Differentiating 2R and 4R Lymph Node Stations in EBUS

Anatomical Landmarks and Identification

The key anatomical landmark to differentiate 2R (right upper paratracheal) and 4R (right lower paratracheal) lymph nodes during EBUS is the azygos vein, with 2R being located above the azygos vein and 4R below it 1, 2, 3
The right paratracheal lymph nodes are divided into upper (2R) and lower (4R) stations, both of which are accessible via EBUS-TBNA 1
Station 2R is located above the level of the azygos vein, while station 4R is located below the azygos vein but above the upper border of the left main pulmonary artery 2, 3

When performing EBUS, the placement of an endotracheal tube may block the ultrasonographic view of higher paratracheal lymph nodes including station 2R, and should be avoided if these nodes are the sampling target 4
For optimal visualization of station 2R, consider using an oral approach without an artificial airway or with a laryngeal mask airway positioned carefully to avoid obstructing the view 4
The EBUS scope should be positioned at the appropriate level of the trachea to visualize the azygos vein, which serves as the critical landmark 3, 5

During EBUS examination, first identify the azygos vein on the right side of the trachea using ultrasound with color Doppler to confirm vascular flow 3, 6
For station 2R examination, position the EBUS scope in the upper trachea above the level of the azygos vein 1, 3
For station 4R examination, position the scope below the level of the azygos vein but above the main carina 1, 3

Accurate identification of lymph node stations is critical for proper lung cancer staging according to the International Association for the Study of Lung Cancer (IASLC) lymph node map 1, 2
Proper differentiation between 2R and 4R has prognostic implications, as involvement of different nodal stations affects the TNM staging of lung cancer 1, 3