Locating Stations 4R and 4L by EBUS
Both station 4R (right paratracheal) and 4L (left paratracheal) lymph nodes are accessible via EBUS-TBNA from the trachea, with 4R typically easier to visualize and sample than 4L, which often requires balloon assistance due to its more challenging angle. 1
Anatomical Access and Positioning
Station 4R (Right Paratracheal)
- Located immediately adjacent to the right lateral tracheal wall
- Accessed by positioning the EBUS scope in the trachea with the transducer oriented toward the right side
- Generally straightforward to visualize and sample via the endobronchial approach
- Part of the core stations (2L, 2R, 4L, 4R, and 7) that are reliably accessible by EBUS-TBNA 1
Station 4L (Left Paratracheal)
- Located along the left lateral tracheal wall
- Accessed from the trachea with the transducer oriented toward the left side
- More technically challenging than 4R due to the slightly difficult angle 2
- Requires careful scope manipulation to achieve optimal contact with the tracheal wall
Technical Considerations for Optimal Sampling
Balloon Use
Balloons are commonly used and recommended when targeting paratracheal stations 4R and 4L 2. The saline-filled balloon:
- Overcomes poor contact between the ultrasound probe and bronchial wall
- Enhances image acquisition, particularly important for the challenging 4L angle
- Provides better acoustic coupling for clearer visualization
- Particularly helpful for station 4L given its more difficult anatomical position
Key Practical Points
- Station 4L is accessible by both EBUS-TBNA (from the airway) and EUS-B-FNA (from the esophagus), providing alternative sampling routes if one approach is difficult 1
- Station 4R is primarily accessed via EBUS-TBNA; EUS access to 4R is difficult because the trachea lies between the esophageal transducer and the lymph node 1
- When performing comprehensive mediastinal staging, both stations should be evaluated as part of systematic nodal mapping 3
Distinguishing 4L from Adjacent Stations
Station 4L must be differentiated from stations 5 and 6 (aortopulmonary window nodes), which are located more inferiorly and laterally 4. Understanding the ultrasonic anatomical relationships is crucial for accurate station identification during EBUS procedures.
Common Pitfalls
- Inadequate balloon use for station 4L: Failure to use a balloon when sampling 4L may result in suboptimal imaging and reduced diagnostic yield
- Latex allergy: Balloons are latex-based and cannot be used in patients with latex allergies 2
- Misidentification of station 4L: Can be confused with stations 5 or 6 if anatomical landmarks are not carefully assessed 4
- Incomplete sampling: In staging procedures, both 4R and 4L should be evaluated when indicated, not just the side ipsilateral to the tumor