Pulmonary arteriovenous malformations (PAVMs)

Imaging description Arteriovenous malformations (AVMs) are abnormal connections between arteries and veins. Pulmonary AVMs (PAVMs) can be virtually any size, but are most typically between 1 and 5 cm. They can be single or multiple, and can be found anywhere in the lungs, although they are slightly more prevalent in the lower lobes [1]. The AVM consists of one or more feeding arteries and a draining vein, connected by either a large single sac, a plexiform mass of dilated vascular channels, or a direct artery–vein connection which is dilated and often tortuous. The lesions usually appear as nodular opacities on CT and the feeding arteries and draining veins are typically identifiable as tubular structures medial to the nodular opacity (Figures 54.1–54.3). Contrast is usually not needed to make the diagnosis, but when administered PAVMs usually enhance intensely, although this may not be visible in very tiny or thrombosed PAVMs. Importance Most patients (70–90%) with pulmonary AVMs have hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome. In this syndrome, these lesions are present at birth, however, they usually are not clinically apparent until adulthood. CT is useful in confirming the diagnosis of PAVM by demonstrating the feeding and draining vessels, characterizing the AVMs as simple (single feeding vessel, more straightforward to treat) or complex (multiple feeding vessels), and for measurement of feeding vessel size since embolization therapy is usually restricted to those with feeding vessels of 3 mm or greater [2].