Bowel cancer - Diagnosis 

Diagnosing bowel cancer 

Bowel cancer - flexible sigmoidoscopy

In this video, TV presenter Lynn Faulds Wood is having a flexible sigmoidoscopy performed. This is a five-minute colonoscopy test that can detect the key symptoms of most bowel cancers.

Media last reviewed: 31/05/2013

Next review due: 31/05/2015

Bowel cancer screening

In England, everyone aged 60 to 74 who is registered with a GP is eligible for NHS bowel cancer screening.

This involves using a home testing kit to send off some samples of your stool to be tested for the presence of blood.

This can help detect bowel cancer before symptoms appear, making it easier to treat and improving the chances of surviving the condition.

Read more about bowel cancer screening.

When you first see your GP they will ask about your symptoms and whether you have a family history of bowel cancer.

They will then usually carry out a simple examination of your abdomen (tummy) and your bottom – known as a digital rectal examination (DRE)

This is a useful way of checking whether there are any lumps in your tummy or back passage. The tests can be uncomfortable and most people find an examination of the back passage a little embarrassing but they take less than a minute.

If your symptoms suggest you may have bowel cancer, or the diagnosis is uncertain, you will be referred to your local hospital initially for a simple examination called a flexible sigmoidoscopy

Flexible sigmoidoscopy

A flexible sigmoidoscopy is an examination of your rectum and some of your large bowel using a device called a sigmoidoscope. A sigmoidoscope is a long, thin flexible tube attached to a very small camera and light that is inserted into your rectum and up into your bowel.

The camera relays images to a monitor and can also be used to take biopsies (where a small tissue sample is removed for further analysis).

It is better for your lower bowel to be as empty as possible when sigmoidoscopy is performed, so you may be asked to carry out an enema (a simple procedure to flush your bowels) at home beforehand. This should be used at least two hours before you leave home for your appointment.

A sigmoidoscopy can feel uncomfortable but only takes a few minutes and most people go home straight after the examination.

More detailed tests

Most people with bowel cancer can be diagnosed by flexible sigmoidoscopy. However, some cancers can only be diagnosed by a more extensive examination of the colon. The two tests used for this are colonoscopy and computerised tomography (CT) colonography.

These tests are described in more detail below.


A colonoscopy is an examination of your entire large bowel using a device called a colonoscope, which is like a sigmoidoscope but a bit longer.

Your bowel needs to be empty when a colonoscopy is performed, so you will be advised to eat a special diet for a few days beforehand and take a laxative (medication to help empty your bowel) on the morning of the examination.

You will be given a sedative to help you relax during the test, after which the doctor will insert the colonoscope into your rectum and move it along the length of your large bowel. This is not usually painful, but can feel uncomfortable.

The camera relays images to a monitor, which allows the doctor to check for any abnormal areas within the rectum or bowel that could be the result of cancer. As with a sigmoidoscopy, a biopsy may also be performed during the test.

A colonoscopy usually takes about one hour to complete, and most people can go home once they have recovered from the effects of the sedative.

After the procedure, you will probably feel drowsy for a while so you will need to arrange for someone to accompany you home and it is best for elderly people to have someone with them for 24 hours after the test. You will be advised not to drive for 24 hours.

In a small number of people it may not be possible to pass the colonoscope completely around the bowel and it is then necessary to have CT colonography.

For more information about what a colonoscopy involves, watch this video: what happens during a colonoscopy?

CT colonography

CT colonography, also known as a 'virtual colonoscopy', involves using a computerised tomography (CT) scanner to produce three-dimensional images of the large bowel and rectum.

During the procedure, gas is used to inflate the bowel using a thin, flexible tube placed in your rectum. CT scans are then taken from a number of different angles.

As with a colonoscopy, you may need to have a special diet for a few days and take a laxative before the test to ensure your bowels are empty when the test is carried out.

This test can help identify potentially cancerous areas in people who are not suitable for a colonoscopy due to other medical reasons. A CT colonography is a less invasive test than a colonoscopy, but you may still need to have colonoscopy or flexible sigmoidoscopy at a later stage so any abnormal areas can be removed or biopsied.

Want to know more?

Further tests

If a diagnosis of bowel cancer is confirmed, further testing is usually carried out to check if the cancer has spread from the bowel to other parts of the body and to help decide on the most effective treatment for you.

These tests can include:

  • a CT scan of your abdomen and chest to check if the rest of your bowel is healthy and whether the cancer has spread to the liver or lungs.
  • magnetic resonance imaging (MRI) scan is also done for people with a cancer in the rectum to provide a detailed image of the surrounding organs

Staging and grading

Once the above examinations and tests have been completed, it should be possible to determine the stage and grade of your cancer. Staging refers to how far your cancer has advanced. Grading relates to how aggressive and likely to spread your cancer is.

This is important as it helps your treatment team choose the best way of curing or controlling the cancer.

A number of different staging systems are used by doctors. A simplified version of one of the common systems used is outlined below.

  • Stage 1 – the cancer is still contained within the lining of the bowel or rectum
  • Stage 2 – the cancer has spread beyond the layer of muscle surrounding the bowel and may have penetrated the surface covering the bowel or nearby organs
  • Stage 3 – the cancer has spread into nearby lymph nodes
  • Stage 4 – the cancer has spread beyond the bowel into another part of the body, such as the liver

There are three grades of bowel cancer:

  • Grade 1 is a cancer that grows slowly and has a low chance of spreading beyond the bowel
  • Grade 2 is a cancer that grows moderately and has a medium chance of spreading beyond the bowel
  • Grade 3 is a cancer that grows rapidly and has a high chance of spreading beyond the bowel

If you are not sure what stage or grade of cancer you have, ask your doctor.

Want to know more?

Page last reviewed: 02/09/2014

Next review due: 02/09/2016


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The 18 comments posted are personal views. Any information they give has not been checked and may not be accurate.

Manycolours said on 15 April 2014

I have just read on here that a colonoscopy feels like a snake going inside you. I have an intense phobia about snakes. So that's it, I can't have the colonoscopy now!

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wotters said on 17 March 2014

i had my first colonoscopy today was a total breeze , believe me ive worried myself to near death for the last 14months , i cancelled 3 appointments because of fear , and this was the final chance i had of gettin this done , ive spent the last 4 weeks so scared ive allmost lost my mind. i was scared of the procedure , i was scared of what they might find i was even petrified of taking the prep, but the whole thing turned out to be nothing at all ( ive had much worse time at the dentists ).
the prep (moviprep) was fine i had to drink two 1 litre batches , i was petrified something was going to go wrong or something but it was fine , i even started to panick because nothing happend for over two hours , but then the dam walls broke lol and i spent a good few hours sat on the toilet , its not nice but not scary or painfull or anything , it just becomes tiredsome , every time you think you have finished you need to go again lol bu it eventualy passed and everything was fine.
the actual procedure was a total walk in the park , it was all over and done in what felt like 5 mins , it was slightly uncomftable a few times and it made me groan a bit but trust me it was nothing , if i can go through it without any problems then anyone can do it .
havent got to go for another one untill 5 years time and i can honestly say i wont be worrying about it one little bit .
the worst bit about the whole thing is the waiting and not knowing , the actual procedure is nothing.
so please if you are reading this and are scared about the procedure take it from the biggest wimp on the planet it really is nothing to worry about .

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billybob12 said on 23 February 2014

Had my first colonoscopy yesterday and after weeks of worrying I thought I'd let other people In a similar situation know there is no need too .
I was in and out in two and a half hours and that includes tea and toast ! I chose to have sedation and felt nothing , I remember talking to the nurse and next thing I know I was being told it was all complete apparently I never went to sleep but I don't remember anything , was sent to recovery room to come round for 30 min then given tea and toast and my results then allowed to go .
So my advice is don't worry the staff are friendly and professional they do this every day and are good at it , and at the end your minds put at ease as all those weeks of worry are over .

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User524436 said on 07 February 2014

It's now 24+ hours since my first colonoscopy. I'm a 34 year old female, no children, pretty small frame, never spent a night in hospital in my life thankfully. Referred for a colonoscopy (having already had an upper GI, ultrasounds, colposcopy, xrays and a cystoscopy due to severe anaemia). I speak from personal experience, my procedure was a breeze.
The preparation wasn't nice but I struggled more with the restricted diet - I usually eat well so the list of foods was disappointing. The night before the procedure was horrid but it was more down to the hunger headache, shakes and lack of sleep. I decided before I went that I wouldn't have sedation of any sort - a surprise to the doctors who stressed that it could be painful especially for a woman of my build (at my hospital, around 1% of patients in total go 'awake', less still for women). Having had a cannula, I could have changed my mind at any point which was reassuring. I was laid down on my left side, had a probing finger up my bum, told to relax, break wind whenever I felt and reassured constantly. In went the camera and I shut my eyes...Whenever the doctor was approaching a bend, he told me, I held my breath, felt the turn and released my breath - mind over matter! Yes, a couple of times, I held my breath and scrunched up my nose but when asked, I described the discomfort as mild throughout. I took only fleeting glances on screen, seeing as I have photographs to give my GP, there's something for the family album! It felt exactly as I expected, like a snake was going through my insides.
If you feel embarrassed, don't worry - you don't know these people, they don't spend ages looking at your bum, they don't mind how you behave.
No sedation = no need to stick around except to have your BP/pulse taken. I was free to drive and operate heavy machinery;-).
Everyone is different, you won't all require sedation, you won't all suffer with the prep, you won't all experience pain. Relax, it's for the greater good!

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janman said on 27 January 2014

hi iv been bleeding from my anus now for over 10 weeks with cronic abdo pain and every time i go toilet i pass blood clots and mucus iv had a ct scan nothing showed up except a cyst on my liver im still worried anyone help

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Anonymous said on 16 January 2014

Seen surgeon to day he has booked me in for a colonoscopy and endoscopy in a few days. The more I read about other peoples experiences the more I feel sick :( I know it has to be done.

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Inspired13 said on 31 December 2013

Why isnt there any mention that sometimes a general anesthetic will be required for the sigmoidoscopy, sedation is not always suitable.

It happens quite a lot but not a mention of it here, everyone would expect that they could get this test done and be over with in less than an hour when that isnt always the case.

If youre going to give out information then do it properly. It is not rare so why isn't it mentioned.

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MPeth said on 27 November 2013

I had my first colonoscopy 12 years ago I was aged 55 (symptoms being blood in the poo) and I am so glad I did. It turned out that they found a tumour which was cancerous and was removed within a month of diagnosis. If I hadnt gone through the procedure I would not be here now to tell the tale. I had my 4th colonoscopy last week. OK so you lose your dignity for half an hour or so and you may experience a little discomfort but if it saves your life what the heck. When I first saw my Consultant I said I wish you were looking down my throat but he said "that would be boring"!!! The only other comment I would say is take the Picolax laxative if you can. Only needs to be diluted in 150 mg of cold water. So easy to take.

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Seasidebelle said on 16 May 2013

I had my colonoscopy today. Having read comments on here I was terrified. There was no need to be! Yes, it is a bit uncomfortable at times, but nothing to worry about. I wasn't sedated, I was totally aware of what was happening, I chatted with my consultant and two lovely nurses held my hands. When the camera was being removed I watched the procedure on the screen. I am a lady in my late fifties and I am not brave, I am terrified of the dentist. I would have another colonoscopy rather than have a tooth out! Please, if you have to have a colonoscopy yourself, don't let comments on here frighten you to death. The worst part was missing food for a day and sitting on the loo after the laxative,

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Kiwiman said on 07 May 2013

To those who say they are traumatised by reading the description of the diagnostic procedures. They are usually either pain-free, or involve a little discomfort bordering on a little bit of pain.
Trust me dealing with cancer (and in fact your loves ones dealing with it) makes facing a little embarrassment and discomfort a holiday by comparision. If you can't do it for yourselves do it for your loved ones. No excuses folks. We're all adults.

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dipsydiver said on 22 April 2013

Having read the comments to date I'm afraid I have not enough confidence to go ahead with my colonoscopy in 3 weeks time. I think that had it happened when I first became ill around 12 weeks ago I think I would have been fine but after a short spell in hospital to be given antibiotics via IV and rather off hand treatment by the consultant I was allocated I really don't think I can talk to anyone about my fears and phobias regarding the colonoscopy. I searched on line hoping to ease my worries but it has made them worse and as a result I am going to cancel my appointment. I have a fairly good immediate supply of pain relief and will hope my gp who I also find difficult to talk to, will continue to provide the prescriptions for them.
I really cannot face the colonoscopy.

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Poppsue3 said on 21 April 2013

I had this procedure on 19/04/13 @ Ipswich Hospital. Need not have worried, everyone was so kind & really put me at ease. Being the coward I am I opted for sedation & was informed I could watch it all happening on screen or just close my eyes. Think I was so wiped out from the Klean-Prep which also made me nauseous that I don't remember anything until being brought out to recovery. The nurse said I was probably slightly dehydrated with having D&V. After short recovery time a nice really welcome cup of tea & some toast (if coeliac like me take snack with you) my husband was phoned to fetch me. Cannula removed & all checks finished I was told the outcome etc. & discharged, although very tired I was absolutely fine. Thanks everyone fantastic. Worst part is prep. It made me personally feel dreadful.

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Janej said on 15 December 2012

I made this account because i had previously read Judy's post and was terrified of this procedure. I am a hospital phobic - Second generation infact. And i was so scared i was tempted to say no and that i simply couldn't do it. Only the thought of how much deeper in trouble i could be in if i didn't go through with it forced me to go.

I had it done four hours ago! Honestly, it was a breeze. Mildly uncomfortable and for a matter of seconds it felt like i had a bad stomach ache at one point. But before i knew it it was all over

Back in the room and i had a cup of tea and some bikkies and i was off home. Still a bit sedated i guess but good to go.

Everyone at Hinchingbrook hospital was very nice and they make sure your modesty is preserved as much as possible.

The purge before hand is the toughest thing, all that not eating! I feel absolutely fine now, no pain or soreness.

So if you have this procedure scheduled please do not be afraid. Really, it is not that bad. I cannot tell you how much i was dreading it. Relax about it and you'll be just fine.

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duncs21uk said on 20 July 2012

LeeApp - I hope your pocedure went ok. I am due to have a colonoscopy next week and i am terrified. I'm scared of hospitals (can't even watch medical programmes on TV). I feel that scared that i'm almost at the point of phoning the hospital and cancelling the appointment.

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DDDenisDean said on 15 April 2012

Sorry for the double post, the first one disappeared.

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DDDenisDean said on 15 April 2012

I had a colonoscopy last week and I can honestly say the worst part of it was drinking the prep liquid.
Went into hospital at 1630, had the procedure at 1800 which I would call uncomfortable, certainly not painful.
Perhaps I was lucky and had a good endoscopist.
Back in the ward before 1900, had tea and coffee and a sandwich and on my way home by 2030.
I did experience constipation for two days after but solved this with a laxative.
I too was terrified of the procedure.
LeeApp, my best wishes go with you and I can honestly say if I had to go thought it again, which I probably will due to being unable to reach one growth, I shall have no fear of it.
Think of it as a necessary evil, an embarrassment, maybe, but if it can sort your problems out, it is worth it.

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LeeApp said on 31 March 2012

I just came across this comment on colonoscopies. I am scheduled for one in three weeks (diarrhoea for over three months that has turned suddenly into constipation plus numerous symptoms of ovarian cancer), and after reading this, I am even more petrified than I was before. I've spoken with many people who have assured me that it's a breeze and even went so far as so talk with the endoscopy until manager sister who showed me the scope and talked to me about the pain and what is used. So I have options: do it and it turns out fine or do it and if it's painful, abandon. I just can't stand being this scared for the next three weeks. We're talking about a major phobia and non-functioning scared here!!!!!! This comment makes me want just to run as far away and as fast as I can now. I've had previous abdominal surgery for endometriosis that the gastroenterologist said could cause pain.

If a general anaesthetic was an option, the wait would even worse. What the h*ll do I do now??? I am absolutely scared beyond belief!!!!!!!!!

Please HELP!!!!!

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JudySR said on 18 January 2012

RE colonoscopies, there is no mention of the excrutiating agony of this procedure, which I have now experienced twice. If you review your own page of comments you will see that I am not alone and I'm alarmed that people aren't warned of the terrible pain. My procedure had to be halted, even though I was given sedation. I have given birth to two babies without any pain relief and used the breathing and relaxation techiniques but to no avail. Patients should be warned about this aspect of colonscopies and offered (as I now have) a general anaesthetic, which, incidentally, a nurse who was a patient said she had had because she knew how awful the pain could be.

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