18 Non - Invasive Endoscopy Technique - Virtual Colonoscopy

Colorectal carcinoma ranks third in frequency among all cancers. With regards to cancer related mortality, colorectal carcinoma is known as the second cause (Levin et al., 2003). This condition accounts for 10% of all cancer related mortalities in women and men. Overall, lifetime risk for the development of colorectal carcinoma is still 5%. (Eddy, 1990) The wellknown risk factors are age, inheritance, inflammatory bowel disease, and environmental and dietary factors. Despite these risk factors, any individual factors could not be demonstrated in 75-80% of cases. Nevertheless, it is reported that most of the colorectal cancers originate from polyps. Colonic polyps are described as overgrowths of colonic mucosa regardless of histological findings (Van Dan, 1995). Vast majority of colorectal carcinomas originate from adenomatous polyps. This theory called adenoma-carcinoma sequence has been widely accepted (Hawk & Levin, 2005). Colonic polyps are divided as: non-neoplastic, which has no risk or low risk of developing cancer (hamartomatous, inflammatory, hyperplastic); and neoplastic which has low risk of developing cancer (tubular adenoma, villous adenoma, tubulovillous adenoma). Histopathological analysis has an important place in the discrimination of polyps (Erdem et al., 2005; Netzer et al., 1998). The size of the polyps has an important role for the occurrence of invasive cancer (Altıparmak et al., 2001). Small polyps with size less than 1 cm have a low rate of developing invasive cancer. However, this rate increases, as the polyps get larger (Su et al., 2005; Yamaji et al., 2004). Colonic polyps are overgrowths with a slow progress that carry a small risk of malignant transformation. However, colonic polyps constitute an important predisposition to colon cancer, and therefore these neoplasms should be removed when detected. Understanding the fact that development of colorectal carcinoma starts with mucosal lesions, the visualization of colon, early diagnosis of the lesions and the initiation of treatment have gained much importance. The determination of precancerous adenomatous polyps and cancer at an early stage with screening reduces mortality and morbidity associated with colon cancer (Chao et al., 2004; Van Dan, 1995). Thus, American Cancer Association emphasized the importance of screening in colon cancer (Jemal et al., 2002). It is possible to detect and treat polyps at a very early stage with various screening methods. This feature different from some other types of cancer enables prevention or early