Vascular Liver Disease

What vessels supply blood and are responsible for oxygen delivery to the liver ?

The portal vein is responsible for approximately 70% of total liver blood flow and supplies slightly less than half the needed oxygen. Although of lower oxygen content, the portal vein delivers intestinal nutrients, drugs, and inflammatory mediators directly to the liver after intestinal absorption. The hepatic artery (branch of the celiac artery via the hepaticoduodenal artery) accounts for approximately 30% of the hepatic afferent flow but more than 50% of the oxygen. The hepatic artery supplies the majority of oxygen to the biliary tree.

Name the vessels that compose the portal vein .

Venules drain blood from the intestinal and splenic capillaries and form the superior and inferior mesenteric veins and the splenic vein. These veins join to form the portal vein that subsequently divides into tributaries that eventually branch into fenestrated capillaries (sinusoids) of the liver.

How does blood flow occur at the microscopic level in the liver ?

Blood flows down a pressure gradient from the portal venule and hepatic arteriole (derived from the portal vein and hepatic artery, respectively) through sinusoids. Fenestrated endothelial cells line these sinusoids. They supply sheets of hepatocytes before draining into the central venule.

How many anatomic segments compose the liver ?

There are eight segments of the liver defined by their own afferent and efferent blood flow ( Figure 26-1 ).

What is unique about the caudate lobe ?

The caudate lobe is segment one and uniquely drains directly into the inferior vena cava (IVC) through the dorsal hepatic veins (HVs).

Describe the three “ zones ” of the hepatic lobule with respect to blood flow .

The hepatocytes can be defined by their proximity to either the portal triad or central venules. Zone 1 includes hepatocytes surrounding the portal tract. These hepatocytes receive the most oxygenated blood but also are the first exposed to any toxins. Zone 2 includes hepatocytes found in the intermediate area between the periportal and perivenular areas. Zone 3 is made up of perivenular hepatocytes that are the most susceptible to hypoxic mediated injury ( Figure 26-2 ).

What is Budd - Chiari syndrome ( BCS ) and what blood vessels are involved ?

BCS is any pathophysiologic process that results in interruption or decrease of the normal blood flow out of the liver. This commonly involves complete or partial thrombosis of one or all three major HVs (right, middle, and left) or small HVs. In Asia, pure IVC obstruction or combined IVC-HV obstruction is more commonly diagnosed.

What are secondary causes of BCS ?

See Box 26-1 .