Portal vein

Dr Henry Knipe and Dr Jeremy Jones et al.

Portal vein (PV) (sometimes referred to as the main or hepatic portal vein) is the main vessel in the portal venous system and drains blood from the gastrointestinal tract and spleen to the liver.

The portal vein, usually measures approximately 8 cm in adults. It originates behind the neck of the pancreas and is classically formed by the confluence of the superior mesenteric and splenic veins, and also receives blood from the inferior mesenteric, gastric, and cystic veins.

Immediately before reaching the liver, the portal vein divides into left portal vein (supplying liver segments II, III, IV) and the right portal vein, which subsequently divides further into anterior (supplying liver segments V and VIII) and posterior (supplying liver segments VI and VII) portal veins.

It ramifies further, forming smaller venous branches and ultimately portal venules. Each portal venule courses alongside a hepatic arteriole and the two vessels forming the vascular components of the portal triad. These vessels ultimately empty into the hepatic sinusoids to supply blood to the liver.

75% of the blood supplied to the liver comes from the portal vein, but it only supplies 50% of the oxygen supply to the liver.

The overall incidence of portal vein variation is reported to be ~25% (range 20-30%), which should be recognised prior to procedures such as liver transplantation, complex hepatectomy and portal vein embolisation 2-4

  • portal vein trifurcation (most common)
    • portal vein divides into three branches: left portal vein, right anterior portal vein, and right posterior portal vein
  • right posterior portal vein splits off as the first branch of the portal vein; the right anterior and the left portal veins then originate from a common trunk
  • portal vein duplication (rare)
  • portal vein absence (rare)

There is an increased risk of bile duct hilar anatomical variation in the presence of portal vein variants.


Abdominal and pelvic anatomy
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Article Information

rID: 5732
Section: Anatomy
Tags: rewrite, refs
Synonyms or Alternate Spellings:
  • Portal vein (PV)
  • Main portal vein (MPV)

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    Figure 1: portal vein
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    Figure 2: portal vein cross-section image
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    Figure 3: pancreas and duodenum in relation to PV
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    Figure 4: CTA portal vein anatomy
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