What is a Congenital Portosystemic Shunt?
A Congenital Porto-Systemic Shunt (CPSS) is a rare vascular malformation where blood goes directly from the intestines to the heart without passing through the liver for filtration. Today we know that if the blood does not get filtered by the liver, it can cause complications at any age. It is therefore recommended that most CPSS should be closed surgically or by small devices placed in the abnormal vessel.
Anatomical types of shunts
In light blue, the mesenteric vein draining the bowel and the splenic vein draining the spleen join to form the main portal vein that enters the liver and gives the intrahepatic portal veins. This allows the blood coming from the bowel with products of digestion to be filtered through the liver before getting to the heart via the hepatic veins
In purple, the inferior vena cava drains the blood from the inferior part of the body and receives the two renal veins and the hepatic vein just before joining the heart in the right atrium.
After birth, there is no direct communication between the portal and systemic veins.
Two anatomical types of CPSS are currently classified as intrahepatic, the portohepatic shunts and the patent ductus venosus.
Porto-hepatic shunts consist of direct communications between one or several portal branches and one or several hepatic veins.
Patent Ductus Venosus is the abnormal patency of the ductus venosus that is a physiological connection between the intrahepatic left portal vein and hepatic vein during pregnancy and that normally closes spontaneously after birth. In case of malformation, the Ductus venosus remains patent.
Extrahepatic CPSS are connections between portal veins and systemic veins that can happen between the main portal vein and the IVC or upstream the portal vein from any vein afferent to the main portal vein and draining in any vein afferent to the IVC, the IVC itself of the heart itself.
Because the blood flow drains mainly through the CPSS, this malformation can cause the complete disappearance of the main portal vein and intrahepatic portal veins and is historically called Abernethy 1 malformation or congenital absence of portal vein.
This connection can cause hypoplasia of the main portal vein and its branches, historically called Abernethy 2 malformation.