Tests for bowel cancer

These tests are called sigmoidoscopy and colonoscopy. Sigmoidoscopy examines the rectum and lower part of the bowel. Colonoscopy examines the whole of the inside of the bowel. There is information about having a colonoscopy in the Diagnosing colorectal cancer section of CancerHelp UK.

Some bowel cancer specialists are convinced that examining everyone for pre-cancerous polyps just once could dramatically lower the number of bowel cancer cases. Sigmoidoscopy is more likely to be used as a general screening test for bowel cancer than colonoscopy. This is because it is a quick and simple test taking less than 15 minutes and you do not need any kind of sedative or painkiller. Colonoscopy takes longer (about an hour) and you are usually given a sedative beforehand to relax you and make you drowsy.

A large trial has finished recruiting and screening people using sigmoidoscopy in a one-off test at around 55-60 years old. Removing potential cancers and early cancers at this age could prevent some people from ever developing invasive bowel cancer. So if this screening programme is successful, it could save a lot of distress as well as saving money on treatment.

Having a sigmoidoscopy

Sigmoidoscopy involves putting a thin, bendy tube into the back passage. The tube has a camera on one end and is connected to a TV screen so that the specialist and the team can see inside the bowel. The doctor can look at the bowel wall and see if there are any polyps (growths) that could develop into cancer. If there are, they can be snipped off straight away. This test is usually painless or only mildly uncomfortable.

To have a sigmoidoscopy, you must have an empty lower bowel. You are given a small enema or strong laxatives to clear it out. In the recent trial an enema was sent to those taking part, so that they could use it in the privacy of their own homes before they went to the hospital to have their sigmoidoscopy.

Once at the hospital, you may be asked to change into a hospital gown. Then, you will be asked to lie on the couch on your left side. The doctor will put some gel onto the end of the sigmoidoscope and slide it gently into your back passage. Then the doctor will move it slowly further in. This is usually painless, but if you find this too uncomfortable at any stage, just tell the doctor and he or she will stop. Once the tube is in, a little air or carbon dioxide is pumped into your bowel. This inflates the bowel slightly and helps the doctor to see the bowel wall more clearly. If you have any small polyps, the doctor will snip these off and send them away to be examined under a microscope. The whole thing takes about 5 minutes. It will take a little longer if you have to have polyps removed, but even then the test only takes about 10 - 15 minutes.

Once the test is over, you can go home. Some people have a small amount of bleeding after this test, particularly if they have had polyps removed. This is normal and usually clears up on its own. Before you leave the hospital, you should be given a number to ring in case you are worried about the amount of bleeding or if any bleeding continues for more than 4 days.

The stool test is sometimes called the 'faecal occult blood test' or FOB for short. Occult means hidden. So the FOB test is for blood hidden in the stool. It can pick up minute traces of blood that may be too small to notice.

Bleeding is often an early sign of a bowel cancer. But it can also be a sign of many other things, such as piles. So these tests can be positive when you don't have cancer. This is called a false positive result. You may also get a false positive result because you have eaten something that reacts with the test kit. For example, you may have had red meat or red wine or taken some iron tablets.

The other problem is that an early bowel cancer may not bleed all the time. So you could get a false negative (no blood in your stool sample) when there is a cancer in the bowel.

If a test is to be used to screen people throughout the country, it must be reliable. Otherwise it can cause

• Unnecessary medical investigations
• Unnecessary anxiety
• Undetected cancers to get to an advanced stage before they are found

Pilot studies have looked at screening in small areas of the UK. The type of testing being used in the pilot studies involved putting a stool sample onto a piece of card and sending it back to the researchers. The pilot studies reported in July 2003 and recommended that screening for bowel cancer is introduced across the UK. A national bowel cancer screening programme is being phased in over 3 years, from 2006. Men and women aged between 60-69 years old will be offered an FOB test every two years. There is more about this screening programme on the screening for bowel cancer page.

The pilot studies in Coventry and North Warwickshire have been extended so that the researchers can find out more about the long term gains and drawbacks of this type of screening programme. If you are between 58 and 69 and are registered with a GP in either of these areas, you will be invited to take part.

If you want to try stool testing, we recommend that you talk this over with your GP. But there are test kits available to buy from chemists in the UK. These vary and so you should follow the instructions for the particular kit you buy. This may include changing your diet for a few days before you use the kit.