What is a Computed Tomography (CT) Colonography?
Computed Tomography (CT) Colonography is an examination that uses x-ray to produce images of the internal structure of the large bowel. The images are then reported by a radiologist.
Is a Computed Tomography (CT) Colonography safe?
Yes. CT Colonography is minimally invasive, and does not carry the low but real (1 in 1500) risk of perforation associated with Conventional Colonoscopy. It is well tolerated and does not require sedation.
Why should I have this examiantion?
In Malaysia, colorectal cancer is the third most common cancer with the incidence of 27 cases per 100,000 population (data from Natianal Cancer Registry Malaysia 2003). CTC is a promising new method for detecting colorectal polyps and cancers. In addition, most patients report that the CT Colonography technique is more comfortable than either Barium Enema or Conventional Colonoscopy.
Who should have a CT Colonography?
It is recommended if you:
- are 50 years of age and older
- have had a history of bowel polyps
- have a family history of bowel polyps or colon cancer.
- have had a failed colonoscopy examination.
- have unexplained change in bowel habit, anemia, rectal bleeding
How is a CT Colonography done?
You will be given a gown to change in the changing room. You have to remove all your accessories and then you will be taken to a CT suite.
An intravenous injection to reduce bowel movements will be given. A small tube is inserted into your rectum. Following this, air is pumped gently into the anus to distend the bowel. You will be scanned in two position, supine (face up) and subsequently prone (face down). Breathold instructions are given and the scanning will begin. You will feel the couch moving into the gantry (a doughnut-shaped device) during the scan.
How can I prepare for the CT Colonography?
You will be put on a low residue diet for a day prior to the scan. You will also be given some laxatives to clear your bowel of stools. You need to fast for at least 6 hours before the scan. If you are a woman, you need to ensure that you are not pregnant to prevent inadvertent radiation to your foetus. Please also inform the doctor if you have glaucoma, bladder outlet obstruction or arrhythmia (irregular heart beats) prior to this scan.
How long does a CT Colonography take?
The CT machine scans from head to toe in just less than 10 seconds. However, the total time taken to prepare and position the patient for the scan, to and from the CT suite is about 30-40 minutes.
What happens after the CT Colonography?
Your tummy may feel bloated for a day or two. You may also not have your normal bowel movements during this time as your bowel may have emptied after taking the laxative.
Are there any possible complications?
Radiation is associated with a small but known risk of cancer from data gathered from atomic bomb survivors. To date, there is still no documented evidence of cancer arising as a result of a diagnostic scan such as a CT colonography. There is also a theoretical risk of bowel injury due to distension by air. The intravenous injection to reduce bowel movements may precipitate an attack of glaucoma, an episode of urinary retention and cardiac arrhythmia in susceptible individuals.
What does it mean if my scan is positive or equivocal?
If your scan is positive or equivocal, it means that you may have a growth. You will likely need to undergo a colonoscopy for biopsy or polyp removal to confirm the exact nature of the growth.
Does a negative scan mean that I am free from colon cancer?
Yes. However, technically it is possible to miss very small cancer. Even with Conventional Colonoscopy, there are no guarantee that all growths will be detected. Between 10 and 20 percent of all polyps, and up to 5 percent of colon cancers are missed on Conventional Colonoscopy.
Disclaimer: This is only general information. A doctor should be contacted if you need any medical advice or if medical decisions need to be made.