Anatomy

The lower esophageal sphincter is an approximately 3-cm-long (2-4 cm) segment in the distal esophagus. It can be identified manometrically by its resting pressure of 15-25 mmHg and, less confidently, by its anatomical features. The sphincter zone lies partly above and partly below the diaphragm in the region of the esophageal hiatus. The Z-line in its lower portion marks the boundary between the esophageal squamous epithelium and gastric columnar epithelium (the squamocolumnar junction).

Endoscopically, the action of the tightly closed sphincter in a healthy subject creates a rosette pattern with four to six longitudinal folds in the distal esophagus (Fig. 2.22 a). Viewing from a level just above the sphincter, especially with air insufflation, will reveal per istaltic waves followed by a transient opening of the sphincter segment, briefly exposing the Z-line and the interior of the stomach (Fig. 2.22 b, c). Following careful inspection of this region, the endoscope is gently advanced at a moment when the sphincter is relaxed. The action of the diaphragm muscles can often be seen as respiration-dependent luminal constrictions, especially if the sphincter does not close too tightly. The examiner evaluates the sphincter segment, its distance from the incisor teeth, its functional competence, and the diaphragmatic hiatus. It is particularly important to assess whether the lower esophageal sphincter is competent or incompetent, although this assessment varies considerably among different examiners. The position of the diaphragmatic hiatus is also assessed in relation to the incisor teeth, the lower esophageal sphincter, and the Z-line.

- Fig. 2.22 Passage through the gastroesophageal junction

Endoscope

Esophageal hiatus

Diaphragm

- Fig. 2.22 Passage through the gastroesophageal junction

Endoscope

Esophageal hiatus

Diaphragm

Sphincter zone

Z-linie Stomach

Sphincter zone

Z-linie Stomach

a The sphincter is closed and shows a typical rosettelike appearance b The sphincter is starting to open, exposing the Z-line in the lower part of the sphincter region c The sphincter is open, exposing the interior of the stomach. The areas proximal and distal to the Z-line can now be clearly evaluated a The sphincter is closed and shows a typical rosettelike appearance b The sphincter is starting to open, exposing the Z-line in the lower part of the sphincter region c The sphincter is open, exposing the interior of the stomach. The areas proximal and distal to the Z-line can now be clearly evaluated

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