The Z-line, the boundary between the esophageal and gastric epithelium, should be identified, localized, and evaluated in every upper endoscopy. The location of the Z-line is measured in centimeters from the incisor teeth, with a normal range of 3640 cm. The relation of the line to the esophageal hiatus should also be described. This relation is variable and depends upon respiration, the axial pressure applied with the endoscope, and constitutional factors. The Z-line is located at or slightly above the level of the esophageal hiatus.

The endoscopic appearance of the Z-line is highly variable (Fig. 2.23). It usually has a jagged or undulating shape and is basically symmetrical. The gastric mucosa appears redder, fresher, and slightly raised in relation to the pale pink or gray epithelium of the esophagus. The boundary line may be very irregular; "flames" of gastric mucosa may project into the esophagus, just as tongues of esophageal epithelium may extend downward. These extensions may be largely uniform and symmetrical, or they may have a completely asymmetrical aspect. Occasionally the epithelial boundary appears blurred or indistinct, but usually it is sharply defined. The line may show hyper-trophic thickening or may even form a functionally active ring.

Schematic diagrams and illustrative endoscopic images. The normal range of variation is large.

a Ring-shaped b Jagged c Flame-shaped a Ring-shaped b Jagged c Flame-shaped

Endoscopy is not the best method for evaluating esophageal motility and its disorders. Nor is it useful for characterizing esophageal motility due to artifacts caused by air insufflation, stretching of the esophageal wall, contact with the endoscope, and gagging by the patient. Nevertheless, relatively gross abnormalities of esophageal motility can be appreciated during en-doscopy. The examiner should take time to observe esophageal peristalsis, particularly when investigating swallowing difficulties, obstruction-related symptoms, and noncardiac chest pain.

peristalsis). Gagging is associated with fine contractions that cause a rippling of the esophageal surface. Bizarre patterns are occasionally caused by contractions of the circular and longitudinal muscles. These phenomena of esophageal motility are observed even in healthy, asymptomatic patients. Abnormalities of esophageal motility like those seen in achalasia (p. 81 f.) and nutcracker esophagus are described in a later section (p. 84 f.).

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