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Pulmonary arteriovenous malformation

Pulmonary arteriovenous malformations (PAVM) is a rare vascular anomaly of the lung. Most cases tend to be simple AVMs (single feeding artery) although up to 20% of cases can have complex (two or more) feeding vessels 7. They can be multiple in around one-third of cases.

Epidemiology

There is a recognized female predilection.

Clinical presentation

Despite most patients being asymptomatic, the connection between the venous and arterial system can lead to dyspnea (due to right-to-left shunting), as well as embolic events (due to paradoxical emboli). Although it is assumed that the vascular defects are present at birth, they are seldom manifested clinically until adult life until when the vessels have been subjected to pressure over several decades. Clinically a murmur or bruit may audible over the lesion (especially if peripheral).

Pathology

In congenital cases they are considered to result from a defect in the terminal capillary loops which causes dilatation and the formation of thin-walled vascular sacs.

Location

These are often unilateral. Although can potentially affect any part of the lung, there is a recognised predilection towards the lower lobes (50-70%) 7.

Associations

PAVMs have been described in association with a number of conditions.

In addition PAVMs have been found in:

Radiographic features

A number of modalities are available for the diagnosis of PAVMs, including contrast echocardiography, radionuclide perfusion lung scanning, computed tomography (CT), magnetic resonance imaging (MRI), and, the gold standard, pulmonary angiography 2.

CT

CT is often the diagnostic imaging modality of choice. The characteristic presentation of a PAVM on non-contrast CT is a homogeneous, well-circumscribed, non-calcified nodule up to several centimeters in diameter or the presence of a serpiginous mass connected with blood vessels 3. Occasionally associated phleboliths may be seen as calcifications. Contrast injection demonstrates enhancement of the feeding artery, the aneurysmal part, and the draining vein on early-phase sequences.

Treatment and prognosis

Treatment options include:

  • trans-catheter coil embolisation
  • surgery

Once successfully treated (embolotherapy, surgical resection), prognosis is generally good for an individual lesion.

Complications

Differential diagnosis

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