Which types of portosystemic shunts (PSS) do we differentiate?
Is there an easy way to memorize the classic types of PSS in the dog?
In the following I will try to explain this complex topic in an understandable fashion.
Generally it can be said...
Small breed dogs = extrahepatic
Large breed dogs = intrahepatic
Below you find a short reminder of the different types and the classification of congenital PSS. The following points have to be considered:
Additionally it is helpful to consider which PSSs are common and which are less frequently seen.
Intrahepatic PSS always insert into a hepatic vein and thus essentially into the caudal vena cava.
Origin / Course
Right divisional PSS
Central divisional PSS
Left divisional PSS
Congenital extrahepatic PSS are always single vessels! Multiple extrahepatic PSS are always acquired!
Splenic vein or left gastric vein (left sided PSS)
Gastroduodenal vein (right sided PSS):
Right gastric vein (right sided PSS)
Cranial mesenteric vein (potentially at the origin of the portal vein)
To be able to identify the form of PSS you are dealing with it is helpful to remind yourself of the normal anatomy of the portal vein.
The portal vein is entering the liver slightly to the right side. Looking at its intrahepatic branching, a short right branch is coming off the portal vein immediately after entering the liver. It is supplying the right lateral hepatic lobe and the caudate process of the caudate lobe. (N.B. depending on the anatomy text you are using, the right medial hepatic lobe is also supplied by the right branch) intrahepatic portal branch. The remaining and therefore largest portion of the liver is supplied by the left intrahepatic branch of the portal vein.
Easy way to remember:
Therefore intrahepatic PSS arising from the
But how do I differentiate a central divisional intrahepatic PSS from a right divisional intrahepatic PSS. First it is helpful to remember that central divisional PSS is rare. Therefore it is more likely to have right divisional intrahepatic PSS. Additionally: The CENTRAL divisional intrahepatic PSS is very short and resembles more a FORAMEN. Compared to the right intrahepatic shunt no loop is present.
For the extrahepatic porto-caval PSS the following applies:
The reverse as for the intrahepatic PSS is true.
Porto-azygos PSSs are the only ones in which you can see a vessel coursing dorsally to the spinal column. Additionally the azygos vein is enlarged and becomes easily visible cranial to the PSS.
Porto-phrenic PSS arise caudal to the liver. It runs in a large curve along the left side of the liver (seldom right side) towards the diaphragm. The insertion is immediately caudal to the diaphragm and appears to lie within the hepatic parenchyma.
The video starts caudally and goes cranially. Left on the screen is right in the patient.
Does “Whisky” have a PSS and if “yes” which type?
No responsiblity is taken for the correctness of this information.
© Antje Hartmann