Change of orientation of the porta hepatis and portal vein in liver atrophy and hypertrophy.
In cirrhosis there is often marked atrophy of the right lobe of the liver. At the same time there is often caudate hypertrophy principally on the left side of the vena cava. This causes rotation of the liver towards the right side. Other causes of right lobe atrophy include cholangiocarcinoma or abscess. The same phenomenon occurs in iatrogenic right portal vein embolization with atrophy of the right lobe and compensatory hypertrophy of the left side of the liver.
This liver rotation often leads to rotation of the portal vein and porta hepatis. It is important to recognise that this can occur, because the anatomy can become quite confusing depending on the degree of rotation. Similarly a completely different angle of dissection needs to be employed in dissecting the plane between the left and right portal vein branches in the hilus.
At the hilus of the liver rotation to the right can lead to the right and left branches of the portal vein no longer lying side by side but the left portal vein can lie in front of the right.
Cross section of the portal veins immediately above the level of bifurcation
Health Right lobe atrophy
Lower down the porta hepatis the typical “Mickey Mouse” conformation of the Portal vein common bile duct and hepatic artery can be distorted so that the common bile duct lies laterally to the portal vein and the hepatic artery is pulled over to the right lying anterior or on the right side of the portal vein.
Rotation of the porta hepatis occurs most closest to the centre of rotation which in this case is the liver. As you travel inferiorly towards the pancreas the degree of rotation becomes smaller. This is particularly the case as the splenic vein insertion behind the neck of the pancreas limits rotation of the portal vein at that point.
Viewed from anteriorly this rotation of the porta hepatis can result in the common bile duct lying more laterally than normal and the hepatic artery spiralling around the front of the portal vein.
Longitudinal view of porta hepatis with standard anatomy
Longitudinal view of porta hepatis with distorted anatomy due to rotation secondary to right lobe atrophy. NB left portal vein lies in front of right PV and CBD and HA are shifted to right side.
Rotation of the porta hepatis to the left can occur, usually when there is a very large space occupying lesion such as a tumour, cyst or abscess in the right lobe. The degree of rotation to the left is usually much smaller than toward the right and left lobe atrophy alone rarely causes rotation of the portal vein or porta hepatis.
Understanding and anticipating rotation of the anatomical elements of the porta hepatis in the presence of liver atrophy and hypertrophy is key to avoiding confusion and potential inadvertent vascular or biliary injury in these often challenging cases.