The liver gets around 25% of the total cardiac output, via not one, but two sources:
- Arterial supply from the hepatic artery
- Venous supply from the portal vein
The latter drains blood from the gut, pancreas and spleen, and the former sends a whole chunk of the the blood from anywhere heading towards the liver.
The same factor is believed to be equally important in understanding why the lungs and brain are frequently afflicted by metastasis. Obviously, what makes a site ripe for metastasis isn't only the percentage of the cardiac output that passes through it, but it is certainly an important factor.