Colonoscopy: The operation

Colonoscopy: The operation

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Before you agree to have your colonoscopy examination it is important to know all you can about it. The information here is a guide to common medical practice. Each hospital and doctor will have slightly different ways of doing things, so you should follow their guidance where it is different from the information given here. Because all patients, conditions and treatments vary it cannot cover everything. Use this information when making your choice of colonoscopy examination with your doctors. You should mention any worries you have. Remember that you can ask for more information at any time.

What is the problem?

Your doctors suspect a problem in your large bowel may be the cause of your symptoms. These symptoms can include pain in the abdomen, bleeding, a change in your regular bowel habits (such as continued diarrhoea) or a lump felt in the abdomen. We need to do the colonoscopy examination to find the cause.

What is a colonoscopy?

A colonoscopy is a test to look inside the large bowel, colon meaning large bowel and -oscopy meaning looking into. The examination is done through the anus using a long flexible telescope, called an endoscope, which is slightly thicker than a pencil. The endoscope lets the doctor see the inside of the bowel and any problems. Air is blown into the bowel to make it expand so the doctor can see the lining better. The endoscope is also called a colonoscope.

What is the large bowel?

The large bowel is part of the gastrointestinal tract, which extends from the mouth to the anus. The gastrointestinal tract digests the food that you eat and gets rid of the waste. The large bowel is involved with the disposal of waste products from the body. The bowel is also called the intestine or gut. The large bowel is the lower part of your bowel, beyond the appendix. Above the appendix, up to your stomach, the bowel is narrower and is called the small bowel.

What has gone wrong?

There are many conditions that can happen in the large bowel, including:

  • Irritable bowel syndrome - One of the most common causes of large bowel symptoms is irritable bowel syndrome (IBS). Here, the bowel muscle loses its smooth, peristalsis action and goes into cramps. This can cause pain, swelling of the abdomen, diarrhoea and a discharge of mucus.
  • Diverticular disease - In diverticular disease there are pouches in the bowel lining, through the muscle wall. These pouches may become infected. An infected pouch may cause a hole through the bowel, called a perforation, or cause a narrowing the bowel, called a stricture
  • Inflammatory bowel disease (IBD) - This is an inflammation of the lining of the bowel, also called colitis.
  • Polyps - These are lumps on the inside of the bowel and can cause bleeding. Polyps are best removed because even though they are not cancer they can become cancerous over time. A colonoscopy is sometimes used to check that more polyps have not formed in patients who have had polyps removed in the past.
  • Cancer - There may be a tumour or cancer. Most people who have a colonoscopy do not have cancer. Colonoscopies are also used to check the bowel in patients who had previous treatment for bowel cancer or a family history.

The large bowel is about 140cm (5 feet) long. It starts in the right side of your abdomen, where it is called the caecum. It runs in a large loop round the abdomen and down into the pelvis as the colon. Deeper in the pelvis it is called the rectum, where it opens onto the skin at the anus.

You should ask your doctor to explain why he feels you need a colonoscopy.

The aims

The aim of the examination is to find out what is happening in the large bowel to cause the symptoms you have. This means that the correct treatment can be given for your condition.

The benefits

The colonoscopy gives a direct view of the lining of the large bowel, compared with just shadows seen on a barium enema x-ray.

If we suspect irritable bowel syndrome is the cause of your symptoms we do not expect to see anything abnormal, because the cramped muscle does not show up during this examination. The examination can be used to check there is nothing else apart from the irritable bowel.

During the colonoscopy we can take small samples of the bowel lining, called biopsies, for examination under the microscope. We can also remove polyps, if any are found.

The large bowel may be seen to be normal, but there is a small chance of missing a condition, as the colonoscopy is not fail proof.

Are there any alternatives?

You will probably have a series of tests to find out what is causing your symptoms. For example, you may have a barium enema. A liquid that shows up on x-rays, called barium sulphate, is passed into the bowel through the anus. A series of x-rays are taken from different angles to show up as much of the bowel as possible. If the barium enema showed you had a polyp, you may then have a colonoscopy to have it removed.

There is another examination, similar to a colonoscopy, called a sigmoidoscopy. The endoscope used here is shorter and your doctor may recommend this test if he thinks, for instance, that any bleeding is coming from a haemorrhoid or a polyp a short way up your bowel.

There are tests of your stools that can be done to check for bleeding, such as the faecal occult blood test.

What if you do nothing?

If you have symptoms, such as blood in your stools, they should be investigated, as leaving things as they are can be very risky. You may be missing out on important treatment.


Submit a request for further information, a quotation or indicative cost. Your enquiry will be forwarded to up to 3 private healthcare providers. They will respond directly with further information.

Get a quote for a bowel cancer screen >



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