Fluorescence Endoscopy for Further Workup of Neoplastic Lesions in Ulcerative Colitis Using Local 5-Aminolaevulinic Acid-Induced Photosensitization

Abstract

Background: Because the detection of neoplastic lesions in long-standing ulcerative colitis (UC) by conventional colonoscopy is difficult, there is a need for better endoscopic visualization tool. Recent studies suggest that new endoscopic imaging methods such as high-magnification chromoendoscopy (HMC), narrow band imaging (NBI), auto fluorescence imaging (AFI) may improve the detection of neoplasia and permit targeted biopsies. However, invisible neoplasia may still exist even using these novel techniques. Fluorescence endoscopy (FE) using 5-aminolaevulinic acid (5-ALA), a sensitizer which accumulates selectively neoplasia may be useful for the detection of UC associated invisible neoplastic lesions. The aim of this study was to evaluate the usefulness of FE for further workup of neoplastic lesions in patients with UC. Methods: Ten UC patients with proven neoplastic lesions or indefinite for dysplasia of colorectal mucosa, which were pointed out by other endoscopic imaging methods were enrolled. Fifteen examinations with FE were performed after local sensitization with 5-ALA solution by spray catheter. Biopsies were taken from fluorescence-positive areas and non-fluorescence surrounding areas of flat lesions for histological diagnosis. Results: All neoplastic lesions (flat dysplasia: 1, polypoid dysplasia: 1, carcinoma: 1, sporadic adenoma: 3), which were already known by prior endoscopic examinations showed fluorescence. Four lesions of indefinite for dysplasia also showed fluorescence. In addition, 4 neoplastic lesions (flat dysplasia: 2, polypoid dysplasia: 1, sporadic adenoma: 1), which were undiscovered by prior examinations were newly detected in biopsies from fluorescence-positive areas. With particular reference to newly diagnosed flat dysplasia by FE, reexamination using HMC, NBI and AFI could not point out these 2 lesions. Thirty-two false fluorescence-positive lesions were also found out. False positive fluorescence was mainly associated with microscopic hyperplastic regenerative mucosa. No neoplastic lesions were found in biopsies from non-fluorescence areas. No major adverse effects were observed in this study. Conclusions: FE after 5-ALA sensitization could be a possible unique tool for visualizing UC associated non-visible neoplastic lesions that might be overlooked by other endoscopic techniques. FE permits more detailed reexamination of UC associated neoplastic lesions, and may thus be helpful for targeted follow-up of flat low-grade dysplasia.