Colonic Polyps
In this article
What is a polyp?
A polyp is an overgrowth of the cells in the inner lining of the bowel wall. Colon is a very common place for polyps. One in four people over 50y will develop at least one colonic polyp. There are various types polyps and the effects of the differ according to the type. Some people develop one or few polyp while others may have more and the effects differ when the number of polyps change. Polyps are very significant because, if they are left, some may become a cancer in the colon or rectum. Equally if detected early and treated, can prevent a cancer!
What are the various types of polyps?
Inflammatory Polyps
In conditions with overt inflammatory activity Eg: Ulcerative Colitis / Crohn’s. disease. Thought to occur due to lymphoid tissue / MALT (mucosa-associated lymphoid tissue) hyperplasia
Hyperplastic Colorectal Polyps
Commonly though that there is no malignant potential especially if only few and mostly on the left side. They are usually serrated polyps and have a malignant potential if found on the right side or if found in higher numbers as in Hyerplastic Polyposis Syndrome (which is when there are more than 5 polyps proximal to the sigmoid with two of them bigger than 10mm in diameter; or any number proximal to the sigmoid with a first degree relative who has Hyerplastic Polyposis Syndrome or having more than 30 hyperplastic polyps of any size).
Hamartomatous Colorectal Polyps
Normal cells with faulty development / arrangement. Grow at the normal rate of the host tissue Eg: Juvenile polyp. If multiple or Syndromic, have an elevated malignant potential. Juvenile Polyposis Syndrome (JPS) 40-60%. Peutz-Jeghers Syndrome (PJS) 40-60%. PTEN Hamartomatous Tumor Syndrome (PHTS) with either Cowden (CS) or Bannayan-Riley-Ruvalcaba syndromes (BRRS) 18%.
Neoplastic Colorectal Polyps
Adenomatous polyps, DALM (Dysplasia Associated Lesions / Mass) and colorectal cancer are neoplastic polyps. Adenomatous polyps & DALM are thought to be early stages of developing colorectal cancer. Adenomatous polyps are the most commonest in this group and most significant.
Adenomatous Polyps
A tumour of glandular tissue. Exponential growth rate and malignant risk (1% [1cm] 10% [2cm] 50% ). Mainly four subtypes according to the cellular arrangement: Tubular Adenoma (5% cancer risk), Tubular-villous Adenoma (20% cancer risk), Villous Adenoma (40% cancer risk) and Serrated Adenoma (Significant cancer risk). Overall, if left untreated, about 1 in 10 will change and become a cancer.
Dysplasia Associated Lesions / Masses
They develop in the background of Inflammatory Bowel Disease due to chronic inflammation related DNA damage. They have a cancer risk of 20 - 40%.
Why do polyps develop?
It is not completely known why polyps develop. However there is some understanding on who will have a higher chance to develop polyps. Certainly the risk increases with age. Some have a genetic predisposition which means it depends on your genes to some degree. Some lifestyles have a higher risk.
Who has a higher risk of developing colonic polyps?
- Over 50 years of age
- If you had polyps before
- Someone in your family has had polyps, polyposis syndromes or cancer of the large bowel
- If eat a lot of fatty foods
- Smoking
- Drinking alcohol
- Do not take regular exercise
- Overweight
What are the symptoms of polyps?
Most people are unaware of having polyps as they often produce no symptoms. Some polyps can however produce a small amount of bleeding or an excess production of mucus (slime) with bowel motions. A change in bowel habit may occur and very large polyps may lead to a blockage in the bowel but this is extremely rare.
Treatment for polyps
Polyps are generally removed at the time of your colonoscopy. There are several methods for doing this but the most common are as follows:
Snaring - a wire is passed around the polyp and tightened which cuts the polyp off. Sometimes an electric current is passed through the snare which will cauterize any blood vessels to prevent bleeding. Snaring is like cutting the polyp off with cheese wire and is painless.
Endoscopic mucosal resection (EMR) is an alternative way of removing larger polyps and can take longer than removing smaller polyps. The endoscopist injects a saline solution into the lining of the bowel wall to lift the polyp up. This makes it easier to snare and remove the polyp. Sometimes a dye is added to the solution to make the area easier to nd should you need a further colonoscopy. The polyp is snared and removed with the help of cautery as above.
If a polyp is bigger than 2cms it may not be completely removed but some samples taken from it which will be sent to the laboratory. This is because larger polyps have a greater chance of cancerous changes within them. The site of the polyp will be tattooed. The laboratory results will be discussed with your consultant and then a decision made to recommend a further colonoscopy or an operation to remove the polyp. Removing polyps causes a risk of bleeding, which can occur immediately or up to 14 days after the procedure. This generally stops on its own but very occasionally requires a further colonoscopy or a blood transfusion. There is also a small risk of causing a hole in the bowel wall (perforation). This happens in approximately 1 in every 500 patients who have a polyp snared or 1 in every 100 patients having EMR. This may require treatment through the endoscope, by antibiotics or rarely, by an operation.
Surgery - an operation is occasionally needed to remove part of the bowel if the polyp is too large to be removed at colonoscopy by snaring or EMR, or there is concern that the polyp may be cancerous.
What happens after the polyp has been removed?
Once they have been removed all polyps are sent to the laboratory for microscopic analysis. This will show whether or not the polyp has been completely removed, whether it has the potential to become cancerous and, of course, to be sure that cancer has not already developed.
Once a polyp has been removed will I need any further checks?
Follow-up after polyp removal varies but some people will require further colonoscopies because polyps can recur. Some bowel polyps run in families. This is uncommon but if this condition is diagnosed colonoscopy checks will be at regular intervals as advised.
How Often to Check?
Depends on the risk status, current lesion, its rate of growth and degree of dysplasia
If normal LGIE in population risk, next in 10y <85y of age
Low risk:
- Hyper plastic polyp (Small / Distal ): Every 10y
- Adenomata: 1-2 small (<1 cm) adenomas: 5-yearly
High risk:
- Family history of FAP, HNPCC (Multiple cancers): Yearly
- Hyper plastic polyp (Large / Proximal / Multiple): Every 5y
- Peutz-Jeghers Syndrome: Every 2-3y
- Juvenile Polyposis Syndrome: Every 1-3y
- PTEN: Every 3-5y
- IBD / ALM / DALM - Risk of cancer increases exponentially with time. Start screening 8-10y
- IBD / ALM / DALM - After diagnosis: Second decade: 3y, Third decade: 2y, Fourth decade: Yearly
- Adenomata 3-4 small / 1 adenoma =>1cm : 3-yearly
- Adenomata High Risk 5 + / 3 + with one => 1cm: Yearly
When to Start Screening?
- Screening / Surveillance Summary
- In Average Risk Individuals 50Y +
- In increased (FHx) / high risk (Synd) - Earlier