Abernethy malformations are rare vascular anomalies of the splanchnic venous system. They consist of congenital portosystemic shunts and result from persistence of the embryonic vessels.
Type I malformations are thought to occur only in females, while type II have a male predominance .
There are two main types of Abernethy malformations that have been described (initially devised by G Morgan and R Superina ):
- 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
- hepatopulmonary syndrome
- pulmonary arteriovenous fistulae
- thought to arise due to hyperammonemia
- may lead to systemic emboli
- other congenital abnormalities, particularly associated with type I :
History and etymology
Named after John Abernethy, who gave the first account of an absent portal vein with accompanying congenital mesentericocaval shunt in 1793.