Colonoscopy

Introduction

A colonoscopy is a medical procedure used to look inside your colon, which is sometimes called the large intestine or large bowel. The colon is the lower part of your intestine. It joins the small intestine at a place called the caecum and ends at the rectum where faeces (or stools) are stored before being passed out of the body.

A colonoscopeis a narrow, flexible, tube-like telescope, about the thickness of a little finger. Within the tube is a side illumination channel that sheds light on to the lining of your bowel and another, which relays pictures back to a television monitor.

A further channel allows devices to be passed through the colonoscope, which the endoscopist (the medical practitioner carrying out the colonoscopy procedure) can use to take small samples of tissue (a biopsy), or remove polyps (growths) for testing in a laboratory.

Why do I need a colonoscopy?

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

Bowel cancer is the third commonest cancer after breast and lung cancer, with approximately 36,000 cases diagnosed in the UK each year.  Nearly 14,000 of these cases are located in the rectum (back passage), with the rest in the colon. If bowel cancer is diagnosed early enough and you get treatment in time, it is has an excellent treatment outcome.

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

What is a Sigmoidoscopy?

The difference between colonoscopy and sigmoidoscopy is related to which parts of the colon each can examine. During a Sigmoidoscopy, doctors view only the final part of the colon, while a colonoscopy allows an examination of the entire colon.

Often a sigmoidoscopy is used as a screening procedure to see if a full colonoscopy is necessary. In many instances, a sigmoidoscopy is performed in conjuction with a faecal occult blood test (FOBT), which is a test to detect the presence of blood in stools.

What does a colonoscopy look for?

A colonoscopy allows the doctor to examine the lining of your colon for the presence of inflammation, polyps and any abnormal growths. Polyps are protrusions from the lining of the bowel. They are usually harmless but can sometimes turn into cancer.

Preparing for a colonoscopy

In order to have a clear view of your bowel, it needs to be empty, which requires dietary changes and a laxative before you have the colonoscopy. You will be given a detailed instruction sheet covering your diet and when to take the laxative.

Two days before the procedure, you will need to change to a low-fibre diet, which means avoiding foods, such as wholemeal bread, while increasing your liquid intake. One day before, you should have no solid food and drink clear liquids only (no milk or soups).

You will be given instructions on when to take the laxative, which is quite strong, so you need to ensure you are close to a toilet when you take it.

It is very important to follow the instructions carefully, because if your bowel is not completely empty, the doctor may not be able to see the colon clearly and the colonoscopy procedure may have to be repeated.

What happens during a colonoscopy?

A colonoscopy is usually done as a day or outpatient case, which means once you have recovered from the procedure, you will be able to go home.

You will be asked to lie on your side and will be given a sedative and a painkiller, which is usually administered into a vein in the back of your hand. Unlike a general anaesthetic, a sedative will make you feel relaxed and a little drowsy, but you won't be totally unconscious. You may not remember much about the procedure afterwards, however. You may also be given a muscle relaxant.

The colonoscope is gently inserted into your anus (back passage) and up into the colon. Air is passed into the colon to make the lining easier to see. This may make you feel as though you need to go to the toilet and also make you feel bloated and want to pass wind. This is entirely normal and there is no need to feel embarrassed if you do pass wind, as the colonoscopist will expect this to happen.

As the colonoscope passes along the entire length of your colon, there are some bends that naturally occur in the bowel. Negotiating these bends may feel uncomfortable, but the discomfort is temporary. If polyps or tissue samples need to be removed for testing in the laboratory, this is done by an instrument attached to the colonoscope and is painless.

The whole procedure takes between 30 and 40 minutes, at the end of which the colonoscopist will gently remove the colonoscope.

What happens afterwards?

You will be allowed to rest for as long as necessary. This is usually one or two hours, possibly longer if you have had a polyp removed.

The doctor or colonoscopist may discuss the results of the procedure based on their examination. However, if you are still recovering from the effects of the sedative you may not remember what is said, so it is a good idea to have someone with you.

The sedative will stay in your blood system for about 24 hours, so it is important that you have someone to accompany you home and to stay with you until the effects have worn off. It is also important not to drive, operate machinery or drink alcohol for 24 hours.

When will I know the results?

If you have had a polyp or tissue sample removed, this will be sent to a laboratory for testing, the results of which 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 discuss if any further procedures or medication are needed.

Are there any side effects?

You will probably feel sleepy or tired for several hours afterwards, which is caused by the sedative. You may also feel bloated and have slight pain or discomfort due to trapped wind as the air used during the procedure gradually leaves your colon. If you have had a polyp or tissue sample removed, you may have a small amount of blood in your first bowel movement following the colonoscopy.

Complications are rare, but can include damage to the lining of the colon following removal of a polyp, or perforation of the bowel. If you experience abdominal pain which gets worse, fever, or passing a lot of blood from your anus, consult your doctor immediately.

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