What is a paratracheal stripe?

What is a Paratracheal Stripe

The paratracheal stripe is a thin, water-density stripe visible on chest radiographs between the air column of the trachea and the adjacent lung, with the right paratracheal stripe (RPS) being the most clinically significant and normally measuring 1-4 mm in width. 1

Anatomical Definition

The right paratracheal stripe represents the interface between the tracheal wall and the adjacent right lung on posteroanterior (PA) chest radiographs. 1 This stripe is composed of:

• The tracheal wall itself
• Paratracheal soft tissues including lymph nodes
• The mediastinal pleura
• Any intervening fat or connective tissue 2

Normal Measurements and Variations

In normal subjects, the RPS width ranges from 1 to 4 mm, and any measurement of 5 mm or greater is reliable evidence of pathology. 1 This measurement should be performed on standard PA chest radiographs using consistent technique. 3

Clinical Significance

Pathological Widening

A widened paratracheal stripe (≥5 mm) indicates disease in one of three anatomical compartments 1:

• Tracheal pathology: Direct involvement of the tracheal wall
• Mediastinal disease: Including paratracheal lymphadenopathy, mediastinal hemorrhage, infection, goiter, or vascular abnormalities 2
• Pleural disease: Opacifying processes in the adjacent pleura 2

Specific Applications

In blunt chest trauma, a right paratracheal stripe measuring 5 mm or greater on supine radiographs indicates mediastinal hemorrhage, with 22.9% of such cases showing major arterial injury on arteriography. 3 This makes it a quantitative and reliable indicator for determining which trauma patients require urgent arteriographic evaluation. 3

In paratracheal lymphadenopathy, widening of the RPS is seen in only 31% of cases with enlarged nodes (>15 mm), making it a relatively insensitive but specific finding. 4 CT demonstrates that enlarged paratracheal nodes are typically positioned anterolateral rather than directly lateral to the trachea, which explains why the stripe may not always be widened despite significant adenopathy. 4

Anatomical Landmarks for Lymph Node Stations

The paratracheal region is divided into upper and lower stations for lung cancer staging 5:

• Station 2R (right upper paratracheal): Located above the azygos vein 5
• Station 4R (right lower paratracheal): Located below the azygos vein but above the upper border of the left main pulmonary artery 5

The azygos vein serves as the critical anatomical landmark to differentiate these stations during both imaging interpretation and endobronchial ultrasound (EBUS) procedures. 5

Diagnostic Limitations

While the paratracheal stripe is a useful radiographic sign, chest CT is significantly more sensitive than plain radiography for detecting paratracheal lesions, particularly small lymph nodes and masses in the aortopulmonary window and paratracheal region. 6 Plain radiography can only reveal large lesions and fails to detect small clinically relevant pathology. 6

Key Clinical Pitfalls

• Do not rely solely on paratracheal stripe assessment for mediastinal staging: Only 31% of patients with enlarged paratracheal lymph nodes will show widening of the RPS on plain films 4
• Always correlate with clinical history: The differential diagnosis of a widened paratracheal stripe is extensive, and proper interpretation requires integration with clinical findings 2
• Consider CT for definitive evaluation: When paratracheal pathology is suspected, CT provides superior anatomic detail and sensitivity 6, 4