Fluorescent Endoscopy and Magnification Endoscopy

■ Principle of Fluorescent Endoscopy

Fluorescent endoscopy is based on the principle that when certain chemical compounds are irradiated with ultraviolet or short-wave light, they emit light at longer wavelengths.

Exogenous fluorescence and autofluorescence. The diagnostic principle of fluorescent endoscopy is based on the differences in fluorescence between normal and abnormal tissues (inflammation, dysplasia, neoplasia, ischemia). In autofluorescence, endogenous substances within the tissue are made to fluoresce, whereas exogenous fluorescence is induced by substances that are added to the tissue, such as 5-ALA. The fluorescence may be demonstrated by spectral analysis or as a fluorescent image.

Fluorescent Endoscopy with 5-ALA

Technique

In fluorescent endoscopy, the tissue is sprayed with 5-ALA, a precursor of the endogenous photosensitizer protoporphyrin IX. It is selectively concentrated in the mucosa, showing a particular affinity for dysplastic or neoplastic areas. The mucosa is probed with a laser fiber, and the fluorescence spectrum is analyzed for an increased concentration of proto-porphyrin IX. In a second step, biopsies are taken from any suspicious areas that are identified (Fig. 4.63).

Fig. 4.63 Fluorescent endoscopy with 5-ALA

a The Barrett mucosa is probed after spraying with 5-ALA

Fig. 4.63 Fluorescent endoscopy with 5-ALA

a The Barrett mucosa is probed after spraying with 5-ALA

Suspicious areas are identified and bi-opsied

Importance

The importance of fluorescent endoscopy in the diagnosis of early neoplastic changes in the esophagus and stomach is currently being evaluated.

■ Magnification Endoscopy

Principle. Magnification endoscopy, known also as zoom endos-copy, can be used for the detailed endoscopic evaluation of suspicious areas, especially after staining (Fig. 4.64).

Limitations and importance. The main limitation of magnification endoscopy is that the lesions must first be detected by con ventional endoscopy before they can be examined under magnification. This problem may be solved by the use of high-resolution instruments (high-resolution endoscopy). The importance of the method in the early detection of malignant lesions is currently being investigated.

Fig. 4.64 Magnification endoscopy a Unmagnified view of Barrett epithelium. The area was sprayed with acetic acid to heighten contrast b Magnified view of the Barrett epithelium c At higher magnification, the gyriform structure of the Barrett epithelium can be appreciated. Lesions appear as structural irregularities

Fig. 4.64 Magnification endoscopy a Unmagnified view of Barrett epithelium. The area was sprayed with acetic acid to heighten contrast b Magnified view of the Barrett epithelium c At higher magnification, the gyriform structure of the Barrett epithelium can be appreciated. Lesions appear as structural irregularities

The location of the small intestine makes it difficult to evaluate, especially by diagnostic imaging. The detection of circumscribed pathological changes in the small intestine relies on sonographic, radiographic, scintigraphic, and increasingly on endoscopic techniques (Table 4.18).

Table 4.18 Techniques for endoscopy of the small intestine

► Sonde enteroscopy

► Push enteroscopy

► Intraoperative endoscopy

► Capsule endoscopy

■ Intraoperative Enteroscopy

► Principle: The small intestine is surgically exposed, the wall is incised, and the endoscope is manually inserted.

► Advantages

- Only method that ensures complete endoscopic visualization of the small bowel

- Allows interventional procedures

► Disadvantages

- High cost

► Complications

- Anesthesia risks

- Surgical risks

- Endoscopic risks

Sonde Enteroscopy

► Principle: A nondeflectable endoscope is introduced and is carried by peristalsis into the small intestine.

- Relatively deep penetration

► Disadvantages

- Not steerable

- Limited field of view

- No interventional options

- Lengthy procedure (several hours)

- Uncomfortable procedure

Capsule Endoscopy

Principle: The patient swallows a wireless capsule containing a video imager, light source, and transmitter. The image data are transmitted to a receiver worn on the body. Advantages

- Well tolerated

- Potential visualization of the entire small intestine Disadvantages

- Costly

- Not yet adequately evaluated

- Does not allow specimen collection

■ Push Enteroscopy

► Principle: A steerable endoscope is advanced into the small intestine.

► Advantages

- Relatively well tolerated

- Relatively short examination time (about 45 minutes)

- Steerable scope

- Allows interventional procedures

► Disadvantage

- Limited range (70 cm past the pylorus)

Fig. 4.65 Capsule endoscopy b Small oozing hemorrhage in the c Polyp in the small intestine a Angiodysplasia in the small small intestine intestine

Fig. 4.65 Capsule endoscopy b Small oozing hemorrhage in the c Polyp in the small intestine a Angiodysplasia in the small small intestine intestine

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