Colonoscopy factsheet


A colonoscopy is a procedure that is done to look inside the bottom half of the digestive system.

The bottom half of the digestive system is the large intestine, also known as the bowel. It includes the:

  • colon – the largest part of the long intestine, where the last parts of water and nutrients are absorbed out of digested food and the waste is turned into faeces or poo
  • rectum – the last part of the large intestine, where poo is held until it is passed out of the body.

In a colonoscopy, a long flexible tube with a camera lens and light is inserted into the rectum and up into the colon to let the doctor see inside. This tube is called a colonoscope.

A colonoscopy is usually done to find out why your child has:

  • abdominal or belly pain
  • diarrhoea or loose poo
  • blood in their poo.
  • anaemia – a lower than normal level of red blood cells

The colonoscopy looks for:

  • inflammation
  • redness
  • bleeding
  • ulcers – sores that develop on the inside of the body
  • polyps – small growths that form on the inside of the body.

Sometimes a colonoscopy is done at the same time as an upper endoscopy. An upper endoscopy is a procedure that looks at the top half of the digestive system.

 Before the procedure

You will be contacted by the hospital and given information about: 

  • anaesthetic and fasting instructions
  • bowel preparation
  • what time to arrive.

The colonoscopy is done while your child is under a general anaesthetic. This means they will be asleep and not feel any discomfort. 

Bowel preparation

Before a colonoscopy, your child must empty their bowel using a strong laxative called bowel preparation. This is to make sure the camera can take clear pictures of the bowel.

Your child’s treatment team will give you:

  • the bowel preparation mixture
  • instructions on how to prepare and drink the mixture
  • information about foods to avoid.

Speak to your child’s treatment team if they are struggling to drink the mixture. 

Passing clear liquid is a sign that the bowel is empty.

 During the procedure

The procedure will take between 30-60 minutes. This will depend on whether:

  • the doctor finds anything in the bowel
  • there is another procedure happening at the same time.

Generally, the steps of a colonoscopy procedure are:

  1. the colonoscope is passed through the rectum and gently pushed up into the colon until it reaches the end of the small bowel
  2. carbon dioxide gas and sterile water are gently pumped through the colonoscope into the colon to inflate it, giving a better view of the lining
  3. pictures are taken of the lining
  4. a small sample of the lining is taken out for testing, also called a biopsy.


In some cases, the doctor might find polyps inside the bowel. 

Polyps are small growths that are usually harmless but can develop into cancer. Polyps can be removed during the colonoscopy by inserting a small instrument through the colonoscope and snipping the polyp off. 

If the polyps are large, the doctor may use a clip or noose to tie the bottom of the growth before removing it. 

The removed polyp will be sent off for testing to make sure there is no cancer present.

 After the test

After the procedure, the doctor will let you know if anything was found, and the next steps. Results from the biopsy and polyps may take longer, so a follow-up appointment will be made. 

Your child may be groggy and nauseous after the procedure. They may also have some:

  • minor bleeding
  • gas and bloating
  • general discomfort.

Your child should start to feel better after some time in recovery and will usually be able to go home the same day.


Tips for bowel preparation

Bowel preparation is a strong laxative that works to empty the bowel. It can be difficult for children to drink all the liquid and manage to go to the toilet more than usual to empty their bowels.

Try some of these tips to make bowel preparation more comfortable:

  • ask your child’s doctor about clear liquids they can have, and let your child choose the drink or ice block they want to have
  • buy some toilet paper for your child that is especially thick and soft
  • try alternating wiping with showers, a bidet, or a peri-bottle if your child’s bottom is becoming sore and irritated
  • buy some wipes for your child to use - make sure they are not flushed down the toilet even if they are marketed as “flushable”
  • ask your child’s doctor about creams or ointment for irritation around the anus
  • make sure your child is at home and close to a toilet during the bowel preparation as they may have difficulty getting to the toilet in time
  • get some activities your child can do on the toilet, like colouring in books, videogames, or music
  • have extra towels and spare clothes on hand just in case your child does not make it to the toilet in time.

Make sure to give your child lots of encouragement while acknowledging that bowel preparation is unpleasant.

Complications and risks

Like any procedure, there are complications and risks with a colonoscopy. 

These can include:

  • aspiration - inhaling food or fluid into the lungs while under anaesthetic 
  • reaction to medication used for the general anaesthetic
  • bleeding from the biopsy and removal of polyps
  • infection.

Your child’s doctor will talk to you about risks and complications before the procedure. Make sure you ask any questions you might have.

When to speak to your doctor

Go to your nearest emergency department as soon as possible if your child shows the following signs after the colonoscopy:

  • severe abdominal pain, worse than cramps from gas
  • a firm, enlarged belly
  • vomiting that is yellow to green in colour
  • fever
  • large amount of bleeding from the rectum.
Last updated Tuesday 16th April 2024


This factsheet is provided for general information only. It does not constitute health advice and should not be used to diagnose or treat any health condition.

Please consult with your doctor or other health professional to make sure this information is right for you and/or your child.

The Sydney Children’s Hospitals Network does not accept responsibility for inaccuracies or omissions, the interpretation of the information, or for success or appropriateness of any treatment described in the factsheet.

© Sydney Children’s Hospitals Network 2024