An inflammatory polyp is a non-cancerous growth that forms on the inner lining of the colon or rectum as a reaction to injury or inflammation. It is not cancer, it is not precancerous, and finding one does not mean cancer is present or likely. These polyps develop when the colon lining is repeatedly damaged — by inflammation, infection, or other causes — and the healing process produces a raised, polyp-like projection of tissue.
Inflammatory polyps are sometimes called pseudopolyps because they are not true tumours. They form from scar-like healing tissue rather than from abnormally dividing cells. This distinguishes them from other types of colon polyps, such as adenomas or sessile serrated lesions, which carry a genuine risk of becoming cancer over time. Inflammatory polyps carry no such inherent risk. Inflammatory polyps can develop anywhere in the colon, but they are most commonly found in the sigmoid colon and rectum.
What causes an inflammatory polyp?
Inflammatory polyps form when the colon lining is repeatedly injured, and the tissue responds by growing outward as it heals. Several conditions can trigger this process:
- Inflammatory bowel disease (IBD). This is the most common setting in which inflammatory polyps are found. People with ulcerative colitis or Crohn’s disease frequently develop inflammatory polyps in areas of the colon that have been chronically inflamed. These polyps are a marker of past and ongoing injury, not a separate disease in themselves.
- Infections. Certain bacterial, viral, or parasitic infections of the colon can irritate the lining enough to cause temporary inflammatory polyps. These typically resolve when the infection is treated.
- Diverticular disease. Inflammation around diverticula — small pouches in the colon wall — can produce inflammatory polyps in the surrounding tissue.
- Ischemia. Reduced blood flow to part of the colon can damage the lining and trigger a healing response that results in an inflammatory polyp.
- Radiation therapy. Radiation directed at the abdomen or pelvis can injure the colon lining and cause inflammatory changes, including polyp formation.
- Chronic constipation and straining. Prolonged mechanical irritation of the colon wall may contribute to localised inflammation and polyp development, though this is a less common cause than those listed above.
What are the symptoms?
Many inflammatory polyps cause no symptoms at all and are found incidentally during a colonoscopy performed for another reason. When symptoms are present, they are usually caused by the underlying condition that produces the inflammation rather than by the polyp itself. They may include:
- Diarrhea or loose stools — particularly in people with inflammatory bowel disease.
- Mucus in the stool.
- Rectal bleeding — especially if the polyp surface is eroded or ulcerated.
- Abdominal cramping or discomfort.
- A sensation of incomplete bowel emptying.
A large inflammatory polyp may occasionally cause partial bowel obstruction, but this is uncommon.
How is the diagnosis made?
Inflammatory polyps are usually visible during a colonoscopy — they tend to project outward from the colon lining and can be seen directly through the camera. They are typically removed during the same procedure, either by polypectomy (using a wire loop) or with biopsy forceps for smaller polyps. Removing the polyp at the time of colonoscopy both confirms the diagnosis and treats it.
The removed tissue is sent to a pathologist, who examines it under a microscope. The pathologist looks for the characteristic features of an inflammatory polyp and confirms that no precancerous or cancerous changes are present.
What does the pathology report describe?
Microscopic appearance
Under the microscope, an inflammatory polyp shows a combination of features related to inflammation and healing rather than abnormal cell growth. The pathologist may describe some or all of the following:
- Normal glands with surrounding inflammation. The glands that line the inside of the colon are typically still present and structurally intact. Still, they are surrounded by large numbers of immune cells — including neutrophils and plasma cells. This pattern reflects an active immune response to injury.
- Reactive changes. The glands may appear slightly distorted or irregular — not because they are abnormal in a precancerous sense, but because they have adapted in response to the surrounding inflammation. Pathologists describe this appearance as “reactive.”
- Granulation tissue. In larger polyps, some of the normal glandular tissue may be replaced by granulation tissue — a healing tissue made up of new small blood vessels and inflammatory cells. This is a normal part of the body’s repair process after injury.
- Erosion. The surface of the polyp may show areas where the protective lining of cells has been damaged or lost. This is called erosion and is a sign of recent or ongoing injury at the surface of the polyp.
Dysplasia
Dysplasia — abnormal precancerous cell changes — is very rarely found in inflammatory polyps. When it does occur, it is almost exclusively in people with long-standing inflammatory bowel disease, where chronic repeated inflammation over many years can eventually cause cells to develop abnormal features. If dysplasia is present, the pathology report will state this clearly, because it affects follow-up and management. Your doctor will discuss what it means for your specific situation.
Margin
The margin is the edge of the tissue that was removed. The pathologist examines it to determine whether the entire polyp was taken out.
- Negative margin (clear margin). No polyp tissue is found at the cut edge, meaning the polyp appears to have been completely removed.
- Positive margin. Polyp tissue is present at the edge, suggesting some may remain. Because inflammatory polyps are benign, this is less concerning than in a precancerous polyp — but your doctor may recommend a follow-up inspection of the removal site.
- Cannot be assessed. If the polyp was fragmented during removal or the edges were cauterised, the margin may not be reliably evaluable. This is common and generally not a cause for concern.
What happens next?
In most cases, no further treatment is needed once an inflammatory polyp has been removed. The polyp itself is benign, and removing it is both diagnostic and curative for that particular growth.
What comes next depends primarily on the underlying condition that caused the inflammation:
- If no underlying condition is identified. For patients without a known history of IBD or another ongoing inflammatory condition, no additional follow-up specific to the polyp is usually required. Routine colonoscopy screening continues as normal.
- If IBD is the underlying cause. People with ulcerative colitis or Crohn’s disease require ongoing colonoscopy surveillance regardless of whether inflammatory polyps are found. Chronic inflammation from IBD — not the inflammatory polyp itself — increases the long-term risk of colorectal cancer over many years. The presence of inflammatory polyps indicates repeated inflammation in the colon, underscoring the importance of regular surveillance. Your gastroenterologist will determine the appropriate surveillance interval based on your disease history, extent of colon involvement, and whether any dysplasia was found.
- If the polyp was large or difficult to remove. Your doctor may recommend a follow-up colonoscopy to confirm that the site has healed and that the polyp has not regrown.
- If dysplasia was found, this is a more significant finding that will require a discussion with your gastroenterologist about surveillance frequency and possibly referral for specialist review. The management of dysplasia in the setting of IBD requires individual assessment and is different from how dysplasia in a sporadic polyp is handled.
Questions to ask your doctor
- What caused the inflammation that led to this polyp?
- Was the polyp completely removed?
- Was dysplasia found in the polyp?
- Do I need a follow-up colonoscopy, and if so, when?
- If I have IBD, how does this finding affect my surveillance schedule?
- Are there changes to my treatment or medications based on this finding?
- Should I be referred to a gastroenterologist if I am not already seeing one?
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