EUS imaging is performed from the esophagus and stomach. Lymph nodes can be identified in the posterior mediastinum, retroperitoneum, and celiac regions. Posterior mediastinal lymph nodes are predominantly left sided and communicate with the para-aortic lymph nodes of the abdomen; hence, evaluation of the celiac region is important. In addition, metastases may be seen in the left adrenal gland and left lobe of the liver. The mediastinal lymph node stations that can be readily imaged by EUS include the following: subcarinal (station 7) [Fig 3
, top], subaortic (station 5) [Fig 3
, bottom], paraesophageal (station 8), inferior pulmonary ligament region (station 9), and main bronchial (station 10) [Fig 1]
Lymph nodes in the left paratracheal (station 2) and left lower paratracheal (station 4) stations can be imaged and sampled, and are more accessible than the right paratracheal and lower paratracheal lymph nodes due to air interference from the trachea. Metastatic mediastinal lymph nodes were most often identified in the subcarina (station 7) and paraesophageal area (station 8) when evaluated by TEE.61
Unfortunately, lymph nodes that are far away from the esophagus, such as lobar (station 12) and interlobar (station 11), cannot be readily seen by EUS (Fig 1)
This is one limitation of EUS. Likewise, lymph nodes anterior and lateral to the trachea (station 3, station 6) cannot be imaged reliably with EUS due to air interference.28
EUS is complementary to mediastinoscopy, as aortopulmonary window (station 5) and subcarinal (station 7) lymph nodes are stations readily accessed with EUS (Fig 1)
Often, subcarinal lymph nodes cannot be accessed with mediastinoscopy.