- A colonic polyp is an intraluminal outgrowth arising from the large intestinal epithelial lining, which is usually benign. The potential for malignant transformation necessitates close evaluation and monitoring. (See Colorectal Malignancy.)
- 3 types:
- Adenomatous: May become malignant:
- Villous: Polyps tend to be larger, most likely to become malignant (10%)
- Tubular (75%)
- Tubulovillous (15%)
- Hyperplastic: Rarely become malignant
- Inflammatory: No malignant potential
- Adenomatous: May become malignant:
- Varies considerably worldwide. Industrialized countries are generally at greater risk compared to the rest of the world.
- Age is an important determinant in the US and other high-risk countries.
- Adenomas more common in men than women
- Estimated 5% of the US population
- ∼20% of middle-aged and older adults
- 50% seen in ≥50 years
Average prevalence of 25% before age 40 to as high as 55% at age 80
- Advancing age
- Family history of polyposis, polyps, or colorectal cancer (CRC)
- Inflammatory bowel disease
- Current cigarette smoking
- Excessive alcohol intake: >8 drinks of beer or spirits a week (1)
- Sedentary lifestyle
May occur in the setting of genetic syndromes that are associated with gene mutations
- Diet: High-fiber diet has been a controversial risk. Two recent studies stressed that doubling fiber intake can significantly reduce colorectal cancer risk (2,3).
- Avoid smoking.
- Limit alcohol intake.
- Calcium supplement: Shown reduction of colorectal adenoma recurrence (4)
- Vitamin D, folic acid, vitamin B6
- Aspirin. Three randomized controlled trials (RCT) revealed that ASA caused significant reduction in the recurrence of sporadic adenomatous polyps after 1 to 3 years while short-term studies support regression of colorectal adenomas in FAP (5).
- Adenomatous polyps: Formed from abnormal proliferation and from dysplasia
- Nonadenomatous polyps: Result from abnormal mucosal maturation, inflammation, or architecture
Unknown. May be related to environmental and genetic factors.
Commonly Associated Conditions
Associated with several hereditary disorders:
- Familial adenomatous polyposis (FAP)
- Peutz-Jeghers syndrome
- Gardner syndrome
- Hereditary nonpolyposis colon cancer (HNPCC)
- Diarrhea or constipation
- Abdominal pain
- Usually normal
- Rectal lesions may be felt by digital examination.
Diagnostic Tests & Interpretation
Initial lab tests
- Complete blood count (CBC): Anemia
- Electrolyte abnormalities: In villous adenoma
- Colonoscopy (6): Standard of goal. Most sensitive test available but its sensitivity is a concern. Chromoscopy enhances the detection of neoplastic lesions in the colon and the rectum (7).
- Chromoscopy: Studies are examining narrow-band imaging for histologic differentiation between adenomatous and hyperplastic polyps (7,8).
- CT colonography (formerly known “Virtual colonoscopy”)
- Air-contrast barium enema: Misses small lesions
- Fecal occult blood test (FOBT): Many false positive results
- Fecal DNA testing
- Some polyps are more likely to become malignant, hence, they require histopathologic evaluation.
- Villous adenoma:
- Gross: Velvety, multiple-frond projections
- Micro: Glands proliferate in fingerlike projections, malignant degenerations
- Tubular adenoma:
- Gross: Smooth, firm, pink surface; microlobulated; fissures; pedunculated
- Glands proliferate in tubular fashion, nuclei elongated, hyperchromatic
- Endoscopic polypectomy: Major risks include perforation and bleeding
- Colonic resection: For multiple intestinal polyps associated with FAP
Benign polyps should have follow-up colonoscopy every 3–5 years.
Offer CRC screening for average risk patients beginning at age 50, earlier for at-risk patients. Most guidelines recommend to stop screening if life expectancy is less than 10 years.
Calcium supplementation might contribute a moderate degree to the prevention of colorectal adenomatous polyps (4).
- Curable with polypectomy
- Projection estimates suggested that 50% of postpolypectomy patients will have a recurrence within 7.6 years; hence, need follow-up (9).
- Adenomatous polyps may undergo malignant transformation if not removed.
- Multiple polyps are particularly at increased risk of developing colorectal cancer.
Perforation with colonoscopy is rare.
1. Anderson JC, Alpern Z, Sethi G, et al. Prevalence and risk of colorectal neoplasia in consumers of alcohol in a screening population. Am J Gastroenterol. 2005;100:2049–55.
2. Asano TK, McLeod RS. Dietary fibre for the prevention of colorectal adenomas and carcinomas. Cochrane Database of Systematic Reviews. 2002, Issue 1. Art. No.: CD003430. DOI:10.1002/14651858.CD003430.
3. Peters, Ulrike, et al. “Dietary fibre and colorectal adenoma in a colorectal cancer early detection programme.” Lancet. 361.9368 (2003):1491–5.
4. Weingarten MA, Zalmanovici A, Yaphe J. Dietary calcium supplementation for preventing colorectal cancer and adenomatous polyps. Cochrane Database Syst Rev. 2008:CD003548.
5. Asano T, McLeod R. Non steroidal anti-inflammatory drugs (NSAID) and aspirin for preventing colorectal adenomas and carcinomas Cochrane Database of Systematic Reviews.2010;2:CD004079.
6. Kim DH, Pickhardt PJ, Taylor AJ, et al. CT colonography versus colonoscopy for the detection of advanced neoplasia. N Engl J Med. 2007;357:1403–12.
7. Brown SR, et al. Chromoscopy versus conventional endoscopy for the detection of polyps in the colon and rectum. Cochrane Database Syst Rev. 2007;4:CD006439. DOI:10.1002/14651858.CD006439.pub2.
8. Rastogi, Amit, et al. “Recognition of surface mucosal and vascular patterns of colon polyps by using narrow-band imaging: interobserver and intraobserver agreement and prediction of polyp histology.” Gastrointestinal endoscopy. 2009;69(Suppl 3):716–22.
9. Yood, Marianne Ulcickas, et al. “Colon polyp recurrence in a managed care population.” Archives of internal medicine. 163.4 (2003):422–6.
Elwood PC, Gallagher AM, Duthie GG, et al. Aspirin, salicylates, and cancer. Lancet. 2009;373:1301–9.
11. Kumar D, et al. Pathologic Basis of Disease, 7th ed. 2005;856–870.
12. Larsen IK, Grotmol T, Almendingen K, et al. Lifestyle as a predictor for colonic neoplasia in asymptomatic individuals. BMC Gastroenterol. 2006;6:5.
13. Seong-Eun K, et al. An association between obesity and the prevalence of colonic adenoma according to age and gender. J Gastroenterol. 2007;42(8).
See Also (Topic, Algorithm, Electronic Media Element)
Algorithm: Bleeding, GI
211.3 Benign neoplasm of colon
68496003 Polyp of colon (disorder)
- Villous adenomatous polyps are the “villains” (most likely to become malignant).
- Hyperplastic polyps rarely become cancer.
- Up to 50% of patients who have polyps removed have recurrent polyps.