Colon polyps are growths in the lining of the colon. They can be small or large, flat or on a stalk. Most are benign (not cancerous), but some can contain cancer or grow into cancer. Colorectal cancer is diagnosed in approximately 5,000 people in the Chicago area each year.
Risk factors for colon polyps
- Age: becomes a concern after age 50 (age 45 in African-Americans)
- Genetics: problematic polyps run in families. In these cases, adenomas or colon cancer may develop at a young age. Of genetic syndromes include familial adenomatous polyposis, HNPCC (called Lynch Syndrome), and Peutz-Jeghers syndrome
- Personal history of colon polyps or cancer
- Diets: high fat and red meat intake, and low fruit/vegetable intake may increase risk
- Cigarette smoking, excessive alcohol consumption
- Obesity and sedentary lifestyle
Colon polyp types
There are two common types: hyperplastic and adenoma. The hyperplastic type is essentially not at risk for cancer. Adenoma is thought to be the root of almost all colon cancer (although only a minority of adenomas become cancer). Adenomas, especially large ones, can develop dysplasia – abnormal growth patterns which can lead down the path to cancer. That is why all adenomas should be removed – polypectomy (removal) prevent cancer. Because benign polyps and adenomas usually look the same, all should be removed and examined under a microscope by a pathologist.
Colon polyp symptoms
Larger polyps can cause blood in the stool (sometimes microscopic), but this is not reliably true. A positive HemOccult test requires further investigation. Anemia, or low blood count, is another sign. In most cases, there are no symptoms at all. This is why screening – which is examining people who have no symptoms – is important.
Screening for colon cancer
For age recommendations and frequency of repeat screening, see Screening for colon cancer.
A number of screening test are available. These differ in how much preparation is needed, and they also differ in effectiveness. Some tests for finding colon cancer are:
- Computed tomography (CT) colonography: a CAT scan. This requires a bowel preparation first. If polyps are suspected, a colonoscopy is needed. There is some radiation exposure.
- Colonoscopy: can find polyps, but is the only test that can also remove them, so that they don’t grow into cancer. It requires a bowel preparation.
- Stool tests: the US Preventive Services Task Force (USPSTF) considers them inferior in sensitivity, and a colonoscopy needs to be performed if there is a positive result. A bowel preparation is not needed.
Colonoscopy is not a perfect test, but it is very accurate, and it is the only screening test that also removes polyps at the same time. For this reason, the American College of Gastroenterology (ACG) calls colonoscopy a ‘Prevention Test’ and calls the others ‘Detection Tests’. Colonoscopy has the highest recommendation for colon cancer screening from the USPSTF and from the ACG. Colonoscopy should be performed by a gastroenterologist.
Treatment of colon polyps
Polypectomy (removal) is performed during colonoscopy using tools such as forceps, snares, or sometimes more complex techniques. If needed, the area can be marked with ink (called tattooing) to make it easy to find during surgery. At times, complex polypectomies may require multiple procedures or surgery. There is a risk of complications, although these are not common. Bleeding can occur days afterward. A perforation (tear) can occur at the removal site, which may require surgery to repair. An adenoma can grow back at the site of removal. Other uncommon risks can be discussed with a gastroenterologist.
Once an adenoma is found, the odds are higher that more will be found in the future. Anyone with a history of adenoma should have more frequent colonoscopies. The time interval until the next procedure depends on the quality of the colon cleansing, how many polyps were found and removed, how large they were, whether any were flat, and the microscopic findings on pathology.