CT Colonography

What is CT Colonography?

A CT colonography (CTC) is an examination of the internal wall of the colon (the mucosal lining of the large bowel). The aim of a CTC examination is to detect polyps in the colon.  Polyps are growths that begin from the lining of the bowel.  Some bowel polyps have the potential to develop into bowel cancer, therefore early detection and if appropriate removal can significantly reduce the risk of developing bowel cancer.  Most bowel cancers develop from a bowel polyp.

A CTC will accurately identify any significant polyps that may require monitoring or removal by a specialist.  10% of the population (over 50 yrs of age) will have bowel polyps, of which a small percentage will require removal.  CTC is proven in clinical trials to be as accurate as colonoscopy at finding significant polyps and provides a viable, effective and safe alternative.  A CTC examination is both a reliable screening tool and will detect bowel cancer if present in the large bowel.

Who should have a CTC?

We suggest the following guidelines:

• Adults over the age of 50 (every five years thereafter).
• Adults with a  family history of bowel polyps.
• Adults (over the age of 40) with first degree relatives diagnosed with bowel cancer.
• Anyone who has had a change in bowel habits.

Who should not have a CTC?

• Adults with a recent (less than 6 weeks) acute diverticulitis or active inflammatory bowel disease.
• Adults with a history of ulcerative colitis or crohns disease, people with hereditary conditions such as familial adenomatous polyposis and hereditary non polyposis cancer syndromes.

Do I have to have any preparations for a CTC?

Yes it is very important to cleanse the colon prior to a CTC examination. This ensures the radiologist can clearly visualise any polyps that might be present. Bowel preparation (pills and fluid) are arranged for you to take the evening before the CTC appointment. You will also have a limited diet (clear fluids) the day prior and the morning of your examination. You can expect to need to use the toilet (to empty the bowels) about 1-3 times the evening prior to your appointment.

 

What are the advantages of a CTC?

• A CTC is minimally invasive and can detect polyps and lesions as clearly as when they are directly seen by colonoscopy.
• CTC has a markedly lower risk of bowel perforation than conventional colonoscopy.
• No sedation is required for a CTC and therefore no recovery period is required. People can return to normal activities and diet immediately after a CTC.
• The cost of a CTC is less than half that of a colonoscopy.
• A CTC is an excellent alternative for patients that have clinical factors that increase the risk of complications from colonoscopy, such as treatment with blood thinners or breathing difficulties. A CTC can also be an appropriate study for the elderly especially those who are ill or frail.
• Although a CTC is intended to examine the colon specifically, incidental findings or disease within the abdomen or pelvis may be visualised during this examination also.
• Most people will not have polyps and will require no other investigation.

What are the disadvantages of a CTC?

• A CTC examination uses xrays during the acquisition of images therefore there is a small radiation dose associated with this procedure.
• If a polyp of significance is found you may need a second procedure (colonoscopy) to remove this.

What happens during the examination?

Once you arrive for your appointment the radiographer will discuss the examination with you and answer any further questions you may have. You will change into a gown and be asked to use the toilet once more before the examination is started. You will then rest on the CT table on your side while a very small flexible tube is passed into your rectum (this allows Carbon Dioxide to be gently passed into your colon). Your privacy is respected at all times.

The vast majority of people who have CT colonography report a feeling of fullness, that they feel  they need to use the toilet to empty their bowels or have a gripey/gurgly sensation in their abdomen.  These sensations are completely normal and are a result of the C02 distending the colon (to eliminate any folds that might obscure polyps during the reporting process).  This sensation will pass very quickly and in our experience will take about three minutes to settle once the distention process has ended.

The table moves through the scanner as two sets of scans are acquired, the first with you resting on your back and the second resting on your front.  You will be asked to hold your breath for each scan (8-10 seconds each time).  The radiographers are very skilled with this examination and aim to minimise the time taken whilst obtaining the best possible visualisation of the colon. A CTC on average will take 15 minutes.

 

How does the CT scanner get such detailed images?

A CT scanner aquires multiple cross sectional images of the body, this data can be converted into detailed 3 dimensional images.  During  CT colonography a detailed three dimensional model of the abdomen and pelvis is produced.  The Radiologist can then view the internal wall/mucosal lining of the colon(the large bowel) in a way that simulates travelling along the colon (this is often called a virtual colonoscopy).

What happens afterwards?

 

Once the radiographer has removed the rectal tube you will return to the change cubicle and get dressed again. We encourage people to stay and have a warm drink and biscuit after the CTC, you will be able to return to normal activities immediately after your CTC.  If you feel a little tired (due to the previous nights toilet visits!) you may wish to factor in enough time to rest and arrange to have a late breakfast before embarking on the day.

 

Who interprets the results and how do I get them?

A radiologist with expertise in interpreting CTC examinations will analyse the images and send a report to your doctor, who will then discuss the results with you. We aim to have your CTC results with your doctor within 48 hours.

How do I arrange a CTC?
Firstly discuss with your Doctor if this is the appropriate examination for you, and if so, they will need to complete a referral form.  A routine blood test may also be required prior to embarking on the bowel cleansing preparation.  Once a CTC referral has been received by NRL a morning appointment will be made in liaison with you.

 

How much does a CTC cost?
The cost of a CTC is $788.50 (incl GST).

NRL has payment installment options for this particular examination.  You will need to ask to speak to the Accounts Manager to discuss this further.  Most insurance companies do not reimburse the cost of a CTC examination as a screening examination.  However should you present to your doctor with  a change in bowel habits or bowel symptoms  a CTC is recognised as an investigative procedure and is generally covered by most insurance companies. 

 

Further questions?
Please contact Nelson Radiology on (03) 548 2745.  Ask to speak to one of the CT radiographers involved in the CTC examinations for further information.