Nearly 40,000 cases of bowel cancer are diagnosed in the UK each year, making it the third commonest diagnosed cancer ⁽¹⁾. Around 14,000 ⁽¹⁾ of these cases are located in the rectum, with the rest in the colon, which is why the disease is referred to as colorectal cancer.

If bowel cancer is diagnosed at an early enough stage and treatment is received in time, the outcome can be extremely positive.

Why is a colonoscopy necessary?

A colonoscopy is a test to find out what is causing symptoms, such as pain in your lower abdomen, bleeding from the anus, inflammation, persistent diarrhoea and other changes in bowel habits. These symptoms may indicate early signs of bowel cancer.

Other conditions diagnosed by a colonoscopy include Crohn's disease, ulcerative colitis and diverticulitis (pouches that form in the lining of the colon).

The colonoscope is a narrow, flexible telescope, as thick as your little finger. Inside the tube is a side channel that illuminates the lining of your bowel. Another side channel relays pictures back to a television monitor.

A third channel permits the endoscopist (or colonoscopist) carrying out the procedure to pass surgical tools down the colonoscope and take a biopsy (small tissue samples), or remove polyps (growths) to send away for testing in a laboratory.

What's the difference between a sigmoidoscopy and a colonoscopy?

During a sigmoidoscopy, doctors view only the final part of the colon, while a colonoscopy allows an examination of the entire colon.

A sigmoidoscopy is often a screening procedure to see if a full colonoscopy is actually needed and is also performed in conjunction with a faecal occult blood test (FOBT) to detect the presence of blood in stools.

What are they actually looking for?

The doctor uses the colonoscope to examine the lining of your colon for the presence of inflammation and any abnormal growths, such as polyps, which are protrusions in the bowel lining. They are mostly non-cancerous but can sometimes develop into cancer.

How do I get ready for a colonoscopy?

Your bowel needs to be completely empty before the procedure, which means you will need to change what you eat and then take a laxative before you undergo the procedure.

The nurse or doctor will give you a detailed instruction sheet telling you what you can eat and when to take the laxative. For example, two days before the colonoscopy, you will need to change to a low-fibre diet and increase your intake of liquids. One day before, you should eat no solid food and only drink clear liquids (no milk or soups).

The laxative is strong, so you will need to be near a toilet after you take it. Keep some wet wipes and moisturising cream to hand as your bottom can become quite sore.

Follow the instructions carefully, because if your bowel is not completely empty, the doctor won't be able to see the colon clearly and the procedure may need to be postponed to another time.

What happens during the colonoscopy itself?

A colonoscopy is usually an outpatient or day case, which means you can go home once you have recovered from the procedure.

The endoscopist will ask you to lie on your side and inject a sedative and painkiller into a vein in the back of your hand. You may also be given a muscle relaxant.

The sedative will make you feel relaxed and drowsy, but you won't be totally unconscious, as you would be with a general anaesthetic. You also won't remember much about the procedure afterwards.

The colonoscope is gently inserted into your anus and up into the colon. Gas is passed into the colon to expand it, which makes the lining easier to see. You will feel as though you need to go to the toilet or pass wind, but this is entirely normal. There is absolutely no need to feel embarrassed if you do pass wind, as the endoscopist will expect this to happen.

As the colonoscope progresses along the bowel, it must navigate the natural bends. You may feel some discomfort, but this is temporary. The endoscopist will remove any polyps or take tissue samples if necessary during this time, but you will not be able to feel anything.

The whole colonoscopy procedure takes between 30 and 40 minutes, after which the endoscopist will gently remove the device and then send any tissue samples to the laboratory.

What happens to me afterwards?

You will be put in the recovery ward to rest for as long as you need to - normally one to two hours, maybe longer if you have had tissue removed.

The endoscopist may discuss the results of the procedure based on the initial examination, but if you are still recovering from the effects of the sedative you are unlikely to remember what is said, so you should have someone with you.

You will need someone to pick you up, if you have had a sedative, as the drugs will stay in your blood system for about 24 hours. You must not drive, operate machinery or drink alcohol for 24 hours.

How long will I have to wait for the results?

The results of the laboratory tests will be sent to your GP or consultant within a week or so. A report of the colonoscopy will also be sent to your GP or consultant. At your follow-up appointment, you can find out if you need any further procedures or medication.

What are the side-effects of a colonoscopy?

Apart from feeling sleepy or tired for several hours afterwards, you may also feel bloated because of the gas used during the procedure to expand your bowel lining. This will gradually subside as you expel the gas in the natural way.

If the endoscopist removed a polyp or took a tissue sample, you may see a small amount of blood in your first bowel movement following the colonoscopy.

Complications from the procedure are uncommon, but can include damage to the lining of the colon or, in rare cases, the bowel might have been perforated. If you experience abdominal pain which gets worse, fever, or if you pass a lot of blood from your anus, contact your doctor immediately.

Infolink:

• Beating Bowel Cancer