Page 353 - Libro 2

22
The Hepatoportal System
Wayne C. Leonhardt and Ann Marie Kupinski
OBJECTIVES
KEY TERMS
hepatic artery | hepatic vein | hepatofugal | hepatopetal | portal hypertension | portal vein | TIPS
GLOSSARY
ascites an accumulation of fluid within the peritoneal cavity
Budd-Chiari syndrome hepatic vein thrombosis hepatofugal away from the liver, usually refer-
ring to blood flow away from the liver
Duplex sonography is the most common imaging technique used to evaluate the portal and hepatic venous systems. This important noninvasive tool is paramount in determining the presence of flow, di- rection of flow, blood velocity, and in characterizing flow hemodynamics. A variety of vascular disorders alter blood flow into, within, and out of the liver. Du- plex with color Doppler is particularly useful in the detection of an intraluminal thrombus, a hepatofugal flow, collateral circulation, an arterio-portal fistula, absent flow, and increased or decreased flow in both portal and hepatic venous systems. This chapter will review the sonographic duplex findings and the he- modynamics of the normal hepatoportal system as well as various pathological conditions.
ANATOMY
The liver receives a dual blood supply from the hepatic artery and portal vein. These two vessels constitute the hepatic inflow. The hepatic artery supplies approx- imately 30% of incoming blood. It carries oxygenated blood through branches in the portal triad and enters the sinusoids (capillaries) to reach the central veins
hepatopetal toward the liver, usually referring to the normal direction of portal vein flow
portal hypertension elevated pressure within the portal vein
TIPS transjugular intrahepatic portosystemic shunt
within the liver. The portal vein supplies the remaining 70% of hepatic blood flow.1 It carries nutrient-rich blood from the gastrointestinal tract to the portal triad, where it enters the sinusoids to reach the central veins. Central veins are the actual beginnings of the hepatic venous system. They enter sublobular veins, which unite and converge to form three hepatic veins that drain into the inferior vena cava (IVC). The hepatic veins comprise the primary hepatic outflow vessels.
PORTAL VENOUS SYSTEM
Just slightly to the right of midline, the main portal vein (MPV) begins the junction of the splenic vein (SV) and superior mesenteric vein (SMV). The MPV courses cephalad approaching the porta hepatis and lies anterior to the IVC. The porta hepatis is the trans- verse fissure on the visceral surface of the liver be- tween the caudate and quadrate lobes where the portal vein and hepatic artery enter the liver and the hepatic duct leaves the liver.2 Figure 22-1 illustrates the nor- mal portal venous anatomy and flow direction. Enter- ing the portal hepatis, the MPV divides into a smaller, more anterior, and cranial left portal vein (LPV) and a larger, more posterior, and caudal right portal vein
Identify normal hepatoportal anatomy
Describe normal hepatoportal Doppler waveforms
List the causes of portal hypertension
Describe portosystemic collateral pathways associated with portal hypertension
List sonographic findings associated with portal hypertension
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