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Paraaortic line

The paraaortic line is a normal linear interface seen on frontal chest radiographs, most commonly on the left side. It represents the interface between the air-filled left lung and the soft tissue of the descending thoracic aorta and adjacent mediastinal structures.

It is an important mediastinal contour used in chest X-ray interpretation to assess the position and outline of the descending thoracic aorta.

Synonyms

  • Left paraaortic line

  • Paraaortic stripe

Location

  • Seen along the left lateral border of the descending thoracic aorta

  • Extends vertically from the aortic arch region

  • Courses inferiorly along the left side of the thoracic spine

  • Located in the left posterior mediastinum

  • Medial to the left lung field

Anatomical basis

  • Descending thoracic aorta (medial soft-tissue component)

  • Left lung air (lateral component)

  • Mediastinal pleura

  • Thin intervening fat plane, contributing to the sharp interface

Relations

Medially:

  • Descending thoracic aorta

Laterally:

  • Left lung

Anteriorly:

  • Posterior mediastinal soft tissues

Posteriorly:

  • Thoracic vertebral bodies

Superiorly:

  • Aortic arch / aortopulmonary region

Inferiorly:

  • Descending thoracic aorta toward the diaphragmatic level

X-ray appearance

Chest radiograph (PA view):

  • Appearance: Thin, smooth, vertical or gently curving line along the left mediastinal border

  • Thickness: Typically ≤2–3 mm

  • Margins: Sharp and well-defined

  • Extent: Best visualized from the level of the aortic arch downward

  • Continuity: Usually uninterrupted and parallel to the thoracic spine

  • Visibility: Depends on lung inflation and patient positioning

CT image

Paraaortic line ct Anatomy, Location and Imaging Appearance CT anatomy image -img-00000-00000

X-Ray image

Paraaortic line x ray Anatomy, Location and Imaging Appearance CT anatomy image -img-00000-00000