A colorectal polyp (adenoma) is an abnormal growth of tissue on the inside lining of the colon or rectum.
Colorectal polyps are quite common, occurring in about 25% of adults who are 50 years of age and older. They are most often benign, or noncancerous. However, polyps can sometimes develop into colorectal cancer.
Most often, polyps cause no symptoms at all. They are found when a healthcare professional examines the colon. Rarely, polyps can cause blood in the stools or abdominal distress.
The exact cause of polyps is not well understood. Sometimes polyps are genetic and occur more commonly in multiple generations of a family (high-risk familial syndromes). Polyps are more common as a person gets older. Diets high in fat and low in fiber are thought to play a role in causing polyps. Alcohol use, cigarette smoking, and obesity may also increase the risk of developing polyps.
Currently, no definite way is known to reduce the risk of polyps. Diets high in fiber, folic acid and calcium, and low in fat or calcium supplements (with or without Vitamin D) may help to reduce the risk. Nonsteroidal anti-inflammatory medications may also reduce the risk of developing colorectal polyps in people in high-risk families.
Colorectal polyps can be seen only with special tests because polyps are hidden within the body.
Starting at the age of 40 (or earlier for those with a positive family history of colon cancer or polyps), people should have yearly digital rectal exams and stool testing for occult blood. Annual fecal occult blood tests allow early detection of colorectal polyps. Most importantly, the polyps can then be removed before they become colorectal cancer.
Beginning at the age of 50, a flexible sigmoidoscopy should be done every 5 years. A sigmoidoscopy is a procedure that allows a healthcare professional with special training to look into the rectum and sigmoid colon through a flexible scope. This scope, however, is not long enough to allow examination of the upper portion of the colon.
A colonoscopy is the preferred test to examine the entire colon and rectum. Like a sigmoidoscopy, this procedure allows a physician to look into the rectum and sigmoid colon through a flexible scope. However, a colonoscopy is performed with a longer instrument, allowing the examiner to look further or deeper into the bowel than in sigmoidoscopy.
Colonoscopy should be repeated every 10 years for an individual at average risk, whose preceding examination was normal. Colonoscopy should be repeated every 3 to 5 years for those with a history of colon polyps or cancer.
A barium enema is a special X-ray test that can detect polyps, although it may be less sensitive than colonoscopy. A double-contrast barium enema should be performed every 5 years. Some people may prefer the barium enema to colonoscopy.
One of the newest options to evaluate the colon for adenomas is called Virtual Colonscopy. This test uses imaging techniques to evaluate the entire colon, but there is controversy concerning the accuracy of this option.
The main importance of colorectal polyps is that they may become colorectal cancer. Occasionally, a polyp actually is a small, early cancer.
Colorectal polyps are not contagious and pose no risk to others.
Detection of and removal of precancerous colorectal polyps can prevent or significantly reduce the risk of development of cancers from these polyps. When polyps are seen with a barium enema X-ray test, the person may need a sigmoidoscopy or colonoscopy.
During these procedures, the healthcare professional can sometimes remove or destroy polyps through the tube or cut off a small piece of the polyp for a biopsy to be looked at under a microscope. In some cases, a portion of the colon is removed surgically, with a colostomy. This is usually done if the polyp is large, or if the biopsy looks suspicious under the microscope.
Colonoscopy and sigmoidoscopy involve a very low risk of tearing a hole in the bowel, bleeding, and infection. This risk is increased when biopsies are taken. Surgery can be complicated by infection, bleeding, or an allergic reaction to anesthetic.
After a polyp is treated, the person can generally go back to his or her normal activities. The healthcare professional will recommend a follow-up plan based on the type of polyps a person has.
All persons are advised to have regular screening for colorectal polyps and colorectal cancer after the age of 50. Those with polyps will need more frequent future screenings with either colonoscopy or barium enema.
Gastrointestinal and Liver Disease, 1998, Sleisenger et al