Variation in portal and hepatic venous anatomy as shown by magnetic resonance imaging: implication for transjugular intrahepatic portosystemic shunt.

Magnetic resonance imaging (MRI) is able to show the portal and hepatic venous anatomy. Variation in the relative position of the right portal vein and the right hepatic vein is shown in three parasagittal planes in three different cases and accounts for the different appearances of the transjugular intrahepatic portosystemic shunt (TIPS) in three patients. MRI shows that the optimal plane of exit from the right portal vein is 1-2.5 cm from the lateral wall of the inferior vena cava but individual variation does occur: a right portal vein with a more anterior and craniad location may not be accessible to the Colapinto needle; a parenchymal tract which is directed too far inferomedially risks puncturing the portal vein outside the liver capsule.