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If the results of your bowel screen home test are not normal, you will need to have another, more detailed test called a colonoscopy.

A colonoscopy is an examination of your bowel using a small camera on the end of a thin flexible tube. The tube is inserted into your bottom, passed through the rectum into the large bowel.

The colonoscopy is a day procedure, (not requiring you to stay overnight). It is usually performed in a hospital endoscopy unit.

During the examination a small sample of the lining of your bowel may be taken to look at more closely. This is called a biopsy. The test looks for any polyps or signs of disease in the lining of your bowel.

Polyps are small growths that are not cancer but, if not removed, might turn into cancer over time. If polyps are found they are usually removed during the colonoscopy. This is to reduce the risk of cancer developing. This is painless.

A colonoscopy is the best way to diagnose bowel cancer and other conditions. 

Before your colonoscopy

If you can’t make it, call to cancel your appointment. We can then offer your appointment to someone else on the waiting list. Another appointment can be arranged for you. 

For your colonoscopy examination your bowel needs to be fully cleared out. You will be given a laxative and dietary instructions. Follow all instructions given to you for your test to prepare your bowel for the colonoscopy.

It is very important that your bowel is fully cleared out so that your colonoscopy can be as successful as possible. If it is not, your colonoscopy may have to be rescheduled.

Contact the endoscopy unit before taking your bowel preparation if you have an Ileostomy. This is when a stoma is made from the small bowel. You should also let the endoscopy unit know if you are taking blood thinning medications such as aspirin or warfarin. 

If you have had previous problems with fasting or sedation please let the nursing staff know before or when you arrive for your appointment.

On the day of your colonoscopy

Don't take any solid foods or liquids until after your examination. You shouldn't bring any valuables with you to the unit. 

You should have a shower or a bath on the morning of your examination. Bring a dressing gown with you.

It's important that you bring a family member or friend to bring you home after the procedure. You cannot leave the unit alone. Bring your medical insurance details or medical card with you.

When you arrive at the Endoscopy Unit

  • Check in at the hospital or Endoscopy Unit reception.
  • There may be a delay before your procedure so you might like to bring something to read.
  • You will be brought to a cubicle where you will be asked routine questions and have any of your own questions answered.
  • You will then change into a gown and modesty pants.
  • Identification bands will be applied to your wrists and an allergy band if you need one.
  • You will remain in the cubicle until you are brought to the procedure room.

Due to the unpredictable nature of the emergency workload in the hospital, it is not always possible to keep to the scheduled times. This may affect how long you will be waiting on the day.

In the procedure room

Once you are on the trolley the staff nurse will measure and document your blood pressure, pulse and oxygen levels. You will also be attached to the cardiac monitor.

A member of the medical team will discuss the procedure with you and ask you to sign a consent form.

The doctor will insert a plastic needle, (cannula) into a vein in your arm and the medicine for sedation is given through this.

You will be asked to remove glasses and dentures if you are wearing them. If you are wearing a hearing aid you may leave this in place.

You will be given oxygen through a face mask.

For the procedure you will lie on your left side with your knees slightly bent.

The endoscopist gently inserts the scope into your bottom and passes it through to your colon (large bowel). During the procedure, air is put into your colon to give a clear view of its lining. You may experience some wind-like pains but they will not last long.

The colonoscopy procedure usually takes 30 minutes but times can vary considerably.

After your colonoscopy

In the recovery room

The staff nurse will give you some more oxygen through a mask. They will measure and document your blood pressure, pulse and oxygen levels.

You will sleep off your sedation for anything up to 1 hour.

You will be helped from the trolley onto a chair to get dressed.

A nurse will remove the cannula, (plastic needle) from your arm.

You will be offered tea or coffee and toast.

A nurse will give you written post-procedure instructions. They will remove any identification bands.

A member of the medical team will speak with you before you go home and a copy of the report will be sent to your GP.

If you need a follow-up appointment, you will get a letter about this with the time and date.

You cannot leave the unit alone.

Going home

The medication will make you too drowsy to drive for 24 hours afterwards. You should arrange for someone to bring you home from hospital. If not, we may have to cancel your test.

After the colonoscopy we will tell you if we took any samples or if we removed any polyps. You will get the results in 2 weeks.

If the colonoscopy shows that you need more tests or treatment we will discuss and explain this to you and together decide the best course of action.

It can happen that the doctor may not be able to see all of your bowel. This can happen if your bowel was not completely empty or the tube could not reach the end of your bowel. We may ask you to have another colonoscopy or another test. We will send a copy of your results to your GP.

Content supplied by the National Screening Service
Reviewed by: Professor Diarmuid O'Donoghue

page last reviewed: 18/06/2019
next review due: 18/06/2022