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Abernethy malformations are rare vascular anomalies of the splanchnic venous system. They consist of congenital portosystemic shunts resulting from the embryonic vessels' persistence.
Type I malformations are thought to occur only in females, while type II has a male predominance 1.
Two main types of Abernethy malformations have been described 6:
type I: end-to-side shunt; superior mesenteric and splenic vein drain separately into inferior vena cava
type II: side-to-side shunts; superior mesenteric vein and splenic vein form a common trunk before draining into the inferior vena cava
In type I shunts (end-to-end), there is a congenital absence of the portal vein with a complete diversion of portal blood into systemic veins (inferior vena cava, renal veins, or iliac veins). These are further subdivided into:
type Ia: separate drainage of the superior mesenteric vein and splenic vein into systemic veins
type Ib: superior mesenteric vein and splenic vein join to form a short extra-hepatic portal vein which drains into a systemic vein (inferior vena cava, right atrium or iliac veins)
In type II shunts (side-to-side), there is a hypoplastic portal vein with portal blood diversion into the inferior vena cava through a side-to-side, extrahepatic communication.
hepatic encephalopathy: from portosystemic shunting
hepatic mass lesions
thought to arise due to hyperammonemia
may lead to systemic emboli
other congenital abnormalities, particularly associated with type I 1:
History and etymology
Named after John Abernethy, who gave the first account of an absent portal vein with accompanying congenital mesentericocaval shunt 1,5 in 1793.