Colonoscopy Q&A

Two of our leading colorectal specialists answer common questions on the colonoscopy procedure including the risks, side effects, results and possible alternatives.

Mr Simon Radley

Colonoscopy is a diagnostic examination of the large bowel. This involves the doctor passing a flexible telescope around the bowel. This allows the doctor see a magnified image of the lining of the bowel directly. Photographs can be taken, tissue samples (known as biopsies) can be taken. Small and sometimes even large polyps can be removed. Polyps are warty type growths in the bowel, some of which can turn cancerous.

The doctor who performs your procedure should be able to complete a whole colon examination in at least 90% of people.


Mr Prateesh Trivedi

Colonoscopy is when a flexible fibre optic scope (colonoscope) is inserted via the back passage to visualise the lining of the large bowel.

Mr Simon Radley

The most common reason we do colonoscopy is as a diagnostic test. Usually this is to investigate a cause of bleeding from the bowel or a change in bowel habit. Colonoscopy is also performed as part of the national bowel cancer screening project for people who have positive tests for blood in their stools.

We also perform colonoscopy in patients with a family history of bowel cancer who may be at higher risk than the general population. We also perform colonoscopy at varying intervals for patients who have had previous bowel cancers or certain types of polyps removed. Colonoscopy is also performed to diagnose assess and monitor inflammatory bowel diseases such as ulcerative colitis and Crohn’s disease.


Mr Prateesh Trivedi

A colonoscopy is carried out for several reasons. As a diagnostic test, it can look for abnormalities such as bowel cancer or inflammatory bowel disease in patients who, for example, have a change in their bowel habit and/ or rectal bleeding. It can be used as a therapeutic intervention in order to remove abnormalities such as polyps. For surveillance purposes, in patients who have previously had polyps removed or had surgery for bowel cancer. It is also used for screening patients with a high risk of developing bowel cancer and as part of the national bowel cancer screening programme.

Mr Simon Radley

The procedure involves taking strong laxatives at home the day before. These are used to clear out the bowel completely so that we can get a good view when we do the colonoscopy. The laxatives and the instructions about eating and drinking are sent out to you by post beforehand.

When you come for the colonoscopy, you will have a needle in the back of your hand and we will give you a sedative for the procedure.Colonoscopy takes around 30 minutes to carry out. During this time the doctor will carefully examine the bowel both whilst passing the scope into the bowel and also whilst taking it out.

Biopsies can be taken and polyps can be removed. After a brief period of recovery you will be allowed to eat and drink. Patients are usually able to leave within a couple of hours of the procedure. Your doctor will speak to you before you go.


Mr Prateesh Trivedi
Prior to the day of the procedure the patient is given a strong laxative medication in order to cleanse the bowel to allow good visualisation. The procedure is typically carried out as a day-case procedure under sedation, but can be performed under a general anaesthetic or no sedation at all.

Mr Simon Radley

Yes there are a number of alternatives to colonoscopy. The modern alternatives are a CT scan or a virtual colonoscopy which is another form of CT scan. Neither test is as good as colonoscopy at detecting abnormalities. The other downside of these tests is that no  biopsies can  be taken nor can any  polyps be removed. We tend to use these tests only when a colonoscopy has been unsuccessful or if a patient would not tolerate a colonoscopy for other health reasons.

Barium enema was a frequently performed examination to investigate the bowel but has been virtually completely replaced by colonoscopy or CT scans.


Mr Prateesh Trivedi
The alternatives to colonoscopy are performed in the x-ray department. Barium enemas were the first choice but have now been largely superseded by CT colonography. CT colonography, however, does not reliably identify small polyps. They are utilised in situations in which colonoscopy is not safe, not possible, or when a colonoscopy is incomplete.

Mr Simon Radley

Side effects for colonoscopy are rare. The main risks of the procedure are causing bleeding or making a hole in the bowel. Bleeding is uncommon and usually only occurs when tissue is removed. You should always tell your doctor if you are on any medication to thin the blood. The most important risk is making a hole in the bowel. This usually only happens after taking biopsies or removing polyps but may also happen during a purely diagnostic examination. 


Mr Prateesh Trivedi

The medication to cleanse the bowel can be unpleasant and it is important to remain well hydrated. During the colonoscopy there is a risk of making a hole in the bowel called a perforation, and this risk is usually quoted as one in a thousand (1:1000). There is a risk of bleeding, but this typically resolves without the need for any further intervention.

Mr Simon Radley

Usually I will let you know the results as soon as you are “awake”. I can usually tell you what I have found and if I have any concerns at all. If we remove tissue (biopsies or polyps) we wont get the results back for a few days. I will usually see patients in clinic with those results.


Mr Prateesh Trivedi

The patient is given the result immediately after the colonoscopy. If biopsies have been taken, or polyps removed it can take up to two weeks to get the pathology results back.

Mr Simon Radley

My mother was a GP and from quite an early age I realised that I wanted to be a doctor. My decision to become a surgeon came early in my medical school career. I had an inspirational consultant general surgeon when I was in my third year of training. He was an old school surgeon who had seen everything and could do anything. He also had a gift for talking to patients. I wanted to be him- the surgeon’s surgeon. In those days general surgeons did most operations but things were changing. I soon realised that the days of the old fashioned surgeon were over, I would need to find my own subspecialty. Bowel surgery was the obvious choice for me, there were a wide variety of conditions to treat from piles to cancers. The operations themselves were diverse from routine, to complex and emergency procedures.

I sought out the best training posts, I went to St Marks Hospital and undertook a travelling fellowship to the USA before taking up my consultant post in one of the UKs best teaching hospitals where I have been for nearly 19 years.


Mr Prateesh Trivedi

I decided I wanted to be a surgeon when I applied to Medical School. Surgery is a fantastic specialty as it is an excellent mixture of using practical skills combined with an understanding of the basic medical sciences in order to make patients better. It is very rewarding to see patients and their families after having had, for example, a keyhole operation to remove their bowel cancer. There are new technologies developing all the time and it is exciting to keep abreast of them to offer my patients the best possible care.

Mr Simon Radley

I have had so many high points; passing my exam to become a fellow of the Royal College of Surgeons, receiving an MD from Birmingham University for my research project, being appointed as fellow at St Mark’s Hospital in London and becoming a Senior Lecturer and Consultant Surgeon at the Queen Elizabeth Hospital. Since being a consultant I have been able to take up new techniques such as laparoscopic and robotic and remain at the cutting edge of my speciality. Probably the greatest highlights come from  seeing the junior doctors who I have helped to train become consultants themselves.

Hopefully I will have made some of my own teachers and mentors proud of my achievements.


Mr Prateesh Trivedi

One of the highlights is being selected to present my research at both national and international meetings. Achieving my dream of becoming a Consultant Surgeon will always be a day I will never forget.

To find out more about a colonoscopy call us on 0808 101 0337 or make an online enquiry.

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