might have a unique blood circulation system.
authors.affiliation: Department of Anatomy, Tokyo Medical University, 6-1-1, Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan.
authors.forename: Sichen
authors.initials: S
authors.lastname: Buhe
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Miyaki
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Saito
authors.forename: Alimujiang
authors.initials: A
authors.lastname: Sawuti
authors.forename: Hayato
authors.initials: H
authors.lastname: Terayama
authors.forename: Munekazu
authors.initials: M
authors.lastname: Naito
authors.forename: Shuang-Qin
authors.initials: SQ
authors.lastname: Yi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Itoh
mesh_terms: D002102:Cadaver; D006503:Hepatic Veins / Q000033:anatomy & histology*; D006801:Humans; D008099:Liver / Q000033:anatomy & histology* / Q000098:blood supply*