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Colonoscopy every one to two years: why so often? | CION Cancer Clinics
In Lynch syndrome a small bowel polyp can turn into cancer much faster than in other people. That is why colonoscopy starts early and is repeated every one to two years, even when the last test was clear. This page explains why the schedule is so tight, what makes a Lynch colonoscopy different, and what happens each time you go. At CION Cancer Clinics, our oncologists plan screening and care for families with an inherited cancer syndrome, explained in plain words.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- Why is colonoscopy repeated so often in Lynch syndrome?
- What makes a Lynch colonoscopy different?
- What actually happens at each colonoscopy?
- The words on a colonoscopy report, in plain language
- How does Lynch surveillance compare with ordinary screening?
- Four reasons people give for skipping a colonoscopy
- What this page cannot tell you
- Common questions about colonoscopy in Lynch syndrome
The short answer
Why is colonoscopy repeated so often in Lynch syndrome?
Because in Lynch syndrome a small bowel polyp can turn into a cancer much faster than usual, sometimes within a few years rather than the decade or more it normally takes. A longer gap between checks could let a cancer start and grow unseen. Short, regular intervals catch polyps while they can still simply be removed.
Why the polyps are harder to catch
Polyps in Lynch syndrome are often flat rather than raised, and they tend to grow on the right side of the large bowel, where the lining folds and the view is harder. A careful examiner and a well-cleaned bowel make a real difference to what is found.
Why doctors are confident it helps
A long-running study of Lynch families in Finland found that regular colonoscopy cut bowel cancer by more than half and reduced deaths. When cancers were found in people having regular checks, they were more often at an early stage. That is the evidence behind the tight schedule.
Colonoscopy in Lynch syndrome is prevention, not only detection. Removing a polyp removes a future cancer.Not an ordinary check
What makes a Lynch colonoscopy different?
The procedure is the same one anyone else has. What changes is when it starts, how often it comes round and how carefully the bowel is looked at.
It starts earlier
For most people bowel screening begins in middle age. In Lynch syndrome it starts in early adulthood, and earliest for the MLH1 and MSH2 genes.
It comes round sooner
Most guidelines advise a colonoscopy every one to two years. The exact gap depends on your gene, what was found last time and the guideline your team follows.
The gap may shorten if
- Polyps were found and removed
- The bowel was not clean enough to see well
- You have had bowel cancer before
The bowel is examined more carefully
High-definition scopes, a slower look on the way out and sometimes a dye spray on the lining all help show flat polyps that could otherwise be missed.
Polyps are removed at once
Almost every polyp can be taken out during the same procedure, with no cut on the skin. It is then sent to the laboratory to confirm what it was.
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What actually happens at each colonoscopy?
The day before
You switch to clear fluids and drink a strong laxative that empties the bowel. This is the hardest part, and it matters most. A poorly cleaned bowel can hide polyps.
On the day
You are usually given sedation through a vein. A thin, flexible camera is passed through the back passage and guided round the whole large bowel.
During the look
The doctor inspects the lining slowly on the way out. Any polyp is removed and any unusual area is sampled for the laboratory.
Afterwards
You rest until the sedation wears off and need someone to take you home. Most people eat normally the same evening. The laboratory report follows, and your next date is set from it.
On your report
The words on a colonoscopy report, in plain language
- Adenoma
- A polyp that is not cancer but could become one. Removing adenomas is the main way colonoscopy prevents bowel cancer.
- Caecum reached
- The camera got to the far end of the large bowel. It confirms the whole bowel was seen.
- Bowel preparation quality
- How clean the bowel was. A poor score may mean the test is repeated sooner, because polyps could have been hidden.
- Chromoendoscopy
- A dye sprayed onto the lining during the test to make flat polyps stand out.
- Interval cancer
- A cancer found between scheduled checks. Short intervals exist to make these as rare as possible.
- Surveillance interval
- The gap until your next colonoscopy, set from your gene, your history and what this test found.
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Side by side
How does Lynch surveillance compare with ordinary screening?
In Lynch syndrome
In the general population
Starts in early adulthood
Starts in middle age
Repeated every one to two years
Long gaps after a clear test
A polyp can become cancer quickly
A polyp usually changes slowly
Stool tests are not a substitute
Stool tests are often used first
A clear result covers a short period only
A clear result reassures for many years
Commonly believed
Four reasons people give for skipping a colonoscopy
"My last colonoscopy was clear, so I can leave the next one."
A clear test tells you about that day only. In Lynch syndrome a new polyp can appear and change quickly in the gap. The schedule already assumes the last test was clear.
"A stool test would be easier and just as good."
Stool tests look for hidden blood and miss many polyps. They are useful for the general population, not for someone whose polyps can turn quickly. They are not a replacement for colonoscopy in Lynch.
"Having so many colonoscopies must be dangerous."
Serious problems such as bleeding or a tear in the bowel are uncommon, and more likely when a large polyp is removed. For a Lynch carrier, the risk of missing a cancer is far greater than the risk of the test.
"I have had bowel surgery, so I no longer need it."
Unless the whole large bowel was removed, the part that remains can still form polyps. Checks continue after surgery, sometimes with a different gap. Your surgeon will tell you what applies.
Being straight with you
What this page cannot tell you
It cannot set your own schedule. Guidelines differ on the exact gap and the age to start, and your gene, your past findings and your family history all change the answer. Your gastroenterologist and genetics team decide that together.
It cannot promise that colonoscopy prevents every cancer
Even with regular checks, a small number of cancers appear between tests. They are usually found earlier than they would otherwise have been. Report new symptoms such as bleeding, a change in bowel habit or weight loss, even if your last test was recent.
Who this does not apply to
Most people do not need colonoscopy this often. If you have not been told you carry a Lynch gene fault, and no relative has, ordinary screening advice applies to you. Relatives who test negative for the family's fault also return to ordinary screening.
It cannot remove the practical burden
Travelling from a district, taking a day off work and bringing someone to take you home all add up, especially when several relatives need the same test. Some families try to space checks further apart for these reasons. Talk to your team first. They may be able to arrange the test closer to home, or plan relatives' visits together.
Questions we are asked
Common questions about colonoscopy in Lynch syndrome
At what age should colonoscopy start?
It depends on the gene. For MLH1 and MSH2 it usually starts in the twenties, and for MSH6 and PMS2 somewhat later. A relative diagnosed very young can bring the start forward. Your genetics team will give you a date based on your report.
Is colonoscopy painful?
Most people are sedated and remember little of it. Some feel cramping or bloating as air is passed into the bowel, which settles quickly afterwards. Tell the team if you have found it uncomfortable before, so they can plan your sedation.
What if my bowel preparation was poor?
Polyps may have been hidden, so the test is often repeated sooner. Ask for a split preparation, taken partly the evening before and partly on the morning of the test. Following the diet instructions closely also helps.
Can I have the test closer to home?
Possibly, if the centre has an experienced endoscopist and good equipment. What matters is the quality of the look, not the building. Ask for the full report each time and keep them together, so the next team can compare.
Does aspirin mean I can have fewer colonoscopies?
No. Aspirin has been shown to lower bowel cancer risk in Lynch carriers, but it is added to colonoscopy, never used in its place. Discuss whether it suits you before starting, because it is not safe for everyone.
What if a cancer is found during surveillance?
Cancers found on regular checks are usually at an early stage, when treatment works best. Your surgeon may discuss removing more of the bowel than usual, because of the Lynch risk. That decision is made with you.
Do women with Lynch syndrome need other checks too?
Yes. Colonoscopy looks only at the bowel. Women also carry a raised risk of womb and ovarian cancer, and need their own plan for those, including knowing which bleeding symptoms to report straight away.
Where do I start?
Find your genetic report and your last colonoscopy report. Check when the next one is due. If you have never had one, or you are overdue, take both to a gastroenterologist. The CION helpline can point you to the right clinic.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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Sources
- GeneReviews (NCBI) — Lynch Syndrome
- National Cancer Institute — Genetics of Colorectal Cancer (PDQ) - Health Professional Version
- NHS — Colonoscopy
- MedlinePlus Genetics — Lynch syndrome
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Lynch syndrome: the complete picture across organsWhere the bowel fits among every organ affectedAspirin for Lynch syndrome: what the evidence showsThe tablet added alongside colonoscopy, and who it suitsGastric and small bowel surveillance in LynchThe checks above the large bowelLiving with Lynch syndrome in a large familyKeeping many relatives on schedule at once
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Is your next colonoscopy due, or overdue?
Tell us your Lynch gene and when your last colonoscopy was done. We will help you arrange the next one with an experienced team and make sure the report reaches your genetics plan. One helpline serves every CION centre.