THE MORPHOLOGICAL TISSUE-RESPONSE OF THE PIGLET ESOPHAGUS TO EXPERIMENTAL IRRADIATION BY 1320 NM ND-YAG LASER

The oesophagus of 18 minipiglets was exposed to endoscopic intralumina l irradiation with a 1320 nm Nd:YAG laser (10 W, 20 s) via a radial ap plicator with strictly radially symmetric light distribution. Immediat ely and at 2, 3, 4 and 8 wk after irradiation, the oesophagus was perf usion-fixed and filled with contrast solution. Radiographs were taken for evaluation by microradiometry. The specimens were subsequently pre pared for light and transmission electron microscopy. The immediate re action to irradiation was a morphological gradient of damage extending from the centre of the laser exposure where there was cellular thermo necrosis in all layers of the wall and condensation of the extracellul ar matrix, to a peripheral zone (at a distance of up to 8 mm from the region where the laser was centred) which showed only minor tissue dam age manifested by intracellular vacuolation. In this zone dilatation o f most vascular lumina was prominent. In the period between 2 and 8 wk after irradiation all phases of wound healing were observed and resul ted in occlusion of the lumen of the oesophagus by early scar tissue a fter an interval of more than 3 wk at the former centre of laser expos ure. Peripherally, epithelial regeneration resulted in a new luminal l ining. Both the process of epithelial regeneration and that of fibrous repair indicated a good reparative capacity of laser-irradiated oesop hageal wall tissues resembling the phases of normal wound healing. The immediate laser interaction with tissue indicated that the noncellula r matrix components of tissues are more resistant to the photothermal effect than the cellular components.