What to Ask Before Your Next Colonoscopy

“Questions for Your Doctor” — third in the series

The first randomised controlled trial of colonoscopy screening was published in October 2022. After decades of observational estimates claiming 60% or greater reductions in colon cancer risk, the NordICC trial enrolled 84,000 people across Norway, Poland, and Sweden, randomised half to be invited for screening and half to receive no invitation, and followed them for ten years.

The results: an 18% reduction in colorectal cancer incidence. No significant reduction in colorectal cancer death. No reduction in death from any cause. To prevent a single case of colorectal cancer, 455 people would need to be invited for screening. The procedure generates $4 billion annually in the United States alone. The evidence supporting that expenditure had never been tested in a randomised trial until 2022.

The trial did not prove colonoscopy is useless. It proved that the only randomised evidence we have shows far more modest benefits than the public has been told — while the procedure carries real risks that are rarely mentioned at the point of scheduling. A Canadian population study of 97,204 colonoscopies documented perforation in 1 in 1,200 patients, significant bleeding in 1 in 600, and death in approximately 1 in 14,000. The bowel preparation itself causes what researchers describe as a “forest fire” through the gut microbiome, with beneficial bacteria decreasing significantly and the microbial balance potentially failing to return to its original state.

And the polyps that screening finds? International studies show polyps in 32–50% of older adults, yet only 5% of people ever develop colorectal cancer. A Gastroenterology editorial acknowledged that the proportion of polyps that would progress to cancer “is low” and most removals bring “no clinical gain” to the patient. The same journal published an editorial by the NordICC researchers themselves calling overdiagnosis in colorectal cancer screening a “striking and almost complete blind spot” — not part of patient information materials, hardly mentioned in guidelines, not addressed in public debate.

These numbers rarely reach the person sitting in the gastroenterologist’s waiting room. The screening invitation arrives as a scheduling prompt, not an informed consent discussion. The complication rates, the microbiome data, the NordICC mortality finding, the overdiagnosis editorial — none of it accompanies the letter telling you it’s time for your colonoscopy.

Colonoscopy Screening: Questions for Your Doctor is a ten-question document designed to put the evidence into the conversation before the procedure happens. Eight questions address the colonoscopy itself — the trial data, complication rates, bowel preparation risks, microbiome disruption, overdiagnosis, the surveillance cycle, and non-invasive alternatives like FIT testing. Two questions address the nature of polyps — whether they may represent the body’s repair response rather than precancerous threats, and whether their removal could cause harm through barrier damage and cell seeding. The document includes a routing table so you can focus on the questions that match where you are in the process, and a printable Quick Reference page to take to the appointment.

Each question includes a Key Fact and two paragraphs of context drawn from the source material. One example:

5. Could polyps be the body’s attempt to heal damaged tissue rather than a sign that cancer is forming?

Key Fact: Inflammatory polyps represent “re-epithelialization of the damaged colonic mucosa” — essentially scar tissue regrowing over a wounded area. Researchers have proposed that even common adenomatous polyps may form as the body’s response to damage, increasing blood flow and encapsulating toxins in areas of chronic inflammation.

The evidence is drawn from Rethinking Routine Colonoscopy: Colon Health Beyond Polyps and Procedures by Unbekoming, which compiles research from the NordICC trial team (Bretthauer et al.), Robert Yoho (Butchered by Healthcare), H. Gilbert Welch, and the Gastroenterology editorial on overdiagnosis by Kalager and Bretthauer, alongside population studies, microbiome research, and traditional medicine evidence from Ayurveda and Traditional Chinese Medicine. The report covers terrain theory, gut barrier damage, cancer cell seeding, and natural strategies for colon health that the standard screening conversation never mentions.

If you or someone you know has a colonoscopy appointment coming up, print the Quick Reference page and take it with you.

Questions for Your Doctor — the series:

1. The PSA Test — available now

2. Mammogram Screening — available now

3. Colonoscopy Screening — available now

4. The Childhood Vaccine Visit — in development

5. Statin Prescription — in development

If there is a screening test, a prescription, or a procedure where you needed the right questions before you walked into the room, put it in the comments.

The Questions for Your Doctor series is available exclusively to paid subscribers.

Colonoscopy Screening: Questions for Your Doctor is available for download below.