A colon polyp is a small growth of tissue that projects from the lining of a section of the large intestine known as the colon.
Polyps are common and increasingly so as people age. Colorectal polyps, which are polyps in the colon or rectum, are estimated to occur in at least 30 percent of adults who are 50 years old or more in the United States.
Colorectal polyps also occur in children with an estimated 6 percent affected, rising to 12 percent in those who experience intestinal bleeding.
In this article, we take a close look at colon polyps, including their causes, treatments, and how to prevent them from occurring.
Different types of polyps carry different risk factors. Furthermore, the size of the polyp is related to its potential severity.
A 2014 review concluded that polyps of 5 millimeters (mm) or less had little risk of becoming cancerous while those between 1.5 and 3.5 centimeters (cm) had a malignancy potential of 19 to 43 percent.
The most common types of polyps are hyperplastic and adenomatous polyps:
Hyperplastic polyps, or inflammatory polyps, are usually harmless and not a cause for concern with a low malignancy potential. These polyps will rarely become cancerous.
Adenomas, or adenomatous polyps, are not cancerous but they may become cancerous in the future. Larger adenomas are more likely to become cancerous. Doctors usually recommend removing adenomas.
Malignant polyps are polyps that contain cancerous cells. The best treatment for these polyps will depend on the severity of the cancer and a person's overall health.
People with colon polyps often have no signs or symptoms of the condition.
Doctors usually find these polyps during routine tests or tests for another disorder. A doctor may recommend that older adults and people with risk factors for colon polyps have regular screening. When doctors detect polyps early, there is a better chance that they can completely remove the growths without complications.
When colon polyps do cause symptoms, people may notice the following:
- Bleeding from the rectum. This is the most common symptom of polyps, although it can also be a sign of other conditions, such as hemorrhoids or minor tears in the anus.
- Abdominal pain. Large polyps that partially block the bowel can cause abdominal cramps and pain.
- A change in the color of stools. Minor polyp bleeding can cause red stripes in the stool, and heavier bleeding can make the stool appear black. However, other factors can also change the color of the stool, such as foods, medicines, and supplements.
- Iron deficiency anemia. If a person's polyps bleed slowly over time, they may develop an iron deficiency. Anemia can cause weakness, pale skin, shortness of breath, light-headedness or fainting.
- A change in bowel habits that lasts longer than a week, including constipation or diarrhea.
People are either born with colon polyps or develop them during their lifetimes.
Doctors do not yet know the exact causes of colon polyps, but their appearance may be linked to the following lifestyle factors:
- a high-fat diet
- eating lots of red meat
- not eating enough fiber
- smoking cigarettes
In some people, genetic factors cause the cells of the colon to multiply more than they should. When this happens in the colon, people get colon polyps. When it occurs in the rectum, people get colorectal polyps.
People are more likely to develop colon polyps if they have the following inherited conditions:
- familial adenomatous polyposis (FAP)
- Gardner syndrome
- Peutz-Jeghers syndrome
People with these conditions have an increased risk of developing cancer in several organs, including the small intestine and colon.
Certain risk factors make a person more likely to develop colon polyps. These include:
- lack of exercise
- smoking cigarettes
- drinking alcohol
- inflammatory bowel diseases (IBD), such as ulcerative colitis or Crohn's disease
- a family history of colon polyps
- uncontrolled type 2 diabetes
- African-American heritage, as this increases the risk of colon cancer
A doctor may recommend that older adults and people with risk factors for colon polyps have regular screening exams, especially after 50 years of age.
A doctor may begin by taking a person's medical history, assessing risk factors, and performing a physical exam. If they suspect colon polyps, they may recommend further tests. Catching colon polyps early can reduce the risk of complications.
Screening exams may include:
- Colonoscopy. During a colonoscopy, the doctor inserts an illuminated camera tube called an colonoscope into the anus to examine the colon. They may then remove any polyps or take a biopsy, which is where a tissue sample is removed and send to a lab for examination under a microscope.
- Flexible sigmoidoscopy. A shorter version of a colonoscope called a sigmoidoscope is used to examine a limited portion of the colon. If the doctor finds polyps, they will need to perform a colonoscopy to remove them.
- Virtual colonoscopy. This is a noninvasive procedure where a doctor uses imaging methods to examine the colon. These may include X-rays, CT scans, or MRI scans. These tests may be less sensitive than colonoscopic tests. A person may have to swallow a barium solution to make the X-ray images clearer.
- Stool exam. Doctors may also look for the presence of blood in stools or examine the stool DNA. Depending on the results, they may then perform a colonoscopy to investigate further.
Doctors will usually treat colon polyps by removing them. They may also suggest certain lifestyle changes to prevent colon polyps from reoccurring.
Doctors can remove colon polyps using the following methods:
- Colonoscopy. Doctors can use a cutting instrument or an electrified wire loop on the end of a colonoscope to perform a polypectomy, or polyp removal. For smaller polyps, doctors may inject a liquid underneath the polyp to raise and isolate it from the surrounding area for easier removal.
- Laparoscopy. During a laparoscopy, the doctor will make a small incision into the abdomen or pelvis and insert an instrument called a laparoscope into the bowel. They use this technique to remove polyps that are too large or cannot be removed safely by colonoscopy.
- Removing the colon and rectum. This procedure, known as a total proctocolectomy, is only necessary when a person has a severe condition or cancer. Doctors recommend this option for those with rare inherited conditions, such as familial adenomatous polyposis (FAP). FAP is an inherited condition that causes cancer of the colon and rectum, and polyp removal may prevent cancer from developing.
After removing a polyp, the doctor will send it for lab testing where experts will check it for cancer.
A pathologist who is a specialist in analyzing tissue samples will examine the polyp tissue under a microscope and check whether it is benign or precancerous. The will base the recommended time interval for the next colonoscopy on this information plus the number and size of polyps.
In people who already have polyps or colon cancer, the doctor may prescribe aspirin and coxibs (COX-2 inhibitors) to stop new polyps from forming. For people with a family history of colon polyps, genetic counseling is recommended to prevent their development.
People can reduce their risk of developing colon polyps by adopting healthy lifestyle habits, such as:
- eating a low-fat diet
- eating a diet high in fruits, vegetables, and fiber
- keeping a normal body weight
- quitting or avoiding cigarette smoking
- avoid excessive alcohol use
People who have had colon polyps should get regular colon checkups, as they have a higher likelihood of developing others.
A polyp is a growth of tissue on the lining of the colon and rectum that projects into the intestines.
People with colon polyps usually have no symptoms. Most colon polyps are harmless, though some types can become cancerous. Polyp removal is the best way to treat colon polyps and prevent cancer from developing.
People with risk factors should get regular screenings for colon polyps, especially if they are over 50 years of age.
If a person has polyps, they should follow their doctor's advice about getting checkups and making lifestyle changes to help manage the condition.