Fluid helps some patients and harms others. Venous congestion, where pressure backs up from the right heart into the organs, is one sign that more fluid will harm. The portal vein shows this pressure because the liver sits between it and the heart.
Scan images in the graphic are illustrations, not patient scans.
The scan
- Use the curvilinear probe, abdominal preset.
- Find the portal vein at the liver hilum, from below the right costal margin or through the right intercostal spaces. It runs towards the liver with bright walls.
- Confirm flow with colour Doppler.
- Place the pulsed-wave Doppler gate inside the portal vein, with the beam as parallel to the flow as you can get it.
- Record several seconds, and save the trace.
Reading the trace
- Normal. Continuous flow towards the liver, with little variation.
- Mild pulsatility. Regular undulations in velocity with each heartbeat.
- Marked pulsatility. Large swings in velocity, often reaching or crossing the baseline, so flow briefly stops or reverses.
Pulsatility fraction = (maximum velocity minus minimum velocity) divided by maximum velocity. Under 30% is normal. 30% to 50% is mildly abnormal. 50% or more is severely abnormal.
Other causes of a pulsatile portal vein
Healthy, thin young adults sometimes show a pulsatile portal vein. Tricuspid regurgitation and arteriovenous shunts in the liver also cause it. Cirrhosis stiffens the liver and damps the signal, so congestion is harder to see.