Bowel polyps are small growths that develop on the lining of the colon or rectum. They are common, and most are not cancerous. However, some types, including adenomatous polyps, can develop into bowel cancer over time.
Doctors may also call them colon polyps, colorectal polyps or rectal polyps. The cancer risk depends on the type, size, number and microscopic features of the polyp.
Bowel polyps at a glance
- Most bowel polyps are benign.
- Many cause no symptoms, and doctors discover them during colonoscopy or screening.
- Some adenomas and serrated polyps can become cancerous over time.
- Doctors usually remove polyps during colonoscopy.
- A laboratory examines the removed tissue.
- Some people need surveillance colonoscopy after polyp removal.
What are bowel polyps?
Bowel polyps are abnormal growths that arise from the inner lining of the large bowel. They can be flat, slightly raised or attached to the bowel wall by a stalk.
Polyps vary greatly in size. Some are only a few millimetres across, while others are much larger.
NHS guidance explains that bowel polyps are very common and are not usually serious. However, a small proportion can become cancerous over many years. For this reason, doctors often remove them when they find them.
Do bowel polyps cause symptoms?
Most bowel polyps do not cause symptoms. Many people only discover they have a polyp during colonoscopy or bowel cancer screening.
Larger polyps can occasionally cause symptoms such as:
- Blood or mucus in the stool.
- Bleeding from the back passage.
- A persistent change in bowel habit.
- Diarrhoea or constipation.
- Unexplained weight loss.
These symptoms do not prove that a polyp is present. They can occur with many other bowel conditions, including bowel cancer, haemorrhoids and inflammatory bowel disease.
Read our guide to bowel cancer symptoms and warning signs.
Can bowel polyps turn into cancer?
Some can. However, most bowel polyps never become cancerous.
The classic pathway involves certain adenomatous polyps, also called adenomas. Over time, some adenomas can accumulate cellular changes that eventually lead to colorectal cancer.
Some serrated polyps can also carry cancer risk, particularly when they are larger or show dysplasia.
This progression usually takes years rather than days or weeks. Removing precancerous polyps is one of the reasons colorectal screening and colonoscopy can reduce future bowel cancer risk.
Which bowel polyps have a higher cancer risk?
The risk is not the same for every polyp. Doctors assess several features after removal.
| Feature | Why it matters |
|---|---|
| Polyp type | Adenomas and some serrated polyps can have precancerous potential. |
| Size | Larger polyps are more likely to contain advanced changes. |
| Number | Multiple polyps can affect follow-up recommendations. |
| Dysplasia | Higher-grade cellular changes can indicate greater risk. |
| Complete removal | Doctors need to know whether the lesion was fully removed. |
| Histology | Microscopic examination helps classify the polyp and guide surveillance. |
Recent prospective research found that people with high-risk adenomas or high-risk serrated polyps had a higher subsequent risk of colorectal cancer than people whose first colonoscopy found no polyps. Surveillance colonoscopy was also associated with a lower later colorectal cancer risk in that cohort.
What are adenomatous polyps?
Adenomatous polyps, or adenomas, are one of the main types of precancerous colorectal polyps.
Not every adenoma develops into cancer. In fact, most do not. However, advanced adenomas have a higher future cancer risk than small, low-risk adenomas.
Pathologists may describe adenomas according to their architecture, size and degree of dysplasia. These features help the clinical team decide whether follow-up colonoscopy is necessary.
What are serrated polyps?
Serrated polyps are another group of colorectal polyps. Some have little clinical significance, while others can contribute to a separate pathway to colorectal cancer.
A 2024 systematic review and meta-analysis found that advanced serrated polyps, including larger lesions and lesions with dysplasia, were associated with a higher later colorectal cancer risk than non-advanced serrated polyps.
How doctors find bowel polyps
Doctors often find polyps during a colonoscopy. A colonoscope is a flexible tube with a camera that allows the endoscopist to inspect the inside of the colon and rectum.
CT colonography can also show larger polyps, although a conventional colonoscopy may still be needed to remove a lesion or take tissue for analysis.
Bowel cancer screening can also identify people who need further investigation. In England, the NHS bowel cancer screening programme uses FIT to look for microscopic blood in stool. A positive FIT does not prove that cancer or a polyp is present, but it can lead to further assessment.
Read how the FIT stool test works.
Read our guide to bowel cancer tests and colonoscopy.
How are bowel polyps removed?
Doctors usually remove bowel polyps during colonoscopy. This is called a polypectomy.
The endoscopist may use a wire snare or another technique to remove the lesion. Very large or complex polyps can sometimes require advanced endoscopic treatment or surgery.
After removal, the endoscopy team sends the tissue to a laboratory. A pathologist examines it to determine the type of polyp, whether dysplasia is present and whether the endoscopist removed the lesion completely.
If cancer is found within a removed polyp, the specialist team assesses whether additional treatment or surgery is needed.
Do all bowel polyps need follow-up colonoscopy?
No. Follow-up depends on the number, size and type of polyps, the quality of the colonoscopy and whether the lesions were completely removed.
People with higher-risk findings may need surveillance sooner than those with low-risk findings. Therefore, it is important to follow the interval recommended by the endoscopy or colorectal team rather than choosing a repeat colonoscopy schedule independently.
A 2024 systematic review found that surveillance colonoscopies are sometimes performed earlier than guideline-recommended intervals, highlighting the importance of risk-based follow-up rather than unnecessary frequent procedures.
Can removing bowel polyps prevent bowel cancer?
Removing precancerous polyps can reduce the chance that those particular lesions will progress to cancer.
This is one of the key purposes of colorectal screening and colonoscopy. However, removing a polyp does not mean a person can never develop another polyp or bowel cancer in the future.
That is why some people need surveillance after polypectomy, particularly when the original findings were higher risk.
What happens if cancer is found in a polyp?
Sometimes an apparently benign polyp contains an early cancer when the laboratory examines it.
The specialist team then reviews factors such as how deeply the cancer has invaded, whether the polyp was completely removed and whether the pathology shows features associated with a higher risk of spread.
Complete endoscopic removal may successfully treat some very early cancers. Others require bowel surgery and further staging tests.
Read our guide to bowel cancer treatment.
Risk factors for developing bowel polyps
The exact cause of an individual polyp is often unclear. However, NHS guidance lists several factors associated with a higher chance of bowel polyps.
- Increasing age.
- A family history of bowel polyps or bowel cancer.
- Inflammatory bowel disease, including ulcerative colitis and Crohn’s disease.
- Smoking.
- Being overweight.
Some inherited conditions can also cause multiple colorectal polyps and a much higher cancer risk. People with a suspected hereditary syndrome need specialist genetic and colorectal assessment.
Should bowel polyps be monitored rather than removed?
When an endoscopist can safely remove a polyp during colonoscopy, doctors usually prefer removal because it allows laboratory examination and removes a potential precursor lesion.
However, treatment decisions can differ for technically difficult lesions, people with major medical problems or lesions that require specialist endoscopic expertise. The endoscopy team will explain the safest approach.
Colon hydrotherapy and bowel polyps
Colon hydrotherapy does not remove bowel polyps, diagnose them or prevent a polyp from becoming cancerous.
If you have unexplained rectal bleeding, blood in your stool, persistent bowel changes or a known polyp that is awaiting investigation or removal, medical assessment takes priority over colon hydrotherapy.
At Parkland Natural Health in Holborn, every appointment includes consultation and suitability screening. If your symptoms or medical history indicate that further medical assessment is needed, we may advise you not to proceed until that assessment is complete.
After colonoscopy or polyp removal, follow the advice of your endoscopy team about recovery and when it is safe to resume non-medical bowel-wellbeing treatments.
For suitable clients without contraindications, colon hydrotherapy remains a separate bowel-wellbeing service and is not a substitute for colonoscopy, polypectomy or cancer surveillance.
Frequently asked questions about bowel polyps
Are bowel polyps cancer?
Usually not. Most bowel polyps are benign. However, some types can become cancerous over time, which is why doctors often remove them.
Do all colon polyps turn into cancer?
No. Most do not. Cancer risk varies according to the type, size, number and microscopic features of the polyp.
Can bowel polyps grow back?
A completely removed polyp does not usually grow back in the same way, but new polyps can develop elsewhere in the bowel. This is one reason some people need surveillance colonoscopy.
Can a FIT test detect bowel polyps?
FIT detects microscopic blood rather than polyps themselves. Some polyps bleed and may produce a positive FIT, while others do not. Colonoscopy is the test that directly visualises the bowel lining and allows polyps to be removed.
Can a bowel polyp cause pain?
Most polyps cause no symptoms. Larger polyps can occasionally cause bleeding, mucus or bowel-habit changes, but pain is not a reliable way to identify a polyp.
Trusted medical and scientific sources
- NHS: Bowel polyps
- PubMed: Risk after conventional adenomas and serrated polyps
- PubMed: Serrated polyps and later colorectal cancer risk
- PubMed: Surveillance colonoscopy after adenomatous polyps
- PubMed: Colon polyp surveillance review
Medical information notice: This article provides general educational information. Bowel polyps require appropriate medical assessment, and follow-up depends on individual colonoscopy and pathology findings.
