A colonoscopy is a diagnostic procedure which involves inserting a thin flexible tube into the bowel via the anus. The tube is equipped with a video camera and light, allowing the surgeon to view the bowel wall and detect any abnormal tissue. Most commonly this abnormal tissue (if present) is in the form of one or more 'polyps' - a protrusion of tissue from the bowel wall. Polyps can be large or small (anywhere from 2mm-60mm in diameter).
Although relatively common, not all polyps are cancerous or pre-cancerous - the majority are benign - however, it is standard practice to remove polyps during a colostomy and send these tissue samples to be tested. This is done as it is not possible to detect whether a polyp is cancerous simply by visualising it. Polyps generally have no obvious symptoms. although larger ones can cause some bleeding and are more likely to contain abnormal cells (ie cancer cells).
The process of removing a polyp is called 'polypectomy'. It is performed by passing a loop of wire around the polyp, and tightening this while sending electric current through the wire.
A colonoscopy is generally recommended where:
- There is a family history of bowel cancer.
- The person has already been diagnosed with bowel cancer or another bowel condition (e.g. inflammatory bowel disease).
- The person has had one or more polyps removed during a previous colonoscopy.
- There has been a continuing change in bowel habit.
- There has been any bleeding from the rectum / anus.
- A Faecal Occult Blood Test (FOBT) has come back positive.
How should I prepare for the procedure?
The most important thing is that the bowel is completely clean and empty for the colonoscopy, so the surgeon can properly view the bowel wall. This is achieved by taking a special fluid preparation (called Picoprep) beforehand which empty the bowel and restricting food intake prior to the procedure.
Here are the steps you need to take to prepare for the procedure, starting seven days beforehand:
7 Days Before Procedure
If taking iron tablets, stop taking these now.
1 Day Before Procedure
Breakfast the day before should be the last solid meal before the procedure. After this meal, only clear liquids such as:
- Clear soup.
- Black coffee.
- Black tea.
- Fruit juice (no pulp).
No red/purple drinks. Jelly can also be eaten (but no red/purple coloured jelly).
From 12am Midnight until the Procedure
You should not eat or drink anything, ie observe 'nil by mouth'.
Picoprep Solution - Guidelines
Picoprep solution - there should be three sachets in the kit. These should be taken with 250ml warm water (stir powder in until completely dissolved) at the following times...
- 12:00 pm midday – Sachet 1.
- 3:00 pm – Sachet 2.
- 6:00 pm – Sachet 3.
These glasses should be drunk slowly over 5-10 minutes and then followed by 3 or 4 glasses of one of the fluids listed above in the following 30-40 minutes.
Once this process is underway, you will feel the need to go to the toilet and this will start the process of cleansing your bowel. The bowel motions will become very watery - this is perfectly normal. If you feel any soreness around the anus as a result, you can use a cream (such as lanolin) to ease this.
What is involved in a colonoscopy?
A colonoscopy is generally conducted under a light anaesthetic and takes 20-60 minutes to complete. You lie on your side, with your knees pulled up towards your chest.
After the colonoscopy is complete, you will be kept under observation for a short time and then allowed to return home. You should return home to rest (do not return to work) and you should not drive yourself, as you will still be affected by the anaesthetic for the rest of the day.
Alternatives to colonoscopy
There is an alternative to a standard colonoscopy – this is a CT scan performed when the bowel is empty and slightly inflated with a small quantity of air introduced via the anus. This is often referred to as a 'virtual colonoscopy'. The disadvantage of this approach is that if any abnormal tissue or polyps are found, they will need to be re-examined and if necessary removed during a standard colonoscopy.
A colonoscopy rarely causes complications. The following are rare, but can occur:
- Reaction to anaesthetic.
- Bleeding from biopsy / polypectomy site.
- Perforation of rectum/colon wall.
When to contact Dr White
If you experience any of the following you should contact Dr White immediately (or your doctor / GP or out of hours go to your local emergency department):
- Difficulty urinating.
- Bleeding (in excess of that described above).
- High temperature / fever.
- Pain that is severe or getting worse.