How are the hepatic veins formed?
The outflow system originates at the microscopic level within the hepatic lobule (lobulus hepaticus):
- Within the lobule, arterial and venous blood mix in sinusoidal vessels (vasa sinusoidea) located between the hepatic plates.
- The sinusoids drain into the central vein (v. centralis).
- Leaving the lobule, the central vein continues as the sublobular vein (v. sublobularis).
- Sublobular veins merge into larger collecting veins.
- From the collecting veins, 3–4 large trunks of the hepatic veins (vv. hepaticae) are formed.
Main trunks
The number of hepatic veins can vary, but most frequently three permanent major trunks are distinguished:
- Right hepatic vein (v. hepatica dextra) — from the right lobe of the liver.
- Intermediate hepatic vein (v. hepatica intermedia) — from the quadrate and caudate lobes.
- Left hepatic vein (v. hepatica sinistra) — from the left lobe. Before draining, it connects with the ligamentum venosum (lig. venosum).
Topography and drainage site
The hepatic veins emerge from the liver parenchyma along its posterior margin, in the region of the sulcus for the inferior vena cava.
They empty into the inferior vena cava (v. cava inferior) immediately below the opening in the tendinous center of the diaphragm, before the inferior vena cava enters the right atrium. The hepatic veins are the final tributaries of the inferior vena cava within the abdominal cavity.
The segment where the inferior vena cava passes through the liver and where the hepatic veins enter it is called the second (caval) hilum of the liver.
Clinical significance
- Liver surgery: The liver parenchyma is fragile and tears easily, but the vascular sheaths, especially of the portal and hepatic veins, hold sutures well. The strength of the connective tissue sheaths allows the vessels to be ligated during surgeries.
- Risk of injury: At the site where the hepatic veins enter, the inferior vena cava forms an ampullary dilation. This presents a risk of injury during mobilization.
- Oncology: In hepatocellular carcinoma, invasion of the major hepatic vessels is a worsening factor that advances the disease to an advanced stage (BCLC C).
Fetal characteristics
During the prenatal period, part of the blood passes through the portal vein of the liver and the venous capillaries of the liver. This blood collects in the hepatic veins (vv. hepaticae), which empty into the inferior vena cava.
Class and exam questions
Where do the hepatic veins drain?
They empty into the inferior vena cava (v. cava inferior) upon exiting the liver parenchyma, immediately below the opening in the tendinous center of the diaphragm. These are the final tributaries of the inferior vena cava in the abdominal cavity.
What is the "second hilum of the liver"?
This is the so-called caval hilum — the area where the inferior vena cava passes through the liver and where the hepatic veins drain into it.
Why are sutures placed on vessels rather than liver tissue during surgery?
The liver parenchyma is fragile and tears. Vascular sheaths, especially of the portal and hepatic veins, hold sutures.
What else to study on this topic
- Inferior vena cava (v. cava inferior)
- Portal vein of liver (v. portae hepatis)
- Hepatic lobule (lobulus hepaticus)
- Fetal circulation
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