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Chest Imaging

Pulmonary arteriovenous malformation

(PAVM), abnormal communication between the pulmonary artery and the pulmonary vein in which there is no capillary network. PAVM causes a rightleft shunt because blood passing through the arteriovenous fistula reaches the left atrium without being oxygenated. PAVMs may be single or multiple. They can also be simple or complex. Simple malformation is defined by a single feeding artery and a single draining vein. A malformation is complex if there are two or more feeding arteries, and two or more draining veins. Approximately 50% of patients with PAVM are patients with Osler Rendu Weber disease. Most patients are asymptomatic. Dyspnoea and cyanosis may occur in the case of a large shunt. Stroke and brain abscess may occur because of the right to left shunt, and this justifies the preventive treatment of this malformation.

Chest radiographs often show a complex lobulated or serpiginous opacity associated with tortuous feeding arteries and draining veins. The visibility of a dilated artery originating from the hila, and the dilated draining vein joining the left atrium are suggestive of the diagnosis. However, smaller lesions may be subtle or inapparent and the lesion may be manifested as a solitary pulmonary nodule. In such cases, associated abnormal vascularization may be visualized only on CT. The typical morphology of the malformation allows an easy recognition and detection on CT either with or without contrast medium injection. Spiral CT scanning with three-dimensional shading surface reconstruction is highly recommended (Fig.1). It is as effective as angiography in both the detection of small PAVM, and the delineation of the angioarchitecture of the malformation. Such assessment is necessary to plan embolotherapy (PAVM embolotherapy). Pulmonary angiography is performed selectively and can be guided the results of spiral CT examination. Pulmonary angiography is not essential for the diagnosis but remains the first step for guiding embolotherapy.

PG

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Fig.1

Nonenhanced spiral CT scan (a) and three-dimensional shading surface display (b) of a simple PAVM depicted in a patient with OslerRenduWeber disease. The lesion is located within the anterobasilar segment of the left lower lobe (arrow). The 3D-SS image permits analysis of the malformation and the draining vein and feeding artery.
Pulmonary arteriovenous malformation, Fig.1 (a)
Pulmonary arteriovenous malformation, Fig.1 (b)