PORTAL VEIN

• Normal stent should have detectable flow throughout the lumen. 

• Stent decompresses the portal system directly into the low-pressure hepatic venous system

  • Following stent placement, portal flow in the R and L PVs usually reverses and is directed into stent rather than liver.

  • Flow velocities: 90 - 190 cm/s

• Common problems: stenoses of the stent and of the hepatic vein.

• Signs of stent stenosis:

  • Elevated maximum stent velocity >190cm/s

  • Depressed minimum stent velocity <90cm/s

  • Low PV velocity <30cm/s

  • Temporal increase/decrease in max/min stent velocities on sequential exams

  • Reversal of flow in draining hepatic veins

  • Conversion of L and/or R PV flow from normal pattern towards stent to pattern of flow away from stent on sequential exams is a late manifestation of shunt dysfunction.

• Multiple abnormal parameters makes a stenosis likely and intervention should be considered.