Abernethy Malformation

Abernethy malformation is a congenital portosystemic shunt that results from persistence of embryonic vessels.

Three types of Abernethy malformation have been described.

• Type I: There is a congenital absence of the portal vein with complete diversion of portal blood into systemic veins (the inferior vena cava, or renal or iliac veins).
  • Type Ia: There is separate drainage of the superior mesenteric and splenic veins into systemic veins.
  • Type Ib: The superior mesenteric and splenic veins join to form a short extrahepatic portal vein which drains into a systemic vein.
• Type II: There is a hypoplastic portal vein and portal blood is diverted into the vena cava through a side-to-side, extrahepatic communication.

Abernethy malformation has been associated with:

• Hepatic encephalopathy: Due to portosystemic shunting. Look for T1 hyperintensity in the lentiform nuclei.
• Hepatic masses: Focal nodular hyperplasia (thought to be due to the absence of the portal vein), hepatocellular carcinoma, hepatoblastoma
• Hepatopulmonary syndrome:
• Pulmonary arteriovenous fistulas: Thought to be due to hyperammonemia. May lead to systemic emboli.
• Congenital abnormalities: Cardiac defects, biliary atresia, and polysplenia.

References

Howard ER, Davenport M. Congenital extrahepatic portocaval shunts--the Abernethy malformation. J Pediatr Surg. 1997 Mar;32(3):494-7.