THE SIGNIFICANCE OF POLYPS The presence of polyps in the colon raises many questions for patients. What is the significance of finding a polyp? Does this mean that I have, or will develop, colon cancer? Will finding a polyp require colon surgery?
Some types of polyps (the ones known as "adenomas") have the potential to turn into colon cancer while others (such as "hyperplastic" or "inflammatory" polyps) have virtually no chance to develop into a cancer. You should not worry if polyps are found on your examination since:
It is very important that you follow-up with your doctor, since the type, size, and location of the polyps and the way in which they were removed are relevant for determining the best course of action for you. Most people who have had adenomas removed will require repeated examinations in the future to be sure that all the adenomas have been found and that new adenomas have not developed.
WHAT CAUSES POLYPS? Polyps are very common in men and women of all races who live in industrialized countries, which suggests that dietary and environmental factors are important in their development. Although the exact dietary and environmental factors are not completely understood, some of the known risk factors appear to be:
Colorectal cancer is uncommon before age 40. Ninety percent of cases occur after age 50, with men and women being equally affected; therefore, screening for polyps usually begins at 50 for both sexes. It takes approximately 10 years in the average person for a small polyp to grow and become a cancerous polyp.
Polyps and colon cancer tend to run in families, which suggests that genetic factors are also important in their development. Intensive research on the genetic basis of colon cancer is ongoing. Rare genetic diseases associated with multiple colon polyps and early colon cancer (called "familial adenomatous polyposis") have been identified. A number of other genetic mutations have been found that are associated with an increased risk of developing polyps and colon cancer. Most common is Hereditary Non-Polyposis Colon Cancer (HNPCC), which also results in a high risk of colon cancer, often beginning in the 20s and 30s, but without an unusual number of polyps. Testing for these genes may have a role in families with unusual rates of colorectal cancer, but not in the general population.
It is very important that you tell your doctor if there is a history of colon polyps, colon cancer, or other forms of cancer in your family, particularly if cancers developed at an early age or multiple, different types of cancers developed. You may also be at increased risk if your close relatives have been diagnosed with colon polyps, colon cancer, or other forms of cancer. As a general rule, screening for colon cancer begins at an earlier age in people with a family history of cancer or polyps. These issues should be discussed with your doctor.
HOW ARE POLYPS FOUND? Polyps are usually found on flexible sigmoidoscopy or colonoscopy examinations. They can also be detected on a barium enema x-ray, although small polyps are less often seen on x-ray and they cannot be removed with x-ray. Colonoscopy is the most effective examination because it gives direct visualization of the entire colon and allows the doctor to remove polyps for laboratory analysis.
WHAT DO POLYPS LOOK LIKE? During colonoscopy, your doctor inserts a very thin flexible tube with a light source and small camera into the large intestine (colon) and examines the lining of the colon. The inside of the colon is a tube-like structure with a flat surface with curved folds. A polyp will appear like a lump that protrudes into the inside of the colon. The tissue covering a polyp may look the same as normal colon tissue, or, there may be tissue changes ranging from subtle color changes to ulceration and bleeding. A polyp can have a flat base against the lumen (sessile) or can extend out on a stalk (pedunculated).
WHY REMOVE POLYPS? Colorectal cancer is the second leading cause of cancer deaths in the United States, accounting for 14 percent of cancer deaths. Colorectal cancer is preventable if precancerous polyps (ie, adenomas) are detected and removed before they become malignant. Over time, some small polyps can change their tissue structure and grow in size to become cancerous polyps. Polyps are removed when they are found on colonoscopy to eliminate the potential for them to become malignant.
DO POLYPS CAUSE SYMPTOMS? Polyps do not usually produce symptoms. They are most commonly detected during routine screening examinations (such as flexible sigmoidoscopy or colonoscopy). Polyps are sometimes suspected when there are traces of blood in the stool or when patients have a low blood count (anemia), which is usually due to very small amounts of bleeding from the polyps for many years. These small amounts of blood are typically detected when doctors test stool samples using special cards that have been impregnated with a dye that reacts with blood (called fecal occult blood testing). Uncommonly, polyps can cause visible blood in the stool if they ulcerate and bleed. Rarely, very large polyps can cause a blockage in the colon that will cause abdominal pain.
TYPES OF POLYPS The two most common types of polyps found during colonoscopy are:
Other types of polyps can also be found in the colon, but are far less common and will not be discussed here.
Hyperplastic Hyperplastic polyps are usually small, located in the end-portion of the colon (the rectum and sigmoid colon), have no potential to become malignant, and are of no clinical significance. Because they can not always be distinguished by their appearance from other types of polyps, they are often removed or biopsied for tissue analysis.
Adenomatous Two-thirds of colon polyps are adenomas (hence the polyp is termed "adenomatous"). These polyps have the potential to become malignant. Adenomas are classified by their size, general appearance, and their specific features as seen under the microscope. As a general rule, the larger the adenoma, the more likely it is to eventually become a cancer. In addition, large adenomas may already have cancer contained within them. As a result, your doctor will usually try to biopsy (obtain a sample) or remove the polyp so that it can be examined under the microscope.
HOW ARE POLYPS REMOVED? The medical term for removing polyps is "polypectomy." Small polyps can be removed by an instrument called a biopsy forceps, which snips off small pieces of tissue. Larger polyps are usually removed by putting a noose, or snare, around the polyp base and burning through the tissue with electric cautery. Neither of these procedures is painful,and you will usually not be aware that they are being done. Rarely will a polyp be too large to remove by colonoscopy and require surgery for removal.
Polypectomy is very safe, but all procedures entail some risks, which you should discuss with your doctor. The most common complications of polypectomy include bleeding and perforation (creating a hole in the colon). Fortunately, although these are the most common complications of polypectomy, they are still infrequent. Bleeding can usually be controlled by colonoscopy, during which the bleeding site is cauterized, although surgery is sometimes required. Surgery is usually required for perforation. Other complications have been described but occur much less frequently.
You should follow your doctor's instructions carefully following polypectomy by not taking drugs known to promote bleeding (such as aspirin, Advil, and other pain relievers, which are blood thinning medications). In addition, you should follow your doctor's instructions about finding out the results of the tissue analysis of your polyps and when a repeat examination should be performed.
CAN POLYPS COME BACK? A person who has had an adenomatous polyp removed is at increased risk for developing more polyps, which will also most likely be adenomatous. There is a 25 to 30 percent chance that adenomas will be present on a repeat colonoscopy done three years after initial polypectomy. Some of these polyps were probably present on the original examination, but may have been too small to detect while others are new.
After polyps are removed, your doctor will recommend repeat colonoscopies for surveillance. The recommended interval between colonoscopies is usually three to five years, but depends upon several factors:
IS THERE ANY WAY I CAN BE SCREENED FOR POLYPS WITHOUT HAVING TO GO THROUGH ANOTHER COLONOSCOPY? Colonoscopy will remain the best examination for follow-up with patients who have had polyps removed. Although new technologies are being developed that show promise for detecting polyps (including molecular genetic tests and "virtual colonoscopy" using CT or MRI technology), colonoscopy will remain the most efficient means for the foreseeable future.
WHAT CAN I DO TO REDUCE THE CHANCE OF GETTING MORE POLYPS OR COLON CANCER ? The most important thing to do to reduce the likelihood of developing colon cancer is to follow your doctor's instructions regarding future screening examinations. People who undergo screening for colon cancer are much less likely to die from colon cancer.
Intensive research is ongoing to develop ways to prevent polyps and colon cancer with diet or with medications. A number of nutrients and medications have been identified that may reduce the risk of colon cancer. Guidelines issued by one of the major medical societies in the United States (the American College of Gastroenterology) suggest the following to prevent polyps:
Other measures may be effective, such as nonsteroidal antiinflammatory drugs (NSAIDs), folic acid, or selenium supplementation.
IMPLICATIONS FOR MY FAMILY First-degree relatives (a parent, brother, sister, or child) of a person who has been diagnosed with an adenomatous polyp (or colorectal cancer) at a young age (before the age of 50 years) are at increased risk for adenomatous polyps and colorectal cancer compared to the general population. Thus, it is important that the above family members should be made aware if you have been diagnosed with an adenoma (or colon cancer). While screening for polyps and cancer is recommended for all people at risk (typically beginning at age 50), those at increased risk should begin screening earlier, typically at age 40. Some conditions (such as "hereditary nonpolyposis colorectal cancer" and "familial adenomatous polyposis") are associated with an even higher risk of colonic polyps or cancer in family members, warranting a more aggressive approach to screening family members. You should discuss these issues with your doctor.