Learning About Bowel Health
Dr Louise Moore, diagnostic radiologist at Bay Radiology, Tauranga.
WHY DO I NEED TO CHECK ON MY BOWEL HEALTH?
Colon cancer (also known as colorectal or bowel cancer) is a leading cause of cancer deaths in New Zealand. Bowel cancer most commonly starts within polyps. Polyps are growths arising from the surface of the colon or rectum. They become very common as people get older. Although polyps are non-cancerous (benign), occasionally a change can take place inside a polyp and bowel cancer can start. Colon cancer is often silent for many years. If caught early, colon cancer may be cured.
WHAT IS A CT COLONOGRAPHY?
CT colonography (CTC), is a CT scan to look at the colon, or large bowel. A CT scan is a specialised x-ray test, during which the patient lies on a moving table/bed as it passes through a circular x-ray machine.
WHY WOULD MY DOCTOR REFER ME TO HAVE THIS PROCEDURE?
The main purpose of a CTC is to look for cancer or polyps in the large bowel. If a cancer or significant sized polyp is found, you will need to have another test, such as a colonoscopy for biopsy or to remove the polyp. CTC is also excellent for diagnosing diverticulitis, where pouches develop in the wall of the colon, or as an investigation if you have symptoms suggestive of bowel problems. Another reason to have a CTC is if you have had a difficult or incomplete conventional colonoscopy, when the whole bowel may not have been completely or confidently assessed.
WHAT DOES THE CT COLONOGRAPHY EXAMINATION INVOLVE?
In order to study the large bowel, dietary preparation and prescribed laxatives are required to cleanse the bowel. During the examination, the large bowel is filled with carbon dioxide through a small tube in the rectum and then a CTC scan is performed. A bowel relaxant is usually given to help this process. The carbon dioxide is readily absorbed by the body, which reduces the discomfort experienced. No sedation is required and it is generally possible to return to work shortly after the procedure. After the CTC scan, a radiologist with expertise in interpreting CTC will analyse the images and give a written report to your referring doctor.
ARE THERE ALTERNATIVE TESTS TO CT COLONOGRAPHY?
A colonoscopy is a standard way of examining the bowel, in which a tube with a camera on the end (colonoscope) is passed into the large bowel through the rectum. It is more invasive than CTC and usually requires sedation. Optical colonoscopy is the preferred screening test for people at higher risk of colon cancer. Discuss with your doctor which test may be right for you.
CT colonography is available through Bay Radiology, following a referral from your general practitioner or specialist.
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