Can Diverticulitis Turn Cancerous?

This article is based on anonymised discussions from our Diverticulitis Club Facebook group. We changed all names and locations.

Diverticulitis and colon cancer are separate diseases, and research has not proven that diverticulitis turns into cancer. Doctors do record more colon cancer diagnoses soon after a diverticulitis episode than in people who have never had one. A Danish register study of 29,173 adults with diverticulitis found colon cancer in 2.1% of them over the follow-up period, compared with 1.5% of 145,865 matched adults without diverticulitis, and the excess sat in the first six months after diagnosis. Researchers explain that early rise in several ways, including cancers that were already present and caused pain that looked like diverticulitis, which is why many doctors arrange a colonoscopy once the inflammation settles.

This article sets out what the Danish study, a Swedish study of cancer risk in diverticular disease and a Korean case report show, then compares them with what members of our group describe after their own scans, colonoscopies and waits for results. The studies measure association and timing. They do not show that one disease changes into the other, and they cannot tell any individual reader what their own result will be.

Why Do Members Worry About Cancer After A Diverticulitis Diagnosis?

Members worry because the two conditions share symptoms and because doctors often mention cancer while they order tests. Lower tummy pain, bloating and a change in bowel habit appear in diverticular disease and in bowel cancer. The Association of Coloproctology of Great Britain and Ireland states that diverticular disease symptoms can mimic bowel cancer and that tests are often done mainly to rule cancer out. A leaflet from an NHS hospital trust lists low abdominal pain, bloating, changes in bowel habit and mucus or blood in the stool as common symptoms of diverticular disease, and adds that many of them resemble more serious conditions such as bowel cancer.

Members describe that overlap as the moment the worry begins. One member listed her symptoms and the tests her doctor ordered.

“I have continuing cramps, bloating, low back pain, sore bowels at times and frequent wees. The doctor gave me anti-spasm tablets and a FIT test, then in a month’s time blood tests for gluten intolerance and to rule out anything ominous like ovarian cancer. So I am a bit worried about this.”

Hilary, Exeter

Symptoms between flares keep the question alive for other members.

“I have cramps every day and my lower back keeps hurting. I am not in a flare at the moment. My lower left side is constantly in pain.”

Donna, Columbus

A third member described what happened when she searched online from a hospital bed after a scan showed a perforated pouch.

“I started googling in the hospital while my husband ran home, and I had a full blown panic attack. I was convinced I had colon cancer. The surgeon who will do my colonoscopy told me he absolutely does not feel it is cancer and went through all of his reasons. I have allowed my brain to worry again and it is debilitating.”

Zoe, Brisbane

These accounts share three features: symptoms that persist, tests that take weeks to arrange and a doctor’s reassurance that does not remove the worry. The sections below separate what the research shows from what remains uncertain.

How Do Diverticulosis, Diverticulitis And Colon Cancer Differ?

The three conditions affect the same organ but have different definitions and different ways of being confirmed. The NHS describes the symptoms of diverticular disease and diverticulitis as similar to those of other conditions such as irritable bowel syndrome (IBS), which adds to the confusion.

Our guide to what can be mistaken for diverticulitis covers the other look-alike conditions in more detail.

What Does The Danish Research Show About Colon Cancer After Diverticulitis?

A team led by Laura Quitzau Mortensen linked Danish national health registers covering the whole population from 1995 to 2013 and published the results in the Journal of Clinical Medicine in 2024. The team compared adults admitted to hospital with a first episode of diverticulitis against five matched adults for each patient who had no diverticulitis. The average age at inclusion was 67 and 61% of participants were women.

A hazard ratio compares how fast diagnoses occur in two groups. A ratio of 1.6 means the diverticulitis group received diagnoses at about 1.6 times the rate of the control group, and a ratio of 0.8 means a lower rate. In absolute terms, 2.1% against 1.5% is a difference of 0.6 percentage points, or about six extra diagnoses per 1,000 people over the study period.

The authors believe the lower rate after six months reflects a screening effect from the follow-up colonoscopy. Earlier studies they cite found adenomas (growths in the bowel lining that doctors remove because some can become cancerous) in 14% to 31% of people who had a colonoscopy after diverticulitis. By eight years the rates in the two groups matched. The authors recommend a follow-up colonoscopy after a first diagnosis of diverticulitis and state that their results cannot settle the best timing or frequency.

The study has limits. Register data depend on doctors coding diagnoses correctly. The registers hold no information on smoking, weight or diet, which raise the risk of both diseases. The study included only people admitted to hospital, and the authors state that the results probably do not apply to countries with very different diverticulitis patterns, such as African and Asian countries. A smaller earlier study of 124 patients with a colonoscopy up to five years before diverticulitis found no raised cancer risk.

What Does The Swedish Research Show About Cancer Risk More Widely?

A team led by Wenjie Ma studied 75,704 Swedish adults with diverticular disease and a bowel biopsy, 313,480 matched adults from the general population and 60,956 siblings, and published the results in the Journal of the National Cancer Institute. The median follow-up was about six years. People with diverticular disease developed cancer at a rate of 24.5 per 1,000 person-years against 18.1 in the general population.

The researchers calculated that the difference equals one extra cancer for every 16 people with diverticular disease followed for 10 years. The rise in colorectal cancer concentrated in the first year and in early-stage disease. The team found a lower rate of rectal cancer and suggest doctors detect it earlier, at the first examination.

This study counts people with any form of diverticular disease who had a bowel biopsy, so it cannot separate diverticulosis from diverticulitis. It held no data on smoking, weight or diet, although the team adjusted for lung disease, obesity and alcohol-related disease as stand-ins. The Swedish population was mainly White. The authors call for awareness and prevention strategies for cancer in general, not only bowel cancer, and state that more research must explore the biological mechanisms.

Why Do Cancer Diagnoses Cluster Soon After Diverticulitis?

Both research teams offer several explanations, and neither claims to have settled the question. The table sets the explanations beside what the studies say and what remains unknown.

Members describe diagnostic uncertainty from the opposite direction too. One member’s first episode received a diverticulitis label that her specialist later questioned.

“My first episode of intense lower abdominal cramping was diagnosed as diverticulitis in the ER, but my gastroenterologist thinks it was a misdiagnosis. I have had about eight episodes now, lasting from a few minutes to several hours. A pelvic ultrasound looked fine, so I still have no answers. It all started about six months ago.”

Marilyn, Denver

What Did Three Korean Case Reports Show?

Doctors at Gangneung Asan Hospital in Korea described three patients whose CT scans and clinical picture first suggested acute diverticulitis and who later received a colon cancer diagnosis. The report in the Annals of Coloproctology appeared in 2013.

The CT scans of all three patients showed focal thickening of the bowel wall at the time of the diverticulitis diagnosis. On follow-up scans the wall stayed thickened or grew thicker even as the inflammation around the pouch improved. None of the three had weight loss, persistent pain, black stools or sudden constipation before admission, and none had a previous colonoscopy. The authors advise colonoscopy after diverticulitis, particularly when wall thickening persists, and recommend that doctors stress the importance of follow-up at the time of diagnosis.

The report covers only three patients, and the authors state that readers should interpret it with caution. All three cancers sat in the ascending colon on the right side. NHS 111 Wales describes pain in the lower left side as typical, with a small number of people feeling it on the right, and the members quoted in this article who locate their pain place it on the left.

Does Complicated Diverticulitis Carry A Higher Cancer Risk?

The Danish study found a higher rate of colon cancer after complicated diverticulitis (with an abscess or perforation) than after uncomplicated diverticulitis. Cancer appeared in 2% of both groups on a crude count (80 of 3,662 people with complicated diverticulitis and 531 of 25,511 with uncomplicated). After adjusting for age, bowel conditions, diabetes and recent colonoscopy, the hazard ratio for complicated diverticulitis was 1.6 (95% CI 1.2 to 2.0). The ratio fell to 1.4 (95% CI 1.01 to 1.7) once the team also adjusted for surgery. The authors conclude that the severity of the illness plays an important role in assessing risk.

One parent described this situation after her son’s abscess healed.

“My son, who is in his twenties, was diagnosed with diverticulitis in March and had an abscess drained. His CT scan after six months showed the abscess had healed completely, but a little inflammation remained. The doctors have now advised a colonoscopy and said cancer is unlikely. Do they usually do a colonoscopy after complicated diverticulitis? He feels fine and has no bowel problems. I am worried.”

Helen, Reading

Members in the thread replied that a colonoscopy follows most first flares. The Danish authors state that their data cannot set a timetable for any individual, so questions like Helen’s belong with the treating team.

Why Do Doctors Recommend A Colonoscopy After Diverticulitis?

Doctors recommend a colonoscopy to look inside the bowel and to take a biopsy if anything looks abnormal. The Danish authors report that the vast majority of international guidelines recommend a follow-up colonoscopy after diverticulitis, but the guidelines differ on who should have one.

The Danish national guideline recommends a colonoscopy once the acute phase has passed, usually six to eight weeks after the first admission. Members repeat the standard-practice message in the group.

“I think it’s standard to have a colonoscopy after a first flare, if you haven’t recently had one. The only way to truly see what’s going on.”

Ruth, Glasgow

“Don’t worry, colonoscopy is standard procedure. I also have diverticulitis and I am awaiting my fifth colonoscopy.”

Gail, Dundee

Members also pass on what the test can do beyond looking.

“If there are precancerous polyps, they will remove them during the colonoscopy.”

Rob, Tampa

Members disagree about which test is the best one. One asked whether an MRI scan counts as the gold standard, and others named colonoscopy and CT scan instead. The Korean case report explains why both views carry weight: CT is the most accurate method for diagnosing acute diverticulitis, but when an abscess, a perforation, thickened bowel wall and enlarged lymph nodes appear together, CT cannot always separate diverticulitis from cancer, and a biopsy at colonoscopy becomes necessary. One member put the point briefly.

“You need a colonoscopy to rule out cancer. A CT scan does not do that.”

Dennis, Adelaide

When Do Doctors Schedule The Colonoscopy, And Why Does It Sometimes Not Finish?

Doctors schedule the colonoscopy after the inflammation settles. The Korean authors state that colonoscopy during the acute illness carries a higher chance of perforation, pain and inflammatory narrowing, with the scope reaching the caecum (the start of the large bowel) in only 75% to 82% of cases, so they usually perform it about six weeks after treatment. Members describe a range of timings and outcomes.

“My doctor said no colonoscopy for eight weeks after a flare. I had a CT scan and an MRI.”

Alan, Cork

“I had a colonoscopy just under a month after a big flare. Personally, I was still healing and had more inflammation.”

Neil, Ipswich

“My gastroenterologist could not do my colonoscopy because I was so inflamed. He ordered a CT scan, which showed bad inflammation plus an abscess, so he sent me to the ER. We are waiting for the inflammation to subside to try again.”

Lynn, Phoenix

A colonoscopy can also stop partway for another reason. One member with long-standing ulcerative colitis had her routine five-yearly colonoscopy end early and learned about her diverticulitis that way.

“No one, including my consultant, knew I had diverticulitis until my routine colonoscopy. I have had ulcerative colitis for around 40 years, so I have a colonoscopy every five years to check all is as it should be. It was the first time I had ever experienced such severe pain during the procedure. The colonoscopy was stopped and a CT scan ordered. A lot of symptoms overlap with inflammatory bowel diseases, so there was no way of knowing beforehand.”

Janet, Belfast

Our article on whether a colonoscopy is as bad as people fear covers what members say about the procedure itself.

Do Members Still Hear That Diverticulitis And Cancer Are Not Connected?

Members hear both messages, and they do not always know which one to trust. One member stated the view confidently.

“Diverticulitis is not a cause of cancer, nor are they connected. They have plenty of studies that show this.”

Rob, Tampa

Patient leaflets from Whittington Health NHS Trust say the same: they state that diverticular disease and cancer have no connection and that the two simply occur at similar ages with overlapping symptoms (second leaflet). The registry studies above ask a different question. They compare how often doctors diagnose cancer in people with and without diverticulitis or diverticular disease, and they report an association that concentrates in the first months after diagnosis. They do not show that the inflammation turns into cancer, and the Korean report states that the relationship between the diseases remains controversial. The two messages therefore address different questions, which explains part of the confusion members describe.

How Do Members Cope While They Wait For Results?

Members describe fear that reassurance does not fully remove. One long-standing member explained that repeated normal results do not end the worry.

“Every time I have a bowel movement, seeing blood is so disheartening and scary. No matter how many tests and procedures come back normal, no matter how many times the doctors say it is not cancer, I still get freaked out.”

Shirley, Hamilton

Blood in the stool also features among the overlapping symptoms listed in the NHS trust leaflet, which asks readers to consult a doctor when symptoms change or increase, especially when blood appears.

Other members value the group for comparison, not for answers.

“It’s good to be part of some of these groups because everyone is different. You can compare yours with others and see what works and doesn’t work for everyone.”

Tony, Leicester

What Questions Do Members Ask In The Group?

Members posted a handful of questions in the threads this article draws on. They are the questions members wanted answered, not advice.

• • Do doctors usually arrange a colonoscopy after complicated diverticulitis? (Helen asked this about her son.)
  • What does the air pocket on my CT scan mean, and why does it still hurt? (Zoe asked both.)
  • Can imaging explain why a little inflammation remains after treatment? (Helen asked whether an MRI could show this.)

Where Can You Read More On Diagnosis And Follow-Up?

Frequently Asked Questions

Can Diverticulitis Turn Into Colon Cancer?

Research has not proven that it does. The Danish and Swedish studies show more colon cancer diagnoses soon after diverticulitis, and the authors offer explanations that include cancers already present, closer medical scrutiny and shared risk factors. Some earlier researchers proposed that chronic inflammation in pouches could lead to cancerous change, and others found no link (Oh et al.). Your own doctor can explain what applies to your scans.

Does Having Diverticulosis Alone Raise My Cancer Risk?

Patient leaflets from Whittington Health NHS Trust state that diverticulosis and cancer are not connected. The Swedish study found higher cancer rates in people with diverticular disease and a bowel biopsy, but it could not separate diverticulosis from diverticulitis, so it cannot answer the question for pouches alone.

Do I Need A Colonoscopy After A Diverticulitis Flare?

Most international guidelines recommend one, but they differ on who should have it: all patients, only those with complicated diverticulitis, only those with persisting symptoms or only those without a recent colonoscopy. The Danish national guideline recommends a colonoscopy once the acute phase has passed. Your doctor decides based on your scan, your symptoms and your history.

Can A CT Scan Rule Out Cancer?

A CT scan diagnoses diverticulitis accurately, but it cannot always separate diverticulitis from colon cancer when an abscess or perforation is present. The Korean authors state that when thickened bowel wall and enlarged lymph nodes appear together, a biopsy during colonoscopy becomes necessary.

How Long After A Flare Does A Colonoscopy Take Place?

The studies cited here describe a gap of about six to eight weeks after the acute episode. Members report waits from just under a month to eight weeks, and one member’s colonoscopy waited until her inflammation settled.

Why Did The Danish Study Find Lower Cancer Rates After Six Months?

The authors believe the follow-up colonoscopy produced a screening effect, because doctors found and removed growths before they became cancer. The lower rate lasted until about eight years, and the groups then matched. The finding describes groups of people and cannot show protection for any one person.

Can Cancer Be Mistaken For Diverticulitis?

Yes. The Danish authors raise misdiagnosis at the first admission as one explanation for cancers found within six months, and the Korean case report describes three people whose CT scans suggested diverticulitis and whose colonoscopies later showed cancer. Our guide to what can be mistaken for diverticulitis covers other look-alike conditions.

More Reading

How Do I Know If My Pain Is Diverticulitis?

The Best 10 Food and Symptoms Diaries, Journals and Apps for Understanding Diverticulitis

What Is The Difference Between Diverticulitis And Diverticulosis (Diverticular Disease)?

What Age Do People Get Diverticulitis?

Ultimate Guide to Diverticulosis and Diverticulitis

Key Takeaways

• • Diverticulitis and colon cancer are separate diseases, and research has not proven that diverticulitis turns into cancer.
  • A Danish study of 29,173 adults found colon cancer in 2.1% of people with diverticulitis and 1.5% of matched controls, with the excess in the first six months.
  • A Swedish study found a 33% higher overall cancer rate in people with diverticular disease and a bowel biopsy, equal to one extra cancer for every 16 people followed for 10 years.
  • Researchers explain the early rise through cancers already present, closer scrutiny, shared risk factors and possible inflammation, and no single explanation is settled.
  • The Danish study found a higher colon cancer rate after complicated diverticulitis than after uncomplicated diverticulitis.
  • Most guidelines recommend a follow-up colonoscopy about six to eight weeks after the episode, but guidelines differ on who should have one.
  • Members describe delayed, incomplete and repeated colonoscopies and the worry that waiting creates, so bring your own questions to your own doctor.

Sources

• • Mortensen LQ, Andresen K, Thygesen L, Pommergaard H-C, Rosenberg J. Diverticulitis Is Associated with Increased Risk of Colon Cancer: A Nationwide Register-Based Cohort Study. Journal of Clinical Medicine, 2024 (PMC11084441).
  • Ma W, Walker MM, Thuresson M, et al. Cancer risk in patients with diverticular disease: a nationwide cohort study. Journal of the National Cancer Institute (PMC9830486).
  • Oh KH, Han KH, Kim EJ, et al. Colon Cancer After Acute Diverticulitis Treatment. Annals of Coloproctology, 2013;29(4):167 to 171 (full text).
  • Association of Coloproctology of Great Britain and Ireland. Diverticular disease patient leaflet.
  • Diverticular disease and diverticulitis.
  • NHS 111 Wales. Diverticular disease and diverticulitis.
  • Wrightington, Wigan and Leigh NHS Foundation Trust. Diverticular disease patient leaflet.
  • Whittington Health NHS Trust. Patient leaflets on diverticulosis and diverticular disease.

Members who want to track their own patterns can start the Food And Symptoms Diary or join the conversation in our support forums and our Facebook group. Reading what other members experience will not answer your own medical questions, but it shows you that you are not alone with them.

Disclaimer: This article does not constitute medical advice. Diverticulitis affects everyone differently. Always seek advice from a qualified medical practitioner about your own symptoms, diagnosis and treatment.