A colonoscopy is a test which allows me to look into your large bowel or colon and often, the end of the small bowel or terminal ileum. The last part of the colon leads into the rectum where faeces (stools or motions) are stored before being passed out from the anus. A colonoscope is a thin, flexible, telescope. It is about as thick as a little finger. It is passed through the anus and into the colon. The colonoscope contains fibre optic channels which allow light to shine down so the operator can see inside your colon. The colonoscope also has a ‘side channel’ which allows different devices to be passed. For example, I may take a small sample (biopsy) from the inside lining of the colon by using a thin ‘grabbing’ instrument (forceps).

Why is colonoscopy performed?

A colonoscopy may be advised if you have symptoms such as bleeding from the lower bowel, diarrhoea, pains in the lower abdomen, for investigation of anaemia or a strong family history of bowel cancer.

A colonoscopy is often normal, but a normal result is still useful to exclude certain conditions.

What happens during colonoscopy?

Colonoscopy is usually done as a day case. It is a routine test which is commonly done. You will usually be given a sedative to help you to relax. This is usually given by an injection into a vein in the back of your hand. The sedative can make you drowsy but it does not ‘put you to sleep’. It is not a general anaesthetic.

You will be asked to put on a gown or shorts that open at the back. While you’re resting on your left side, I will gently examine your back passage with a gloved finger and then carefully insert the colonoscope into your rectum. Lubricating jelly will be used to make this as easy as possible.

Air is then usually pumped through the colonoscope into your colon to make it expand and to make the bowel wall easier to see. This may cause a feeling of pressure, bloating, or cramping during the procedure. It is normal if you get an urge to go to the toilet or pass wind. The procedure is usually well tolerated but rarely may cause more severe pain or discomfort. I may use more sedation or ask you to change position if this occurs.

A camera lens at the end of the colonoscope sends pictures from the inside of your bowel to a monitor. I will look at these images. If necessary, I will take a biopsy and/or remove any small growths or polyps you have. This is done using special instruments passed inside the colonoscope and shouldn’t cause you any pain.

What preparation is required?

The colon needs to be empty so that I can get a clear view. You will be instructed on how to take a special diet and very powerful laxatives (usually Movicol or occasionally KleenPrep) either the day or morning before the test. WKG will provide written instructions when booking the colonoscopy.

A colonoscopy usually takes about 20-30 minutes but expect to be in hospital for 3-4 hours to allow time for a nurse-led assessment on arrival and for time to recover following the procedure.

What happens after colonoscopy?

You will be monitored in the recovery area for 15-30 minutes until the effects of the sedatives start to wear off. Normally you will be offered a drink and a light snack once you are fully awake (about 30-45 minutes after the colonoscopy). You may have some mild cramping or bloating from the air that was placed into the colon during the examination. This should quickly improve with the passage of flatus.

I will come and see you before discharge to inform you of the results and to answer any questions that you may have. I shall write, usually 5-7 days later, with the results of any samples taken during the procedure.

Sedatives will affect your judgment and reflexes for the rest of the day. You should not drive, operate machinery, drink alcohol or make legal decisions for 24 hours after having the sedative. You will need somebody to accompany you home and to stay with you until the effects have fully worn off. Most people are able to resume normal activities after 24 hours.

Special monitoring

You will need to have blood tests (full blood count, liver & kidney function) about 3 months after starting drug and then after each year because of the drug’s rare adverse effects on the bone marrow (it suppresses production of white cells & platelets) and kidney damage (interstitial nephritis). If the blood tests become abnormal, your doctor will advise you to stop the drug and normally, the test results return to normal.

At Digestive Health City & Docklands, we work hard to provide our patients with top-class care. You will enjoy friendly, fast and modern treatment by a highly experienced gastroenterologist. We carefully review patient satisfaction and feedback, and at Digestive Health we are continuously making improvements to our services, ensuring the highest level of care possible.

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@dradamharris - 2 weeks

Was pleased to organise and speak at the 3rd annual “Update in Medicine for GPs” event that took place on Saturday…

@dradamharris - 5 months

Listen to my podcast on Helicobacter pylori at

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