Colonoscopy

If you have a second or third unclear FOB test|, or an abnormal result, you will be given an appointment to see a specialist screening nurse. The appointment will be at your local hospital or screening centre and should be within a week of the letter telling you the FOB test result.

The practitioner will explain what your result means and answer any questions you may have. They will discuss having a colonoscopy and give you a detailed explanation of the procedure, and what the benefits and risks are. They will also assess whether you are fit to have a colonoscopy.

A colonoscopy isn’t appropriate for everyone. If you are not able to have a colonoscopy, you may be offered a different investigation, such as a barium enema| or CT colonography|.

The procedure is usually done in the hospital outpatient department and takes about an hour. It's the most thorough and effective way of diagnosing bowel cancer|. The colonoscopy can also see if there are any polyps in your bowel.

The bowel has to be completely empty for a colonoscopy. This means following a careful diet for a few days before your test. You’ll also need to take laxatives, which the screening centre or hospital pharmacy will provide. The department carrying out your colonoscopy will give you instructions about your diet, and about exactly when to take your laxatives.

Just before the colonoscopy, you may be given a sedative tablet to help you feel relaxed. Once you’re lying comfortably on your side, the nurse or doctor will gently pass a thin flexible tube (a colonoscope) into your back passage. The tube is made up of flexible fibres. It can easily pass around the curves of the bowel so that its lining can be examined. A tiny light and camera on the end of the tube are used to show any abnormal areas.

During the colonoscopy, photographs and samples (biopsies) of the cells on the inside of the large bowel can be taken. Most polyps can be painlessly removed using a wire loop that is passed down the colonoscope. A colonoscopy can be uncomfortable, but the sedative will help you feel more relaxed.

The colonoscopy should take 30-45 minutes. Most people are ready to go home a couple of hours after their test. You’ll need to arrange for someone to collect you from the hospital as you shouldn’t drive for several hours after a sedative. You should also have someone with you for about 12 hours afterwards.

For most people a colonoscopy is a straightforward procedure and they will have no side effects. Rarely however, complications can happen, including: 

Fluid loss

Taking laxatives before having a colonoscopy may sometimes cause you to lose a lot of fluid from your body, as you pass several bowel motions. If you have heart problems, let your GP know before you take any laxatives as this fluid loss can temporarily worsen your condition.

Breathing or heart problems

Some people react to the sedative that is used during a colonoscopy. This can cause temporary breathing or heart problems. It’s rare to have a serious problem and you’ll be monitored during the colonoscopy.

Not being able to see the whole bowel

Sometimes it’s not possible to see the whole bowel during a colonoscopy. This can happen if the bowel isn’t completely empty or if the colonoscope can’t pass round a bend in the bowel to reach the end. If this happens, you may be asked to have another colonoscopy, or a barium enema.

Heavy bleeding

About 1 in every 150 people who have a colonoscopy will have heavy bleeding afterwards. If tissue samples (biopsies) are taken or polyps removed there is a risk that the area may bleed. If you notice a lot of bleeding, contact the screening centre as soon as possible for further advice.

A perforated bowel

Rarely the colonoscope can make a hole (perforation) in the wall of your bowel. This happens to about 1 in 1,500 people who have a colonoscopy. If your bowel is perforated you may need an operation to mend the hole.

Risk of death

In extremely rare cases, a person may die as a result of having a colonoscopy. This is very rare and only happens in around 1 in every 10,000 colonoscopies. The benefits of having a colonoscopy far outweigh this risk.

The specialist doing your colonoscopy will tell you if they have removed any tissue samples (biopsies) or polyps from your bowel. If samples have been taken, you will have to wait up to three weeks for the results. This can be an anxious time for you and it may help to talk things over with a close friend or relative or a support organisation|.

The possible results you could get include:

• a normal result
• benign polyps
• other benign causes, such as inflammatory bowel disease
• a cancer.

Normal result

This means that no polyps or cancer have been found in your bowel. About half of people who have a colonoscopy will get a normal result.

There is a small chance that the colonoscopy may miss a cancer, so a normal result doesn’t guarantee that you don’t have cancer, or won’t develop it in the future. If your colonoscopy was normal you’ll be offered bowel cancer screening again in two years.

Benign polyps

If one or more polyps are found during your colonoscopy they can usually be removed at the same time. This is known as a polypectomy and it can help to prevent bowel cancer developing. Around four in ten (40%) of people who have a colonoscopy following an abnormal FOB test will be found to have polyps. In some cases, polyps may come back again after surgery.

The removed polyps will be looked at in the laboratory and, depending on the results, you may be invited to have another colonoscopy. This will usually be in one or three year’s time, or you may simply continue with your two-yearly bowel cancer screening.

Other benign causes, such as inflammatory bowel disease

If your colonoscopy results show that you have inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis, you’ll usually be referred to a gastroenterologist, a doctor who specialises in these conditions.

Cancer

Only very few people (about one in ten, or 10%) who have a colonoscopy after an abnormal FOB test will be diagnosed with bowel cancer. If a cancer is found, you will be referred to a cancer specialist for treatment.

If cancer is found at its earliest stage, there is a very good chance of curing it. About nine out of every ten (90%) early stage bowel cancers can be successfully treated. However, not all bowel cancers that are found by having a colonoscopy can be cured.