Diverticulosis found by chance and colon screening
A colonoscopy or CT scan done for another reason often reports diverticulosis: small pouches that bulge out through weak spots in the colon wall. (MedlinePlus) It is common with age, usually causes no symptoms and needs no specific treatment. (MedlinePlus)(NICE NG147) This page covers what the finding means for colon screening, not diet, medicines or surgery.
What the finding is
- Pouches, not inflammation: diverticulosis means the pouches are there. Diverticulitis is the name when one or more of them become inflamed. (MedlinePlus)
- Common with age: more than one-third of US adults aged 50 to 59 have it, and more than two-thirds of those over 80. Most never have symptoms or problems. (MedlinePlus) The NHS says most people get some pouches as they get older. (NHS)
- No treatment needed for the pouches alone: NICE says to tell people with diverticulosis that the condition causes no symptoms and no specific treatments are needed. (NICE NG147)
Does it change colon cancer screening?
- Not a listed risk factor: for screening, the American Cancer Society counts people as average risk unless they have a personal history of colorectal cancer or certain polyps, a family history of colorectal cancer, inflammatory bowel disease, a hereditary syndrome, or past radiation to the belly or pelvis. Diverticulosis is not on that list. (ACS)
- No long-term cancer link: a 2018 review says recent studies do not identify diverticular disease as a long-term risk factor for colorectal cancer, while the risk is higher in the short period after a hospital stay for it. (Meyer 2018)
- The usual schedule applies: the ACS advises regular screening from 45 through 75 for people at average risk, and the USPSTF recommends screening from 45 to 75. (ACS)(USPSTF) See colorectal cancer screening and colorectal cancer screening tests compared.
If the same colonoscopy found polyps, the timing of the next one depends on the polyps, not the pouches; see colonoscopy after polyps. If a CT colonography showed the pouches, see CT colonography: what to expect.
After a bout of diverticulitis
This is different from pouches found by chance. Rarely, a colon cancer is mistaken for diverticulitis on a scan, so guidance looks at whether a colonoscopy should follow. (AGA 2021)
| Body | Complicated bout | First uncomplicated bout |
|---|---|---|
| AGA (2021) | Colonoscopy advised | Colonoscopy advised; may be deferred after a high-quality colonoscopy within 1 year |
| ACP (2022) | Suggests colonoscopy after a first complicated bout if none recently (conditional, low-certainty evidence) | No recommendation for colonoscopy |
| NICE NG147 (2019) | No recommendation on a colonoscopy after diverticulitis | |
- AGA timing: wait 6 to 8 weeks or until symptoms have fully settled, whichever is longer, and sooner if there are warning signs. People with repeat uncomplicated bouts follow routine screening and surveillance intervals unless warning signs appear, such as a change in stool size, low iron, blood in the stool, weight loss or belly pain. (AGA 2021)
- How often cancer is found: the AGA cites a meta-analysis of 31 studies in which colon cancer was found in 1.9% of people with diverticulitis: 7.9% after a complicated bout and 1.3% after an uncomplicated one. (AGA 2021) A 2019 meta-analysis of 17 studies found 2.1% overall and 0.5% after an uncomplicated bout. (Rottier 2019)
For how a colonoscopy is done, see screening colonoscopy: what to expect.
NHS, when to get urgent advice: (NHS)
Ask for an urgent GP appointment or get help from NHS 111 if there is blood or slime (mucus) in your poo, you have tummy pain that is getting worse or does not go away, you have a high temperature or feel hot, cold or shivery, you keep being sick and cannot keep fluid down, or you have diarrhoea for more than 7 days or are being sick for more than 2 days.
Where they differ:
- Colonoscopy after a first uncomplicated bout. The AGA advises one unless a high-quality colonoscopy was done within a year. (AGA 2021) The ACP recommends it only after a complicated bout. (ACP 2022) A 2019 meta-analysis concluded routine colonoscopy may be left out after an uncomplicated bout if the CT is otherwise clear. (Rottier 2019)
- How strong the advice is. The ACP rates its recommendation conditional, based on low-certainty evidence. (ACP 2022) NICE NG147 makes no recommendation on colonoscopy after diverticulitis. (NICE NG147)
- Cancer rates after diverticulitis. Estimates after an uncomplicated bout range from 0.5% to 1.3%, depending on which studies are pooled. (Rottier 2019)(AGA 2021)
Your doctor decides what your result means for you.
Questions people ask
Is diverticulosis a sign of colon cancer?
No. Diverticulosis means small pouches in the colon wall, and a 2018 review says recent studies do not show diverticular disease as a long-term risk factor for colorectal cancer. (MedlinePlus) (Meyer 2018)
Do I need a follow-up colonoscopy because of diverticulosis?
Not for the pouches alone. NICE says to tell people with diverticulosis that it causes no symptoms and needs no specific treatment. Your next colonoscopy depends on your screening plan and anything else the test found. (NICE NG147)
Does diverticulosis change my screening schedule?
The American Cancer Society list of things that raise colorectal cancer risk for screening does not include diverticulosis, so the usual schedule for your age applies unless something else puts you at higher risk. (ACS)
I had diverticulitis on a CT. Do I need a colonoscopy?
Guidance says it depends on whether the bout was complicated and when your last good colonoscopy was. The AGA advises one after a complicated bout or a first uncomplicated bout unless you had a high-quality colonoscopy within a year; the ACP suggests one after a first complicated bout if you have not had one recently. (AGA 2021) (ACP 2022)
How soon after diverticulitis is a colonoscopy done?
The AGA advises waiting 6 to 8 weeks or until the symptoms have fully settled, whichever is longer, and sooner if there are warning signs. (AGA 2021)