A step-by-step walkthrough

In short

From the moment you walk through the door to the moment you walk out of it, a routine coloscopy day takes between two and four hours, of which the test itself is the shortest part. Most of that time is checking in, getting changed, having an intravenous line placed, recovering from the sedation if you have any, and being cleared to leave. Knowing what each step is and roughly how long it lasts makes the day quieter.

What this page covers

An ordered walkthrough of a typical coloscopy day in an outpatient endoscopy unit or hospital day-case ward. Local practice varies — your unit may do things in a slightly different order, ask different questions, or use different equipment — but the underlying sequence is the same almost everywhere.

Arrival and check-in
The pre-procedure assessment, gown, and IV
Walking or being wheeled into the procedure room
The exam itself, in plain terms
Waking up and recovery
Discharge, and what you are usually told before you leave

Step 1 — Arriving and checking in

Aim to arrive at the time on your letter, not earlier. Endoscopy units run on a tight list and arriving an hour early often means an hour sitting in the corridor; arriving fifteen minutes early is enough.

At reception you will give your name, date of birth, and address; show your ID and your insurance or coverage information; and confirm the name and phone number of the person collecting you. Some units also ask for an emergency contact and a next of kin. If you have completed paperwork online, this stage is faster; if not, you will be given consent forms to read and sign. The consent form lists the procedure, the anticipated benefit, the main risks (bleeding, perforation, sedation-related events, missed lesions), and the alternatives. You will have the chance to ask questions before signing.

From reception you are usually shown to a small changing area or cubicle.

Step 2 — Changing and the pre-procedure assessment

You will be given a hospital gown that opens at the back, a paper undergarment with a flap at the back (designed to preserve dignity during the test while leaving access to the area the scope passes through), socks, and a bag for your clothes. Take everything off — including bra, jewellery, and any piercings the team has asked about — and leave glasses on for now. Hearing aids and dentures are usually kept in until just before the test; the team will tell you when to remove them.

A nurse will then take you through a pre-procedure assessment. Expect questions about:

Your medical history, including heart, lung, kidney, and liver conditions
Any previous reactions to anaesthesia or sedation
Allergies — drugs, latex, adhesive, foods
The medications you take, with particular attention to blood thinners, diabetes drugs, and GLP-1 medications — see blood thinners and antiplatelets, diabetes and bowel prep, and GLP-1 medications
When you last ate and last drank anything
How the prep went and what your stool looked like at the end
Whether you have any loose teeth, crowns, or dental work that should be noted
Whether there is any chance you might be pregnant

Your blood pressure, pulse, oxygen level, and sometimes temperature will be checked. The nurse will then place an intravenous (IV) line, usually in the back of the hand or the inside of the forearm. The cannula stings briefly going in and is then taped down; you will feel its presence but not pain. A bag of clear fluid may be connected to keep the line open and to help with hydration after the prep.

The endoscopist (the doctor or nurse who will do the test) will come and introduce themselves, confirm what is planned, ask if you have any final questions, and review consent. If an anaesthesia clinician is giving your sedation, you will meet them at this stage too.

Step 3 — Into the procedure room

When the team is ready you will be walked the short distance to the procedure room or wheeled there on a trolley. The room itself is plainer than people expect — a trolley in the centre, a stack of monitors and the video screen on one side, the trolley with the colonoscope and accessories on the other, and three to five staff: the endoscopist, one or two endoscopy nurses, and (depending on sedation) an anaesthetist with their own assistant.

You will be helped onto the trolley and asked to lie on your left side, with your knees drawn up towards your chest. This is the standard starting position. Stickers (ECG leads) are placed on your chest, a finger clip (pulse oximeter) on a finger, and a blood pressure cuff on the opposite arm. A small tube delivering oxygen is fitted at the nose. If a mouthpiece is used (occasionally, to position the head), it goes in now.

The endoscopist or anaesthetist will then say something like "I'm giving you the medication now." With propofol-based deep sedation, sleep follows within a minute. With moderate sedation using midazolam and fentanyl, you become drowsy and detached but may remember fragments. With an unsedated approach you stay aware throughout. See sedation options for the differences.

Step 4 — The examination

The colonoscope is a flexible tube about the thickness of an index finger, with a camera and a light at the tip. Lubricating jelly is applied; the scope is passed through the anus into the rectum and then advanced gently around the bends of the large bowel — sigmoid colon, descending colon, the splenic flexure on the left, the transverse colon, the hepatic flexure on the right, and the ascending colon — until the tip reaches the caecum (the first part of the large bowel) or, in some cases, the very end of the small bowel (terminal ileum).

To allow a clear view, the bowel is gently inflated. Most modern units use carbon dioxide rather than air, because carbon dioxide is absorbed quickly and produces less bloating afterwards. Water may also be used to wash any residue from the bowel wall — see signs prep is working for what a well-prepared bowel looks like to the team.

Most of the careful inspection happens on the way back, as the scope is slowly withdrawn. The endoscopist looks at the lining centimetre by centimetre, taking still images, measuring anything notable, and removing polyps as they are found, using small instruments passed through a channel in the scope. You will not feel polyp removal; the inner lining of the colon does not have the kind of sensory nerves that produce pain. Tissue samples (biopsies) for the laboratory are taken in the same way.

The whole examination — insertion to withdrawal — usually lasts twenty to forty-five minutes. It is longer if many polyps are found or if the bowel is unusually long or fixed.

Step 5 — Waking up and recovery

If you have had sedation, you will not remember coming out of the room. You wake gradually in a recovery bay — a curtained or partitioned space with a recliner or a bed — with a blanket on you and the same monitoring still attached. A nurse will be nearby. Most people are mildly disoriented for the first few minutes, then drowsy and slightly chatty for the next half hour, then progressively more themselves over the following hour or two.

Two things are normal and almost universal in recovery:

Gas. The bowel was inflated for the test and that gas needs to come out. Passing wind, sometimes a great deal of it, is expected and encouraged. Patients sometimes feel embarrassed; the staff are pleased.
A small amount of bleeding, usually streaks of bright red on the underwear or the toilet tissue after the first stool. This is more common if polyps were removed or biopsies taken, and is not a worry on its own. See when to call your doctor after for the signs that need attention.

Once you are awake enough, you will be offered something to drink — water, tea, biscuits — and helped to dress. The IV is taken out before you leave, leaving a small piece of tape and sometimes a bruise the size of a thumbprint that fades over a few days.

Step 6 — Discharge

Before you leave, the endoscopist or a nurse will tell you what was found. With sedation on board you may not remember this conversation in detail, which is why most units also give you written discharge information. Expect some of the following:

Whether the test was complete (the scope reached the caecum) and the quality of the prep
Whether anything was removed (polyps, biopsies) and roughly when the laboratory results will be available
An initial recommendation about the next test, which may be modified once the pathology comes back — see surveillance intervals and pathology report glossary
What to do for the rest of the day and the next twenty-four hours — see the first twenty-four hours
Symptoms that should make you call back urgently — fever, severe abdominal pain, heavy bleeding
Who to contact and how

You will need to be collected by a responsible adult who can take you home and stay with you for several hours. You should not drive, sign legal documents, return to work, or be solely responsible for children for the rest of the day.

What to ask your clinician

What time should I really arrive? Is there a separate check-in for endoscopy?
Will I meet the endoscopist before I am sedated, and the anaesthetist if there is one?
Where will my partner or escort wait during the procedure, and how will they be told when I am ready?
Will the team use carbon dioxide insufflation? Water immersion or water exchange?
Will I be told the results before I go home, and in writing?
Who do I call if something is wrong tonight or tomorrow?

Common worries, briefly addressed

I am worried about being naked under the gown.

The paper undergarment is designed for exactly this concern: a back flap opens only when the test starts and only the area that has to be exposed is exposed. A drape covers the rest. Endoscopy teams are practised at this and the room is not the casual environment people imagine.

What if I need the toilet between checking in and going into the room?

Tell the nurse — there is always a toilet in the changing area, and it is normal to need it more than once before the test starts. Better to go now than to feel uncomfortable on the trolley.

Will the team see if my prep was poor?

Yes, and they will tell you. A poor prep does not mean you have done anything wrong; preps are difficult, and the unit's job is to grade what they see and decide whether the test is reliable. Sometimes a repeat is recommended sooner than otherwise; sometimes the test is good enough.

Can I keep my hearing aids in?

Usually yes, until just before the medication is given, so you can talk with the team. They are removed for safety once you are sedated and given back in recovery. Tell the nurse when you check in so they keep them in a labelled bag.

Will I feel anything?

With sedation, almost always nothing. With unsedated coloscopy, predictable cramping at the bends of the bowel and when air or water is used. See pain and discomfort, during and after for a fuller answer.

Sources

American Society for Gastrointestinal Endoscopy — quality indicators for colonoscopy
American College of Gastroenterology — patient information on what to expect
European Society of Gastrointestinal Endoscopy — performance measures for lower gastrointestinal endoscopy
British Society of Gastroenterology — quality standards for endoscopy
National Institute for Health and Care Excellence — guidance on bowel cancer diagnosis and pathways