Congenital extra-hepatic portosystemic shunt (Abernethy malformation)

Case contributed by Dalia Ibrahim
Diagnosis certain
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Presentation

Severe rectal bleeding, his physician suspects colonic angiodysplasia.

Patient Data

Age: 8-year-old
Gender: Male
  • Congenitally absent portal vein.
  • The patent superior mesenteric and the splenic veins drain the portal blood into a large anomalous vein (inferior mesenteric vein) which drains and ends finally into the right iliac vein.
  • All the forementioned veins appear patent and homogenously enhancing.
  • Normal appearance of the abdominal aorta with no aneurysmal dilatation or intimal flap dissection.
  • Patent celiac trunk, superior and inferior mesenteric as well as both renal arteries.
  • No evidence of aneurysmal dilatation, AVMs, or angiodysplasias.
  • No evidence of stenotic segments or dissection intimal flaps. 
  • Patent both common iliac, external and internal iliac arteries.
  • The liver is of average size showing multiple variable sized bi-lobar focal lesions (namely at segment II,III, IV,VI VIII & VII), the largest is seen at segment VIII/VII measures 3.3 x3.2 cm along its max dimensions, they show early arterial enhancement, with progressive fill in of contrast, the largest showing small hypodense central foci (likely representing focal nodular hyperplasia)

  • Bilateral undescended testes, which are seen within both inguinal canals.

  • Normal splanchnic arterial system. 
  • Congenitally absent portal vein.
  • The patent superior mesenteric and the splenic veins drain the portal blood into a large anomalous vein (inferior mesenteric vein) which drains and ends finally into the right iliac vein.
  • Congenitally absent portal vein.
  • The patent superior mesenteric and the splenic veins drain the portal blood into a large anomalous vein (inferior mesenteric vein) which drains and ends finally into the right iliac vein.

Case Discussion

In this case the major findings include; absent portal vein, giant inferior mesenteric vein and multiple hepatic focal lesions. 

Abernethy malformations are an extremely rare anomalous group of the splanchnic venous system. They comprise of congenital portosystemic shunt and results from persistence of embryonic vessels. 

Types

 Abernethy malformation is an anatomical classification of portosystemic anomalies consisting of:

  •  Type 1 , there is complete diversion of portal blood into the systemic circulation (end-to-side shunt), with absent intrahepatic portal branches. Type 1 shunts are further subdivided into:
    • Type 1a: those in which the splenic vein (SV) and superior mesenteric vein (SMV) drain separately into a systemic vein.  
    • Type 1b:  those in which the SV and SMV drain together after joining to form a common trunk .
  • Type 2, the intrahepatic PV is intact, but some of the portal flow is diverted into a systemic vein through a side-to-side shunt.

Clinical classification of congenital extrahepatic portosystemic shunts consist of:1

  • Type A,  In type A, the supramesenteric vein (SMV) and splenic vein (SV) drain directly into the inferior vena cava (IVC).
  • Type B, the SMV and SV drain into the left renal vein.
  • Type C, the SMV and SV drain into the iliac vein via a dilated inferior mesenteric vein. (As in this case)

In type C patients, collaterals can develop between the inferior mesenteric and iliac veins mainly via the hemorrhoidal plexus. 1

Associations

Recognized associations include:

 

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