Teaching Case

A 23-year-old female presented with a complaint of intermittent dyspnea (New York Heart Association NYHA grade, II), which aggravates on exertion and mild chest pain. No past significant medical and surgical history was given by the patient. On clinical examination, bruit was heard on auscultation in the left mid-zone.

Chest X-ray (Figure 1) shows a well-circumscribed homogenous soft pulmonary nodular opacity in mid-zone of left lung (arrow) and a tubular structure arising from its medial margin and directed towards the hilum (arrowhead).

CTPA with Axial MIP image (Figure 2) shows a left lower lobe high-density, contrast-enhancing tortuous nodular opacity (arrow) with tubular structure arising from the superomedial aspect of the lesion and directed towards the left hilum (arrowhead). This is the feeding artery branch of main left pulmonary artery.

CTPA with coronal MIP image (Figure 3) shows left lobe pulmonary arterio-venous malformation demonstrating the angioarchitecture of a PAVM with a single feeding artery (down arrowhead) from the left main pulmonary artery and single vein (up arrowhead) draining into the left atrium via an inferior pulmonary vein, both connected to the tortuous contrast enhancing aneurysmal sac (nidus).

Volume rendering multiplanar reformatted image (Figure 4) confirmed the suspected diagnosis of pulmonary arterio-venous malformation by establishing vascular communications of the lesion with the origin and termination of the pulmonary arteriovenous malformation (PAVM).

Background

Pulmonary arteriovenous malformations (PAVMs) are rare, abnormal low resistance, high flow vascular structure. It is a fistulous communication between the pulmonary artery and vein bypassing the capillary bed and resulting in the intrapulmonary right to left shunt. PAVMs are often unilateral with their propensity towards the lower lobes. According to various literature, its incidence is 2–3 per 100,000 population [1]. Mostly PAVMs are associated with Hereditary Hemorrhagic Telangiectasia (HHT1 > HHT2) / Osler-Weber Rendu syndrome. It can be congenital or acquired [2]. Usually, till the second decade, it remains asymptomatic, but in puberty and pregnancy, it may show some symptoms like chest pain and dyspnea hemoptysis because of the gradual enlargement of PAVMs with age.

Clinical perspective

There are 4 variants of PAVMs:

• Simple: the commonest, comprises a single artery feeding the malformation; the feeding segmental artery may have multiple subsegmental branches [2].
• Complex: have multiple segmental arteries feeding the malformation [2].
• Diffuse: rare, it is a combination of simple and complex variants [1].
• Telangiectatic: these are typically seen in children more common in patients with telangiectasia [2].

The diagnosis of PAVMs is confirmed only if the nodule is connected with the artery and vein.

Imaging perspective

Radiologically, the condition is an important differential diagnosis of the pulmonary nodule. In our case, PAVMs are detected on Multimodality chest imaging: Roentography, Contrast-enhanced computed tomography (CECT) and Computed tomography pulmonary angiography [2].

On chest radiography, typically, PAVMs appear as well-defined homogeneous soft tissue lesions and are associated with dilated pulmonary vessels. CECT is the modality of choice for the characterization of PAVMs. A homogenous, well-circumscribed, high density, non-calcified enhancing nodule or serpiginous mass lesion connected with blood vessels, showing aneurysmal connection along with the feeding artery and draining vein related to PAVMs [3].

3D spiral CT is useful in the pre-therapeutic evaluation of the number and orientation of the feeding arteries.

CT pulmonary angiography is the gold standard modality required when further intervention is planned.

Multiplanar reformatted images confirmed the diagnosis of PAVMs by establishing the vascular communication with the lesion, with the origin and termination of PAVMs [8].

Outcome

Studies have shown that CT is the best noninvasive modality for the evaluation of pulmonary AVMs. Surgery and transcatheter embolotherapy is recommended for treatment of symptomatic patients or those AVMs having a diameter of more than 3mm. Transcatheter embolotherapy with stainless steel coils or detachable balloons is most commonly performed by interventionists [6].

Teaching points

Pulmonary AVMs are a rare clinical entity. It is usually associated with Hereditary Hemorrhagic Telangiectasia / Osler Weber Rendu syndrome. CECT chest is the best and noninvasive modality to know the description of PAVMs. After transcatheter embolotherapy, significant decrease in the size of the nodule is usually seen.