What is a Colonoscopy?

Colonoscopy is a procedure used to examine the large bowel. It allows a variety of functions to be carried out through the instrument. Such functions may include taking tissue samples (biopsies), the removal of polyps, dilation of narrowings, and various treatments to arrest certain forms of bowel haemorrhage.

How are you prepared?

Prior to your colonoscopy, you will be provided with a preparation kit containing full instructions. For three (3) days before the procedure, you will need to follow a low residue diet. The night before your colonoscopy, you will need to take laxatives and further preparation of a quantity of salty-tasting solution which completely flushes out the colon.

What do we do?

You will be given a sedative before your procedure begins and usually you will not remember the actual examination.

The colonoscope is a long and highly flexible tube about the thickness of the index finger. It is inserted through the rectum into the large bowel and allows inspection of the whole of the large bowel. Occasionally, narrowings of the bowel or other diseases may prevent the instrument being inserted through the full length of the colon.

As cancer of the large bowel can arise in pre-existing polyps, it is advisable that if polyps are found at the time of examination they should be removed. Most polyps can be removed by placing a wire snare (loop) around the base and, if necessary, applying an electric current.

How accurate is a Colonoscopy?

Few investigations in medicine are perfect. Colonoscopy has been shown to be significantly more accurate than barium enema in detection of bowel polyps and cancers. A number of recent studies have examined the accuracy of colonoscopy and concluded that where the instrument cannot be passed all the way around the colon, there is significant risk of missing polyps and cancers in the unexamined portion of the bowel. For this reason, if your colonoscopist is unable to pass the instrument the entire length of the colon, other procedures may be recommended.

With a complete colonoscopy, up to three per cent of bowel cancers can be missed. This risk appears to be smaller for highly-trained colonoscopists. Small benign polyps can be missed in up to six per cent of cases. The detection of small polyps is seriously hindered by poor bowel preparation.

Special Considerations

You must advise the nursing staff if you are allergic or sensitive to any drug or other substance.
If you have had a recent joint replacement, coronary stents or pacemaker insertion, antibiotic cover may be required.
You should cease iron tablets and drugs to stop diarrhoea at least seven (7) days before the procedure.

There are some medical conditions for which it is essential that your colonoscopist be told about:

  • Insulin-dependent diabetes
  • Heart valve disease – may require antibiotic cover.
  • Blood thinning medication:
    • Aspirin poses some increased risk. If you are taking aspirin as a lifestyle measure, then it should be ceased a week before your procedure. If you are taking it for a medical condition which is being treated by a doctor, then you should continue your aspirin.
    • Anti-coagulants (e.g. warfarin - such as Marevan or Coumadin; Pradaxa; Clexane; Dindevan; Xarelto; Eliquis) and anti-thrombotic agents (e.g. aspirin; Aggrastat; Arixtra; Asasantin; Persantin; clopidogrel - brands such as Iscover or Plavix; Effient; Brilinta; Reopro; Thrombotrol; Ticklid; Tilodene). Removal of polyps while on blood-thinning agents may result in serious haemorrhage. This is a complex problem where the risk of ceasing blood-thinning medication must be balanced against the risks of post-polypectomy haemorrhage. Depending on your medical background, these may or may not be stopped before your procedure and should be discussed with the doctor prior.

Removal of Polyps

The majority of bowel cancers arise from benign adenomatous polyps. Some polyps never become cancerous. It is impossible to predict which polyps will progress to cancers and which will remain as benign polyps. For this reason it is advised that all polyps be removed at the time of colonoscopy. However, it will not be possible to discuss this at the time (during the colonoscopy itself) as you will be sedated. If you have any queries or reservations about removing polyps, please inform the staff before the procedure. In the unlikely event that a haemorrhage occurs after removing a polyp, a blood transfusion or operation may be necessary and your will be transferred to a hospital for this treatment.

If large polyps are removed, a small metal clip may be placed around the base of the polyp stalk to reduce the risk of bleeding. Clips will be passed in the bowel motion usually within two weeks.

If a polyp is detected with some worrying features, then black ink is used to tattoo a mark adjacent to the polyp site. This permanently marks the site so it can always be checked again in the future, or if the area of bowel does require surgery, then the surgeon will immediately identify the site where the polyp was removed.

After your colonoscopy

The sedation/analgesia you are given before the procedure is very effective in reducing any discomfort. However, it may also affect your memory for some time afterwards. Even when the sedation appears to have worn off, you may find you are unable to recall details of your discussion with your doctor.

For a straightforward diagnostic procedure, you can return to normal food intake as soon as your sedation has worn off. You should, however, be careful to avoid alcohol over the next 12 hours as traces of sedation remaining in your blood steam may combine with alcohol to produce a far more intoxicating effect than normal.

During the procedure, it is necessary to fill the colon with air to ensure that all areas of the bowel are examined. Not all of this air can be removed at the end of the procedure and you are likely to feel some bloating and discomfort for a few hours afterwards.

If you have any severe abdominal pain, rectal bleeding, fever or other symptoms which cause you serious concern, then you should contact your doctor immediately.

Safety and risks

This is important information about potential complications. It is not our intention to frighten or dissuade you from having the investigation, but we must outline the risks. With this knowledge, you may either elect to accept the risks and proceed with the procedure, or decide not to have it. Depending on the reason for the procedure, there may be risks of NOT having the procedure (e.g. missed disease or delayed diagnosis). These risks may be fatal (e.g. delayed diagnosis of cancer).

For inspection of the bowel alone (diagnostic colonoscopy without removal of polyps or other operative measures), complications of colonoscopy are uncommon. Many surveys report complications in less than 1 in 1000 examinations. These complications will include intolerance of the bowel preparation and reaction to the sedatives used. Major complications such as perforation of the bowel, bowel haemorrhage, injury to the spleen or other internal organs are very uncommon but if they do occur, surgery may be required.

When procedures such as removal of polyps are carried out, there is a slightly higher risk of perforation or bleeding from the site where the polyp has been removed. Complications of sedation are uncommon and are usually avoided by administering oxygen, monitoring the blood oxygen levels by a finger probe, or monitoring by electrocardiograph (ECG). Rarely, however, particularly in patients with severe cardiac or lung disease, serious sedation reactions can occur.

A number of rare side-effects can occur with any medical procedure. Full details and rare complications can be discussed with your referring doctor before the procedure, or at the time of consultation with the Gastroenterologist.