Anatomy

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The middle esophageal constriction is reached at approximately 27 cm. It is the first definite landmark that is seen in passing through the otherwise featureless cervical and upper thoracic esophagus. It is an asymmetrical luminal constriction caused by indentations from the aorta and left main bronchus (Table 2.3).

The aorta and bronchus are difficult to identify as such in the endoscopic image, and it can be difficult to appreciate their spatial relationships. It is necessary to know the anatomy of this region and the orientation of the endoscope (Figs. 2.12, 2.13).

The aorta indents the esophagus from the lateral side and runs almost horizontally as it crosses the esophagus (Fig. 2.14a). The left main bronchus indents the esophagus from the anterior side. In the endoscopic image, it runs obliquely downward in a counterclockwise direction (Fig. 2.14b, c). It has a slightly ribbed surface. A posterior indentation from the spinal column is often seen opposite the bronchus. The aorta and bronchus cannot always be positively identified. Bizarre shapes are sometimes noted in thin patients.

14 cm

Upper esophageal sphincter

14 cm

Upper esophageal sphincter

Esophagus Anatomy

Thoracic esophagus

Lower esophageal sphincter

Diaphragm

Fig. 2.12 Midesophageal constriction.

from the anterior aspect

Standard anatomical view

Thoracic esophagus

Lower esophageal sphincter

Diaphragm

Fig. 2.12 Midesophageal constriction.

from the anterior aspect

Standard anatomical view

Table 2.3 Midesophageal constriction

► Approximately 27 cm from the incisor teeth

► Indented by the aorta

► Indented by the left main bronchus

Fig. 2.13 Cross section at the level of the midesophageal constriction. To understand the appearance of the midesophageal constriction in the upper image, it is necessary to know the rotational position of the endoscope. In this figure the indentation from the spinal column is approximately at the 12-o'clock position. The left main bronchus is at the 6-o'clock position, and the aortic arch is on the right. Notice that the aortic arch is more proximal than the bronchus and runs almost horizontally. The left main bronchus is distal and runs counterclockwise down below the aortic arch a = aorta re = retrocardial esophagus l mb = left main bronchus r mb = right main bronchus

- Fig. 2.14 Crosssections

I mb = left main bronchus r mb = right main bronchus

a Level ofthe aorticarch. Notice thatthis section is still proximal to the tracheal bifurcation, and the esophagus is indented onlyfrom theside bythe aorticarch. The impression from the left main bronchus is seen distally in the endoscopic image

b Level ofthe left main bronchus. Notice thatthis section is just belowthe aortic arch. The esophagus is indented bythe left main bronchusatthislevel

c Below the left main bronchus. The esophagus is indented only bythe spinal column atthe level ofthe cross section. The cardiac impression is seen distally in the image

Anatomy

Table 2.4 Retrocardiac esophagus

The retrocardiac esophagus begins approximately 30-38 cm from the incisor teeth. It is curved posteriorly at this level due to displacement by the heart (Fig. 2.15; Table 2.4).

The retrocardiac esophagus is visualized just below the middle esophageal constriction. This portion of the esophagus is compressed anteriorly by the left atrium and posteriorly by the aorta for a length of 8 cm, resulting in an elliptical lumen (Figs. 2.16, 2.17). Distinct pulsations can be seen.

► Approximately 30-38 cm from the incisor teeth

► Elliptical indentation from the heart and aorta

► Bowed posteriorly, then curves forward toward the diaphragm

Fig. 2.15 Lateral chest radiograph after oral contrast administration. Midsagittal view of the retrocardiac esophagus. Notice that the entire esophagus is bowed posteriorly and is indented from the front by the heart

Fig. 2.17 Retrocardiac esophagus in cross section. Notice that the esophagus is symmetrically indented from the anterior side. The descending aorta is posterolateral to the esophagus a = aorta s = stomach h = heart

Fig. 2.16a, b Retrocardiac esophagus.

This region shows pulsatile changes in luminal shape b

Fig. 2.16a, b Retrocardiac esophagus.

This region shows pulsatile changes in luminal shape

Fig. 2.17 Retrocardiac esophagus in cross section. Notice that the esophagus is symmetrically indented from the anterior side. The descending aorta is posterolateral to the esophagus a = aorta s = stomach h = heart

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