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[The change in laser usage in gastroenterology--the status in 1997].

Since the establishing of laser technology in gastroenterology there has been a change in the indications for laser therapy and numerous new laser systems have been introduced in basic and clinical research. First the argon laser and later on the Nd:YAG laser were used mainly for bleeding peptic lesions, today emphasis is on palliative desobliteration of advanced esophageal and rectosigmoidal carcinoma. Moreover, in selected cases it is used for curative ablation of early carcinoma and dysplasia. A new field of application is photocoagulation of the "watermelon stomach". Despite of promising ablation results the erbium:YAG and holmium:YAG laser became not yet established in gastroenterology. Also the KTP laser is rarely used e.g. for treatment of telangiectasia. Difficult bile duct stones can be highly effective fragmented intracorporally by means of laser lithotripsy; an automatic stone-tissue discrimination system avoids uncontrolled injury of the bile ducts. The hitherto experimental interstitial laser therapy of primary and secondary liver malignancies shows excellent results, but online monitoring of the expansion of the necrosis is still a problem. Thermal probes, MRT technology and duplex sonography are under current evaluation. Photodynamic therapy (PDT) is now, after numerous pilot studies, investigated with larger numbers of patients. First results show a marked effectiveness in ablation of dysplasia and mucosal carcinoma. The photosensitizer 5-aminolaevulinic acid seems to be particularly effective for ablation of Barrett's mucosa and m-THPC for treatment of local carcinoma. Palliative PDT of bile duct cancer may help to avoid repeated endoprosthetic treatment. The possibilities and limitations of light induced fluorescence diagnostics of severe dysplasia and carcinoma in situ is now being evaluated intensively. This method might in future facilitate the endoscopic diagnosis of dysplasia in Barrett's esophagus and chronic inflammatory bowel disease.