Third inflow

Third inflow refers to anatomical variants leading to an additional venous inflow to the liver apart from the usual dual blood supply (portal vein and hepatic artery). They tend to be associated with parenchymal pseudolesions (focal hyperenhancement on post-contrast imaging, focal fat infiltration, or focal fat sparing) and, therefore, the recognition of these variant liver hemodynamics is crucial. Potential anatomic variations include:

• aberrant right gastric venous drainage
  • reported prevalence is up to 49% of the population
  • can lead to hepatic pseudolesions in the posterior segment 4
• epigastric-paraumbilical veins
  • venous blood flow from the abdominal wall to the liver
    • superior and inferior veins of Sappey
    • vein of Burow
  • hepatic pseudolesions near the falciform ligament 
• cholecystic veins
  • can lead to hepatic pseudolesions in the posterior segment 4 and 5 
• aberrant left gastric venous drainage
  • around 4% of the population
  • can lead to hepatic pseudolesions in the posterior segment 2 and 3 

NB: the hepatic segments were originally numbered by Roman numerals I to VIII, but the Arabic numerals 1 to 8 are now preferred