Esophagoscopy and Endoscopic Ultrasound
The ability of being able to introduce a flexible instrument with a chargecoupled device safely into the gastrointestinal tract has revolutionized the practice of gastroenterology. Endoscopic examination of the esophagus shows extensive detail of the mucosal lining, some imaging of abnormalities that lead to intramural or extramural indentation or compression of the lumen, respectively, and esophageal motility abnormalities as estimated by sphincter tone and esophageal diameter. Mucosal abnormalities seen are best characterized as inflammatory or neoplastic. Inflammatory lesions may vary in intensity from mild superficial erythema to frank ulceration with complete destruction of the mucosa.
This process may occur distally (e.g., gastroesophageal reflux) or proximally (e.g., lichen planus). The inflammation may also be well localized and discreet (e.g., pillinduced esophagitis), patchy (e.g., candidal esophagitis), or diffuse (e.g., radiation esophagitis or caustic injury). Inflammation may also be seen indirectly as an esophageal stricture representing a sequela of uncon trolled or poorly controlled chronic inflammation. Strictures of the esophagus may appear as bland, tapered narrowings. A stricture may be short or long, sometimes involving the entire esophagus. The diameter of the stricture may be widely patent or pinpoint, depending on the cause, and may occur in any portion of the esophagus. The most common location is the distal esophagus due to the common cause of gastroesophageal reflux. The stricture may have normal appearing overlying mucosa or frank erythema and ulceration, depending on the activity of the underlying inflammatory process.
Endoscopic ultrasound relies on standard endoscopic technology but with an ultrasound transducer at the end of the endoscope. This allows for detailed information on the layers of the esophageal wall and closely apposed structures to the esophagus. Echographically, the esophageal wall is characterized by layers of varying echodensity distinguishing the mucosa, submucosa, and muscularis propria. Newergeneration echoendoscopes may visually further subdivide these layers. This information is essential for numerous esophageal diseases, including assessment of the degree of esophageal wall penetration from a mucosal process such as neoplasia, identification of a lesion originating in a layer beneath the mucosa, and visualization of periesophageal lymph nodes and other adjacent structures, such as the aorta, heart, and lung. Furthermore, endoscopic ultrasound enhances diagnostic accuracy by allowing for placement of a fine needle into abnormal tissue beneath the mucosa and transmural aspiration of tissue for histologic analysis. Therapeutic applications are also possible by drainage of adjacent cystic structures and abscesses.