How to prepare for a colonoscopy: the bowel prep guide nobody gives you

Everyone worries about the camera. Almost nobody warns you properly about the preparation, which is the part patients actually find hard. So here is the honest, complete version.

Colonoscopy is usually performed without sedation at Zendale, with optional anaesthesia available on request. The preparation is a somewhat inconvenient evening at home. Get the preparation right and everything else follows.

Why the prep matters so much

For us to examine the bowel wall properly, the bowel has to be empty. Any residue left behind can hide exactly what we are looking for. A small flat polyp tucked behind debris is a missed polyp, and a missed polyp is the whole point of the test wasted.

A well-prepared bowel also means a faster, more comfortable procedure. This is the single thing in the process that is entirely in your hands.

Three days before: the low-residue diet

Start easing off fibre roughly three days ahead. The goal is food that leaves little residue behind.

Good choices: white rice, white bread, plain pasta, eggs, chicken, fish, clear soups, well-cooked vegetables without skins, and plenty of water.

Avoid: beans, seeds, nuts, sweetcorn, popcorn, tomato skins, fruit skins, brown rice, wholemeal bread, and anything with visible grains. In a Nigerian kitchen the usual culprits are beans, ogbono and efo riro with plenty of leaf, and anything with corn.

The day before: clear fluids and the prep

From the morning before your procedure, no solid food. Clear fluids only, which means anything you can see through: water, clear broth, strained fruit juice without pulp, black tea, and clear isotonic drinks.

Avoid anything red or purple, as the colour can be mistaken for blood on the camera. Skip milk and anything creamy too, since they are not clear.

In the evening you take the prep solution your unit has given you. It empties the bowel over the following few hours. Plan to be at home, near a bathroom, with nothing else scheduled.

Getting the prep down

The taste is the complaint, so a few things genuinely help:

• Chill it in the fridge beforehand, as cold is much easier than warm
• Drink it steadily rather than fighting through it in one go
• Use a straw, which bypasses much of the taste
• Follow each glass with a little clear fluid to rinse your mouth
• Keep moving gently around the house; it works better than lying down

You will know it is working when what you pass becomes clear or pale yellow liquid. That is the goal. Do not stop early because you feel empty.

Your medicines

Tell the unit about everything you take, including things bought over the counter. Particular attention goes to:

• Blood thinners, which may need pausing, but only on medical advice
• Diabetes medicines, since you are not eating, so doses often need adjusting
• Iron tablets, usually stopped about a week before, as iron darkens the bowel lining
• Blood pressure medicines, which are usually continued with a sip of water

Never stop a prescribed medicine on your own. Call and ask.

On the day

Continue clear fluids until the time you are told to stop. If anaesthesia or sedation is planned, arrange an accompanying adult and transport home. Wear something comfortable, leave valuables at home, and bring your ID, any referral letter, and a list of your medicines.

Common questions

What if I vomit the prep? Pause for half an hour, then resume more slowly. If you cannot keep any of it down, call the unit.

What if it has not worked by bedtime? Call. Sometimes an extra measure is needed, and it is far better to sort it out the night before than to arrive unprepared.

Can I take my usual painkillers? Paracetamol is generally fine. Avoid anti-inflammatories such as ibuprofen and diclofenac unless told otherwise.

The evening in perspective

One inconvenient evening buys you a complete look at your large bowel, with any polyps removed before they can become anything. Patients tell us afterwards that the prep was the worst of it and still nothing like as bad as they had built it up to be.

If anything about your preparation is unclear, call the unit on 070 7056 6272. We would far rather answer a question the night before than reschedule you on the day.