What follow-up colonoscopy is for
After colorectal cancer, the rest of the colon remains at higher risk of developing polyps and a second tumour than in someone who never had one. Colonoscopy serves to find and remove those polyps before they turn into cancer and to check the surgical join (anastomosis). It is not the test that detects relapse in the liver or lungs: that is what CEA and CT are for. They are complementary forms of surveillance, not interchangeable.
The usual schedule
| When | What is done |
|---|---|
| Before surgery (or within the following 3-6 months) | Complete colonoscopy of the whole colon. If the tumour was obstructing and the scope could not pass, it is done after surgery to rule out a second simultaneous tumour (found in 3-5 % of cases). |
| 1 year after surgery | First follow-up colonoscopy. |
| 3 years after (if the one-year exam was normal) | Second colonoscopy. |
| Every 5 years thereafter (if they remain normal) | Periodic colonoscopies for as long as general health justifies it. |
If any of them finds advanced polyps (large adenomas, high-grade dysplasia or several), the interval is shortened, usually to 1-3 years. These schedules are those of the European and American societies (ESMO, ESGE, US Multi-Society Task Force) and the ones most Spanish hospitals follow.
Special cases
- Rectal cancer: in addition to colonoscopy, many protocols add rectoscopy or endorectal ultrasound every 3-6 months for the first 2-3 years to monitor the anastomosis, especially if no radiotherapy was given or if "watch and wait" was chosen.
- Lynch syndrome: colonoscopy every 1-2 years for life, plus surveillance of other organs (uterus, ovaries, stomach…). Read more in MSI-H / dMMR.
- Familial adenomatous polyposis (FAP) or many polyps: individualised intervals, often yearly.
- Older people or those with other illnesses: beyond a certain age or if life expectancy is limited, the benefit of continuing colonoscopies is small and stopping them can be decided. It is a legitimate conversation to have with your doctor.
The preparation: the hardest part
Cleaning out the bowel is the most unpleasant part, but the value of the test depends on it: a poor preparation means repeating it. Tips that work:
- A low-residue diet for 2-3 days beforehand (no vegetables, fruit with skin, pulses, wholemeal bread, nuts).
- Take the solution in two doses ("split"): half the night before and the other half 4-6 hours before the test. It cleans far better than all at once.
- Drink the liquid cold and through a straw, alternating with water or strained broth; it helps with nausea.
- If you have a stoma, the preparation comes out through the bag: have spare bags and protect the skin.
- Say if you take anticoagulants, antiplatelets or diabetes medication: they may need adjusting.
With sedation
In Spain colonoscopy is usually done under sedation: you feel nothing and wake up when it is over. You need someone to accompany you and you cannot drive that day. If your centre does not offer it routinely, you can ask for it.
What it may find and what happens next
- Nothing: the most common outcome. Next colonoscopy as scheduled.
- Polyps: removed during the same procedure (polypectomy) and analysed. The report will say whether they were adenomas and of what type; that sets the next interval.
- Changes at the anastomosis: often scar tissue or benign inflammation; if in doubt, a biopsy is taken.
- A new tumour: uncommon, and when found this way it is usually early-stage and curable. That is precisely what surveillance is for.
What to ask at your appointment
- Was the whole colon seen before my surgery? If not, when is my complete colonoscopy due?
- What is my colonoscopy schedule and who arranges it: gastroenterology, oncology or surgery?
- What type of polyps were removed and when is the next one due?
- If I have rectal cancer: do I also need rectoscopies?
- Up to what age, or for how long, is it worth continuing colonoscopies?
