Abernethy malformations manifest as hepatopulmonary syndrome, pulmonary vasculopathy, or encephalopathy. A novel intervention in a child with portosystemic shunt and inferior caval vein hypoplasia led to complete normalisation of hypoxia and relief of obstruction in the inferior caval vein. Embryological explanations of venous anomalies may indicate that inferior caval vein anomalies are frequent but under-recognised in patients with Abernethy malformation.

Severe cyanosis due to pulmonary arteriovenous fistulas occurs often after a bidirectional superior cavopulmonary anastomosis (Glenn operation) and also in some congenital anomalies in which hepatic venous blood bypasses the lungs in the first passage. Relocation of hepatic flow into the lungs usually causes these fistulas to disappear. Similar pulmonary arteriovenous fistulas are observed in hereditary haemorrhagic telangiectasia, and in liver disease (hepatopulmonary syndrome). There is no convincing identification yet of a responsible hepatic factor that produces these lesions. Candidates for such a factor are reviewed, and the possibility of angiotensin or bradykinin contributing to the fistulas is discussed.

Pulmonary arteriovenous fistulas are vascular malformations, which, by virtue of producing abnormal vascular connections proximal to the units of gas exchange, result in intrapulmonary right-to-left shunting. These malformations or fistulas reflect at least in part disordered angiogenesis, and less commonly recruitment and dilation of pre-existing vascular channels.1 Pulmonary arteriovenous fistulas occur in a number of diverse clinical settings. Such fistulas are a well-established feature of the Weber–Osler–Rendu complex, or hereditary haemorrhagic telangiectasia, an autosomal dominant vascular dysplasia characterized by mucocutaneous telangiectasis, epistaxis, gastrointestinal haemorrhage, and arteriovenous malformations in the lung, brain, liver and elsewhere.2,3 They are also seen in the patient with acute or chronic liver disease, disease that is usually but not invariably severe, or those with non-cirrhotic portal hypertension. They may occur as congenital malformations, single or diffuse, large or small in isolation, and when large or extensive enough may result in hypoxaemia, clinical cyanosis, and heart failure.3 Cerebral vascular accidents are also a well-known complication of this disorder.3 An extensive literature has accumulated with regard to the pulmonary arteriovenous fistulas seen in the setting of the Weber–Osler–Rendu complex, and there is considerable information on the genetics, basic biology, clinical findings, complications and therapeutic interventions of these malformations in the setting of this syndrome.4 These issues, however, are not the primary considerations of this review, although some aspects of this fascinating disorder will be discussed later. Rather the focus will be on pulmonary arteriovenous malformations that develop in the setting of cavopulmonary surgery, and their relationship to the pulmonary arteriovenous fistulas occurring in the hepatopulmonary syndrome. The complex tapestry of these overlapping and intersecting clinical observations will be unfolded in the light of their chronology.