Endoscopy. Endoscopy involves the insertion of a long (one meter), flexible tube with a light and camera on its end through the mouth, pharynx, esophagus, and into the stomach. The lining of the pharynx and esophagus can be evaluated visually, and biopsies (small pieces of tissue) can be obtained for examination under the microscope or for bacterial or viral cultures.
Endoscopy is an excellent means of diagnosing tumors, strictures, and Schatzki's rings as well as infections of the esophagus. It also is very good for diagnosing diverticuli of the middle and lower esophagus but poor for diagnosing diverticuli in the upper esophagus (Zenker's diverticulum).
It is possible to observe abnormalities of esophageal muscular contraction, but esophageal manometry is a test that is much better suited for evaluating function of the esophageal muscles. Resistance passing the endoscope through the lower esophageal sphincter combined with a lack of esophageal contractions is a fairly reliable sign of achalasia or Chagas disease (due to the inability of the lower esophageal sphincter to relax), but it is important when there is resistance to exclude the presence of a stricture or cancer which also can cause resistance. Finally, there is a characteristic appearance of the esophageal lining when infiltrated with eosinophils that strongly suggests the presence of eosinophilic esophagitis.