HEPATIC VEINS x PORTAL VEINS🔶
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Portal vein is formed by the confluence of superior mesenteric and splenic veins, carrying poorly oxigenated blood from GI tract and spleen to the liver. Supplies about 80% of the hepatic flow and 50% of its oxygen supply!
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The portal branches radiate from the porta hepatis, where the main portal vein enters the liver and divides itself into left and right portal veins, which run in a horizontal plane dividing liver sections in superior and inferior segments!
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Hepatic veins are usually three, draining blood to the inferior vena cava! They divide the liver into 4⃣ functional sections! The right hepatic vein (RHV) divides the right hemiliver into an anterior and posterior section! The middle hepatic vein (MHV) is the landmark to the division between the right and left hemiliver. The left hepatic vein (LHV) divides the left hemiliver into medial and lateral segments!.
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The main sonographic features that differentiates hepatic veins from portal veins are:
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1️⃣ORIENTATION: hepatic veins are vertically oriented whereas portal veins are more horizontally oriented!
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2️⃣ECHOGENICITY: remember that portal branches are within the portal triad with the bile ducts and hep. artery branches! This triad is surrounded by a periportal fibrofatty tissue, which produces brighter echoes around the portal veins in comparison with the hepatic veins!
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3️⃣LOCATION: the portal branches run through the middle of the liver segments, that’s why they are called INTRASEGMENTAL vessels! The only exception is the umbilical segment of the left portal vein, which runs between and separates the left medial and lateral sections! On the other hand, hepatic veins are a landmark separating the liver segments, what we call INTERSEGMENTAL vessels!
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4⃣FLOW: In normal conditions, portal veins carry blood TOWARDS 
the liver! This is called a hepatopetal 
flow! Hepatic veins drain liver blood into the inferior vena cava, AWAY:arrow_down: from the liver! This is called hepatofugal 
flow!