Early Colorectal Cancer: New Diagnostic Methods And Colonoscopic Therapeutic Techniques (pp. 143-170)
Authors: Hurlstone, David P.; Kelly,Jackie (Royal Hallamshire Hospital; Sheffield, United Kingdom)
Abstract: The recognition of flat colorectal lesions and the use of chromoscopy as a diagnostic tool in colonoscopy has followed a similar evolution to gastric and early oesophageal cancers. Hence, concepts and diagnostic techniques that were used only for malignancies of the stomach and oesophagus have now been applied in colorectal cancer. Kariya et al reported the first case of a depressed lesion in 1977, but until 1994, when Kudo et al reported their flat adenoma cohort and classification, flat and depressed lesions were thought to be a unique Japanese phenomena (phantom carcinoma or Akita disease). Studies from Western groups now prove this to be incorrect. For the detection of large polyps and advanced colorectal cancers, chromoendoscopy and magnification colonoscopy is not required. The strength of the techniques are essentially in identification of flat and diminutive colorectal lesions whose detection with conventional colonoscopy is sub-optimal. Current data proposes flat adenomas may account for in excess of 30% of all colorectal lesions. In addition, malignant potential conferred in this group may be significantly higher compared to conventional colorectal polypoid lesions. Magnification colonoscopy complemented by mucosal dye spraying may therefore be a helpful diagnostic tool. Most flat colorectal lesions are small and have an innocent appearance at initial colonoscopy. Macroscopic non-magnified views commonly reveal only subtle architectural deviation, such as a modest colour change (discolour and faint redness) or a loss of the vascular net. The use of stains such as indigo carmine in addition to magnification colonoscopy can offer a quick and simple diagnostic tool in this group. This chapter explores new colonoscopic diagnostic and therapeutic techniques now available in Western practice, previously developed by Japanese groups. We discuss the controversies surrounding the diagnosis and therapeutic strategies involved in flat and depressed colorectal lesions and explore the concept of ‘virtual biopsy’ techniques as applicable to high-magnification chromoscopic colonoscopy. Finally, new and evolving diagnostic colonoscopic techniques using autofluorescence are discussed.