Portal Hypertension in Children: Ultrasound and Doppler Signs and Blood Flow Direction
Blood Flow Direction in the Portal Vein
The primary Doppler criterion for portal hypertension is a change in blood flow direction in the portal vein. On spectral Doppler ultrasound examination of the liver, retrograde (hepatofugal) blood flow in the portal vein is identified. On color Doppler mapping, such flow is displayed in blue, and on the spectral waveform is located below the baseline. Color Doppler is used to assess blood flow direction in vascular structures, while spectral Doppler demonstrates abnormal patterns of the portal and hepatic veins.
Portosystemic Collaterals
Portal hypertension results in the formation of collateral circulation. One of the characteristic signs is the recanalized paraumbilical vein, originating from the left branch of the portal vein and extending anteriorly along the falciform ligament toward the inferior epigastric vein. The umbilical vein may recanalize secondarily in the setting of portal hypertension.
This vessel is best visualized in the longitudinal plane near the midline as a tubular structure passing posterior to the medial surface of the left hepatic lobe. At the hepatic hilum, the portal vein may appear as a worm-like structure completely filled with color, reflecting periportal collateral circulation.
Assessment of Liver and Spleen Stiffness
In children, ultrasound elastography is applied to assess hepatic fibrosis. Noninvasive diagnosis of idiopathic portal hypertension may be based on measurement of liver and spleen stiffness using ARFI elastography. Specific threshold values for the pediatric population are not provided in the supplied materials — [to be clarified].
Frequently asked questions
What is the primary Doppler sign of portal hypertension?
Retrograde (hepatofugal) blood flow in the portal vein: blue on color Doppler and below the baseline on spectral analysis.
How do you differentiate blood flow direction — using color or spectral Doppler?
Color Doppler is used to assess blood flow direction in vessels, while spectral Doppler is used to identify abnormal patterns of the portal and hepatic veins.
Which collateral is most characteristic?
The recanalized paraumbilical vein originating from the left branch of the portal vein, extending anteriorly along the falciform ligament toward the inferior epigastric vein.
Where is the recanalized umbilical vein best visualized?
In the longitudinal plane near the midline as a tubular structure posterior to the medial surface of the left hepatic lobe.
Is elastography applicable in children with portal hypertension?
Yes, elastography is used to assess hepatic fibrosis in children; in idiopathic portal hypertension, liver and spleen stiffness are measured using ARFI elastography. Pediatric threshold values — [to be clarified].