towards its next bifurcation, the azygos arch (AzAr), right pulmonary artery (RPA), and right pulmonary vein (RPV) are shown.
Figure 1.9 Endobronchial view of the carina, showing the right (RMB) and left (LMB) mainstem bronchi.
Figure 1.10 Endobronchial view of the first branch of the right mainstem bronchus towards the right upper lobe (RUL) and the bronchus intermedius (BI).
Figure 1.11 Endobronchial view of the bifurcation of the bronchus intermedius towards the right middle lobe (RML) and the right lower lobe (RLL).
Figure 1.12 Endobronchial view of bifurcation of the left mainstem bronchus towards the left upper lobe (LUL) and left lower lobe (LLL).
The plane is brought back to the carina to visualize the left mainstem bronchus (LMB), and the azygos arch (AzAr), aortic arch (AoAr), left pulmonary artery (LPA), and vein (LPV) are identified. The branching to the left upper lobe (LUL) and left lower lobe (LLL) are shown, and the aorta (Ao) and left pulmonary artery are labeled.
Figure 1.13 A Visible Human Model of the bronchial tree.
Chapter video clips
Video 1.1 Esophageal‐related models and cross‐sectional anatomy: radial orientation.
Video 1.2 Esophageal‐related models and cross‐sectional anatomy: linear orientation.
Video 1.3 Gastric‐related models and cross‐sectional anatomy: radial orientation.
Video 1.4 Gastric‐related models and cross‐sectional anatomy: linear orientation.
Video 1.5 Duodenal‐related models and cross‐sectional anatomy: radial orientation.
Video 1.6 Duodenal‐related models and cross‐sectional anatomy: linear orientation.
Video 1.7 Male rectum‐related models and cross‐sectional anatomy: radial orientation.
Video 1.8 Male rectum‐related cross‐sectional anatomy: linear orientation.
Video 1.9 Female rectum‐related cross‐sectional anatomy: radial orientation.
Video 1.10 Female rectum‐related cross‐sectional anatomy: linear orientation.
Video 1.11 Arterial models.
Video 1.12 Venous models.
Video 1.13 Bronchial anatomy in a linear orientation.
2 Esophagus: Radial and Linear
James L. Wise and John C. Deutsch
Essentia Health Care Systems, Duluth, MN, USA
Layers of the esophageal wall
Staging the depth of involvement of tumors and the layer of origin of subepithelial masses is an important component of competency in endoscopic ultrasonography (EUS). An intimate knowledge of the normal layers of the esophageal wall is critical for this to be done accurately. The wall of the esophagus has four readily appreciable layers by EUS using standard operating frequencies (5–12 MHz). The layers are seen in concentric, alternating rings of hyperechoic and hypoechoic structures emanating out distally from the tip of the endoscope. Starting with the layers closest to the scope tip, they are as follows:
Interface echo between the superficial mucosa and water (hyperechoic).
Deep mucosa (hypoechoic).
Submucosa plus the acoustic interface between the submucosa and muscularis propria (hyperechoic).
Muscularis propria minus the acoustic interface between the submucosa and muscularis propria (hypoechoic).
If a higher resolution frequency probe is used, greater number of layers could be visualized as detailed in Chapter 4. The esophagus lacks an obvious fifth layer as there is no serosa.
In our opinion, visualization and discernment of the layers of the esophageal wall is usually best accomplished using radial compared to linear instruments.
Figure 2.1 shows the esophageal walls using radial and linear instruments. To help separate the layers, these images include a muscularis mucosae leiomyoma that was subsequently resected. Images show subepithelial hypoechoic lesion in echolayer II as well as in the other defined layers of the esophageal wall.
Normal radial extraesophageal anatomy (Video 2.1)
Standard examination of the esophagus and mediastinum begins with advancing the radial instrument to the gastroesophageal (GE) junction at or near the squamocolumnar junction. At this level the aorta is seen as an anechoic circular structure in the 5 o’clock position. The descending aorta is kept in this position as all radial mediastinal imaging will then correlate quite nicely with cross‐sectional imaging. Other structures visible at the level of the GE junction are the inferior vena cava (IVC) seen between 7 and 9 o’clock and the liver between 6 o’clock and 12 o’clock
