A colonoscopy is the most accurate test for examining the large bowel. Doctors advise it when symptoms need to be explained, and it often allows treatment in the same sitting. This article covers the reasons you may need a colonoscopy, how to prepare, what happens on the day and what the results mean.
What is a colonoscopy?
A colonoscope is a thin, flexible tube with a light and camera at its tip. It is passed gently through the back passage so the doctor can see the lining of the rectum and the whole colon on a screen. Small instruments can be passed through it to take samples or remove polyps. Read more about colonoscopy and endoscopic care.
Symptoms that may need a colonoscopy
- Blood in the stool or bleeding from the back passage
- A change in bowel habit lasting more than a few weeks
- Long-lasting diarrhoea or constipation without a clear cause
- Unexplained iron-deficiency anaemia
- Unexplained weight loss or ongoing abdominal pain
- An abnormal finding on a scan or stool test
Other reasons your doctor may advise it
- A family history of bowel cancer or polyps
- Follow-up after polyps were removed
- Check-ups after treatment for bowel cancer
- Monitoring of inflammatory bowel disease
How to prepare
- Diet. You will be asked to eat a light, low-fibre diet and then take only clear fluids before the test.
- Bowel cleansing. You will drink a laxative solution that empties the bowel. Expect frequent loose motions; stay near a toilet.
- Medicines. Tell your doctor about blood thinners, iron tablets and diabetes medicines. Do not stop any medicine unless you are told to.
- Company. Arrange for an adult to accompany you home.
Good preparation is the most important thing you can do. If the bowel is not clean, small polyps can be missed and the test may have to be repeated.
What happens on the day
You will be asked to lie on your side. Sedation is usually given through a vein so that you are relaxed and comfortable. The doctor passes the colonoscope around the bowel and examines the lining carefully as it is withdrawn. The test usually takes less than an hour, and you rest afterwards until the sedation wears off.
After the test
Mild bloating or wind is common for a few hours. You can usually eat normally the same day. Do not drive, operate machinery or sign important documents until the next day if you had sedation. A small amount of blood in the first motion can occur after a biopsy or polyp removal.
Seek medical help if you have severe abdominal pain, heavy or continuing bleeding, or fever after the test.
Understanding the results
The doctor will usually tell you what was seen before you go home. Results of biopsies and removed polyps come from the laboratory some days later. Depending on the findings you may need no further action, a repeat colonoscopy after some years, or treatment.
Frequently asked questions
Is there an alternative to colonoscopy?
Stool tests and scans can give useful information, but they cannot take samples or remove polyps. If they show an abnormality, a colonoscopy is usually still needed.
How long does the whole visit take?
Plan for a few hours, including preparation, the test and recovery from sedation.
Can I have it during my period or if I have piles?
Yes. Neither prevents the test from being done.
If you have any of the symptoms above, request an appointment to discuss whether a colonoscopy is right for you.
This article is for general awareness and does not replace a consultation with a doctor.