Pulmonary arteriovenous malformations are abnormal direct connections between the pulmonary arterial and venous systems forming a right to left shunt. Lesions may be single or multiple and are frequently discovered as solitary pulmonary nodules on chest x-ray. Many are associated with Rendu-Osler-Weber syndrome and autosomal dominant disorder. Most often lesions are asymptomatic but they may present with symptoms related to arteriovenous shunting. Symptoms may include hypoxia, dyspnea, hemoptysis, and possibly from embolic events.

On chest x-ray finding is usually a pulmonary nodule, possibly with a visible feeding vessel extending from the hilum. On CT, lesions appear somewhat lobulated and well defined, also with feeding and draining vessels emanating from and to the hilum. The vascular nature of these lesions is well defined with characteristic intravenous contrast enhancement. Similar findings can also be seen on pulmonary angiography.

Important radiographic criteria include feeding vessel thickness, overall size, and shunt fraction. Lesions are typically recommended for treatment with the feeding vessel is > 3 mm, the lesion is > 2 cm in size, or the shunt fraction is > 12-15 %. Treatment may be surgical or endovascular.

Treatment is intended to reduce right to left shunting and subsequently to reduce the risk of venous to arterial embolization.



References:

1. Armstrong P. et al. Imaging of Diseases of the Chest. 3rd Edition. Mosby 2000:708-711
2. Click for HyperLink