Explaining a Colonoscopy – OSCE Guide

If you'd like to support us, check out our awesome products:

This article provides a step-by-step guide to explaining a colonoscopy in an OSCE setting, including information you will be expected to give and how to structure the consultation.

This guide will cover what a colonoscopy is, what the procedure involves and the risks of the procedure.

Opening the consultation

Wash your hands and don PPE if appropriate.

Introduce yourself to the patient including your name and role.

Confirm the patient’s name and date of birth.

Explain the reason for the consultation: “I understand that you’re here to talk about having a colonoscopy, is this correct?”.

Due to the sensitive nature of the consultation, it’s important to establish a good rapport and open line of communication with the patient early in the consultation: “If you have any questions at any point, or if something is not clear, please feel free to interrupt and ask me.”

Make sure to check the patient’s understanding at regular intervals throughout the consultation and provide opportunities to ask questions (this is often referred to as ‘chunking and checking’).

Throughout the consultation, be receptive to the patient’s language and try only to use words and terminology they are comfortable with.

You might also be interested in our premium collection of 1,300+ ready-made OSCE Stations, including a range of communication skills and counselling stations ✨

Ideas, concerns, and expectations

A key component of history taking involves exploring a patient’s ideasconcerns, and expectations (often referred to as ICE) to gain insight into the patient’s thoughts about having a colonoscopy, what they are worried about and what they expect from the consultation. When discussing concerns, do so in a sensitive and honest manner.

It can be challenging to use the ICE structure in a way that sounds natural in your consultation, but we have provided several examples for each of the three areas below.


  • “What do you already know about having a colonoscopy?”


  • “Is there anything worrying you about having a colonoscopy?”


  • “What were you hoping we would cover today relating to having a colonoscopy?”
  • “Is there anything you particularly wanted to focus on or discuss today?”
  • “What are you hoping to get out of this consultation?

Patient history

Although the purpose of this station is to explain the procedure, it is a good idea to gather a quick, focused history early in the consultation.

This should include exploring the patient’s condition and reason for requiring a colonoscopy: “Just so we are on the same page, could you tell me a bit about why you need a colonoscopy?”

Understanding the indication for the procedure will allow you to tailor your explanation.

What is a colonoscopy?

Explain to the patient colonoscopy is a procedure to look at the lining of the colon (large bowel) performed by an endoscopist (a doctor or specialist nurse). A long, thin, flexible tube with a camera (colonoscope) is passed through the anus and into the colon (large bowel), allowing the endoscopist to visualise the bowel.

Colonoscopy also allows biopsies to be taken and the painless removal of any suspicious growths (polyps).1,2,3

“A colonoscopy is a test to look inside your colon/large bowel. A long, thin, flexible tube with a camera on the end (colonoscope) is passed into your bottom/back passage. We will be able to have a clear view of the bowel and may take some samples called biopsies.”

Why is a colonoscopy performed?

Colonoscopy is the main diagnostic investigation for colon cancer. However, it can diagnose and monitor other bowel conditions (e.g. Crohn’s disease, diverticular disease, and ulcerative colitis). 

Indications for performing a colonoscopy include:4,5

  • Rectal bleeding or blood in the stool (either occult or detected via a faecal immunochemical test)
  • Changes in bowel habit (persisting for more than six weeks)
  • Men or non-menstruating women with unexplained iron deficiency anaemia
  • Unexplained weight loss
  • Persistent abdominal symptoms with raised faecal calprotectin or CRP

Colonoscopy can also be used as a screening tool for polyps and bowel cancer.3, 6

“Colonoscopy is used to look inside your bowels when you have symptoms like blood in the poo, a change in bowel habit, or unexpected weight loss. It is also used as a screening test for bowel polyps and bowel cancer. Screening is testing for a disease when you have no symptoms, aiming to catch the disease early before symptoms appear.”

What are polyps?

Polyps are growths of cells protruding from the lining of the bowel. Polyps can be attached to the bowel by a stalk, but others are flat. Generally, polyps seen on colonoscopy are removed and sent for histology. Most polyps are benign, but there is a chance of them being pre-cancerous or cancerous.4, 5, 7

“Polyps are little growths of cells in the bowel. The majority are not serious and will never cause you any problems. When polyps are found, they are removed by the endoscopist to be looked at in more detail as there is a chance they could grow and later cause problems.”

What are the alternatives to colonoscopy?

Colonoscopy is not appropriate for some patients. The main alternative is CT colonography (CTC) or ‘virtual colonoscopy’.3

CT virtual colonoscopy is a diagnostic imaging test. It is minimally invasive and doesn’t require sedation. A small tube is inserted into the rectum, and air is pumped in to expand the colon. The CT scanner takes images of the large bowel from different angles, and a 3D model is created.

This can provide detailed images of the colon and is less invasive than a traditional colonoscopy. However, colonoscopy is preferred as it allows detailed observation of the colonic mucosa, biopsies, and removal of any lesions.5

“The main alternative to colonoscopy is a CT virtual colonoscopy. This is less invasive and doesn’t involve sedation. This uses x-rays and computers to create a detailed model of your large bowel however, it doesn’t allow a direct look at the lining of your bowel or samples (biopsies) to be taken.”

Preparing for a colonoscopy

Before the colonoscopy, patients should receive a letter inviting them to the procedure and informing them of the bowel preparation required. 

Patients should eat a low-fibre diet two to three days before the procedure and increase their fluid intake. The day before the procedure, they must take a very strong laxative (e.g. Moviprep) to clear the bowel.

It is important to warn the patient this causes diarrhoea, so the patient should stay close to a bathroom. This can be very unpleasant for the patient. Patients shouldn’t eat anything on the day of the procedure but can drink clear fluids until 2 hours before the colonoscopy.5,8

“Your bowel needs to be empty for the colonoscopy so we can have a clear view, otherwise the bowel may not be clear, and we might have to repeat the test. In the days before, you will be given a diet sheet of foods you can and can’t eat. Make sure you are drinking lots of fluids. You must take a strong laxative the day before to clear your bowel. It will cause diarrhoea, so you will need to stay close to a bathroom. On the day of the colonoscopy, you won’t be able to eat but you can have clear fluids up until two hours before.”

What happens during the procedure?

On arrival

When the patient arrives, they will have the procedure’s risks explained to them and be asked to sign a consent form. Then they will be given a hospital wristband and asked to change into a hospital gown.

Basic observations will be taken, and an intravenous cannula will be inserted (usually into the back of the hand). Patients will be offered a sedative or Entonox (‘gas and air’) to make the procedure more comfortable.2,4

“When you arrive, a nurse will explain the procedure and its possible risks. You will need to sign a consent form to say you understand and agree to the procedure. You will be asked to change into a hospital gown and then have your vital signs taken, like your blood pressure, and heart rate. A cannula will be inserted, usually into the back of your hand. A cannula is a little plastic tube to give sedation and other medicines. You will be offered sedation to make you relaxed, and this will make the procedure more comfortable.”

Colonoscopy procedure

A colonoscopy takes 20 to 40 minutes. The patient is taken to a room with the endoscopist and two nurses. They will be asked to lie on their left side in the fetal position. Before inserting the colonoscope, the endoscopist will perform a rectal exam.2,4

The endoscopist will pass the colonoscope through the anus into the rectum and colon. Carbon dioxide gas inflates the colon for a better view and manoeuvring. The colonoscope will pass through the whole length of the large intestine. 

The patient may be asked to adjust their position during the procedure. This facilitates moving the scope and improves visualisation, as well as helping the patient to be as comfortable as possible. During the procedure, polyps can be removed and biopsies taken. This is not painful.2,3,4

“For the colonoscopy, you will be taken to a room with an endoscopist and two nurses. You will be asked to lie on your left side and bring your knees up to your chest. Before the doctor can insert the scope, they will need to do a finger examination of your back passage.

The endoscopist will insert the scope through the back passage and into the bowel. Air is then passed through to inflate the bowel, this gives a better view of the bowel lining. The doctor may ask you to change your position during the procedure. This helps the movement of the scope and improves their view of your bowel. It will also help make you more comfortable, so they may need you to shift around a bit. The colonoscope will go through the whole large bowel relaying pictures to a monitor. During the procedure, the doctor will remove any growths (polyps) or take a sample of cells (biopsy); this doesn’t hurt.”

After the procedure

Patients are moved to a recovery room and monitored until ready to go home. The patient should arrange for someone to take them home as they shouldn’t drive for 24 hours after the procedure. In addition, for 24 hours after the procedure, patients should have a responsible adult with them. They shouldn’t sign any legal documentation or operate heavy machinery. 3,4

Before the patient leaves, a nurse or doctor will discuss the colonoscopy findings with the patient. Specimens taken may take a further two to three weeks. These are used to confirm the endoscopic diagnosis.9

“After the procedure, you will be taken to the recovery room and nurses will monitor you until you’re ready to go home. Ensure you have arranged for someone to pick you up as you can’t drive after the procedure. Have a responsible adult with you for 24 hours after the procedure and don’t drive. After the colonoscopy, a nurse or doctor will review the results with you before leaving. However, it may take two to three weeks to receive the results of any samples (biopsies) taken during the procedure.”

What are the side effects and risks?

Common side effects of a colonoscopy include:4,5

  • Nausea
  • Bloating
  • Crampy abdominal pain
  • Minor rectal bleeding

Possible risks of a colonoscopy include:2,3,4

  • Allergic reaction to sedation, equipment or materials used
  • Heavy bleeding
  • Bowel perforation caused by the colonoscope
  • Incomplete examination requiring a repeat test
  • Small risk of missed pathology

“During and after the procedure, you may experience some abdominal pain and cramping.”

“As we inflate your bowel with air it is normal to experience cramping, bloating, discomfort and flatulence. It is normal to have a small amount of blood in the poo or from the bottom in the days following the procedure.”

“In rare cases, colonoscopy can harm the bowel. The colonoscope can cause a hole in the bowel (perforation), and some patients may experience heavy bleeding. You must seek urgent medical advice if you experience heavy bleeding, severe abdominal pain or develop a fever after a colonoscopy.”

“While colonoscopy is a safe and effective test, it is not 100% perfect. There is a small chance that during the procedure, a cancer or polyp may be missed.”

Closing the consultation

Close the consultation by summarising what you have discussed. This allows you to emphasise the key points of the consultation.

Finally, thank the patient for their time and offer them a leaflet summarising the key information.

Dispose of PPE appropriately and wash your hands.


Dr Ian Beales 

Consultant in Gastroenterology

Clinical Reader in Gastroenterology and Therapeutics


  1. NHS. What is a colonoscopy? 2022. Available from: [LINK]
  2. NHS. Colonoscopy – what happens on the day. 2022. Available from: [LINK]
  3. GOV UK. Bowel cancer screening: having a colonoscopy. 2022. Available from: [LINK]
  4. Milton Keynes University Hospital NHS. Available from: [LINK]
  5. U.S. Department of Health and Human Services. Colonoscopy. Available from: [LINK]
  6. NHS. Bowel cancer screening. 2021. Available from: [LINK]
  7. NHS. Bowel polyps. 2020. Available from: [LINK]
  8. Guy’s and St Thomas’ NHS. Colonoscopy diet advice and bowel preparation. 2019. Available from: [LINK]
  9. NHS. Colonoscopy – Results. 2022. Available from: [LINK]
  10. BSG. Guidance on the indications for diagnostic upper GI endoscopy, flexible sigmoidoscopy and colonoscopy. 2013. Available from: [LINK]


Print Friendly, PDF & Email