Scimitar Syndrome | Figure 1

CincyKidsRad

Cincinnati Children's Radiology

Scimitar Syndrome

Image description

Frontal chest radiograph (Image 1) shows a curvilinear vascular structure along the right cardiac border consistent with a scimitar vein (arrow) and a relatively small right hemithorax. Coronal CT maximum intensity projection (image 2) demonstrates partial anomalous right pulmonary venous return, with the scimitar vein draining into the inferior vena cava.

Teaching point

Scimitar syndrome is a form of partial anomalous pulmonary venous return in which right pulmonary veins drain into the inferior vena cava. Right lung hypoplasia results in a small right hemithorax, and the anomalous descending vein produces the characteristic curvilinear “scimitar” appearance on chest radiographs. CT delineates the anomalous venous course and confirms systemic venous drainage.

Diagnosis added by author

Scimitar syndrome

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Coronal (Image 1) and axial (Images 2 and 3) contrast-enhanced CT reveal the 'hot quadrate' sign (arrow) due to superior vena cava occlusion (arrowhead). In this patient, the thrombus extends into the right atrium (arrowhead, image 3). The hot quadrate sign occurs due to collateral venous flow around the obstructed superior vena cava. In this setting, contrast passes from the upper extremity to the inferior vena cava via collateral veins such as the internal thoracic, superior and inferior epigastric, and paraumbilical veins.

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Reconstruction from a contrast chest CT performed for possible metastatic disease in a young teen shows a large pulmonary vein (red arrow) draining into the brachiocephalic vein (yellow arrow) from the left upper lung consistent with partial anomalous pulmonary venous return (PAPVR). The usual drainage of a pulmonary vein is directly to the left atrium. In PAPVR, the pulmonary vein drains into a systemic vein. There is frequently a coexistent atrial septal defect.

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Chest x-ray shows the right lung to be smaller than the left. There is a scimitar-shaped vessel coursing from the right mid chest inferiorly. Scimitar syndrome is composed of a hypoplastic right lung, scimitar vein connecting to the inferior vena cava, and systemic arterial supply to the RLL.

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Oblique coronal maximum intensity projection CT of the chest (image 1) shows a large scimitar vein (arrow) extending inferiorly. The large vein (arrow) is visible on the axial CT image (image 2) as well as chest x-ray (image 3). Scimitar syndrome, also known as hypogenetic lung represents a partial anomalous pulmonary venous return. It affects the right lung and is associated with right lung hypoplasia, cardiac dextroposition, and often abnormal systemic arterial supply to the right lung.