Light- and electron-microscopic study of the rat esophagus following intraluminal argon laser irradiation

36 rat esophagi were irradiated by argon laser via an applicator with circumferential light distribution. They were perfused with glutaraldehyde and studied by light and transmission electron microscopy immediately, 2 days and 14 days after irradiation. Immediately after irradiation the laser center showed destruction of the keratinized stratified squamous epithelium. The collagenous fibers of the connective tissue were altered; fibrocytes and fibroblasts were severely damaged, and the microvascular lumina were occluded. The smooth muscle tissue and skeletal muscle tissue showed myofilament defects and initial karyonecrosis. There was decreasing damage of both fiber types up to 4 mm from the laser center. After 2 days the morphology of the laser center was not different from that seen immediately after irradiation. At a distance of 2 mm a partly differentiated new epithelium emerged below the necrotic epithelium. An inflammatory reaction was found in the connective tissue. After 14 days the esophageal wall was replaced and the lumen was occluded by young granulation tissue in the former laser center. Peripherally the esophageal wall appeared almost normal. As the rat esophagus serves as a model for esophagotracheal fistulae in newborn children, our findings indicate that the argon laser should be capable of occluding these fistulae likewise.