Neoplastic and Nonneoplastic Polyps of the Colon and Rectum

Abstract

Epidemiology PrevalenceInformation on the prevalence of polyps comes from autopsy studies and from colonoscopic surveys, which are of a much smaller scale. Autopsy studies generally show a higher prevalence of polyps and adenomas than endoscopic studies. Prevalence rates vary considerably between gender (males more common), ethnic groups, and countries, and reflect the rates of colorectal cancer in those population groups (see Chapter 63). In the United States, autopsy studies suggest an overall polyp prevalence of up to 50% [6,7], but colonoscopic surveys suggest no more than 40% [8][9][10][11][12][13][14][15]. In autopsy studies, fixation of the colon and careful use of a magnifying glass allow detection of small polyps that are more readily missed during colonoscopy [16][17][18][19][20].More than 90% of polyps detected at colonoscopy are epithelial in origin, that is, adenomas or hyperplastic polyps, and 75% of these are adenomas [8][9][10][11][12][13]. In the case of diminutive epithelial polyps (less than 5 mm), about half are hyperplastic [14,15].Age is the major determinant of adenoma prevalence [6,7]. Size at detection also increases with age [20]. Colorectal adenomas are uncommon in patients younger than 30 years of age. Anatomical distributionStudies show that colorectal adenomas are more common in the distal colon and rectum, similar to the distribution of colorectal cancer (see Chapter 63). Distribution, however, relates to size. Small adenomas are more uniformly distributed throughout the entire colon, whereas large adenomas (greater than 1 cm) show a distal predominance [7,8,21,22].

Role of the BK channel (KCa1.1) during activation of electrogenic K+ secretion in guinea pig distal colon

“…Massive losses occur during invasion by virulent bacteria as with cholera (12,63,78) or with some types of villous adenomas (11,46), but subtler imbalances over time also can lead to severe hypokalemia. Central to the regulation of luminal composition is the range of relative K ϩ and Cl Ϫ secretory rates possible with various secretagogues (64,87).…”

Is the distal hyperplastic polyp a marker for proximal neoplasia?

“…Colorectal polypoid lesions are classified into 3 groups: neoplastic polyps, which consist of adenomatous polyps and adenocarcinomas; non‐neoplastic polyps, which include hyperplastic and inflammatory polyps as well as hamartomas; and submucosal lesions, such as lipomas and lymphoid aggregates 1 . Adenomatous polyps (or adenomas) are further categorized as tubular, tubulovillous, or villous based on histology.…”

Cyclooxygenase-2 Expression in Human Colorectal Cancer Is Unrelated to Overall Patient Survival

“…3). Most colorectal tumors arise from precursor adenomatous polyps that develop into invasive adenocarcinoma, typically over a 5-to 10-year or longer period, and only about 10% of all adenomas proceed to cancer (4). Despite of the recognition of the adenoma-to-carcinoma transition in the pathogenesis of colorectal cancer, the etiology of this cancer remains unknown (5).…”