Liver Sonography by Duplex and Color Doppler

Upon entering the liver, both the hepatic artery and the portal vein branch into smaller vessels that eventually become capillaries. As the blood begins to exit the liver, these capillaries become venules and eventually form the hepatic veins that enter the inferior vena cava with blood flow back to the heart. In most circumstances, there are three main hepatic veins, the left, middle and right.

Liver Doppler Technique

Liver Doppler should be performed using a sector or curved array transducer with a frequency raging between 2 to 6 MHz, depending on the patient’s body habitus. The scan should also be performed after an overnight fast to limit the amount of bowel gas in the region of the porta hepatis. When evaluating the portal venous system, the main portal vein as well as the right and left portal veins and their respective branches should be evaluated for patency and flow direction. The right and main portal veins are imaged best through an intercostal approach with the patient turned slightly to the left. The transducer should be angled obliquely and placed slightly laterally along the axis of a lower rib. An attempt should also be made to visualize the right and main portal veins from a subcostal approach, but frequently, this approach cannot be used due to overlying bowel gas. Because the left portal vein runs in an anterior direction, it is best visualized with the patient supine and with deep inspiration. The probe should be oriented in a parasagittal plane in the sub-xiphoid region.