Chorionic Villous Sampling
What are the generally accepted indications for chorionic villous sampling? Chorionic villous sampling (CVS) is usually carried out between 11…Read more
Note: Individuals at higher risk of colon cancer because of positive faecal occult blood test, prior colonic neoplasia, family history or those with symptoms or signs requiring exclusion of carcinoma of the colon are better evaluated with optical colonoscopy, particularly because it is likely they will require biopsy/polypectomy. Additionally, patients with known inflammatory bowel disease or a high risk genetic condition, such as hereditary nonpolyposis colorectal cancer (Lynch syndrome), require assessment by a gastroenterologist, as it may be more appropriate to carry out conventional colonoscopy because of the high likelihood that biopsy will be required.
Note: CTC is not a preferred test in younger people, particularly less than 40 years of age, because of the radiation used in the procedure.
No specific laboratory tests or previous imaging tests are required.
Immediate: Abdominal discomfort, cramping, usually passes quickly. If Buscopan bowel muscle relaxant has been given, there may be the usual side-effects from this, such as transient visual blurring or, rarely, precipitation of glaucoma.
Delayed: Radiation-related cancer induction risk. This is not usually a valid consideration, as the benefit of the test in both screening and symptomatic groups is shown to outweigh this risk. For example, a standard CTC at age 50 years has been calculated to impart a 0.06% lifetime risk of radiation-related cancer; compared with an approximately 30% background chance of cancer – which includes the risk of a colorectal cancer that the CTC is intended to detect and prevent2.
There is no specific post procedural care following a CT colonography
Other tests to examine the colon are barium enema, and optical (conventional) colonoscopy, flexible sigmoidoscopy and varieties of faecal occult blood tests.
Population-based screening for adenomatous polyps and bowel cancer is a complex and evolving area. Decisions for screening need to take into account cost, diagnostic accuracy and safety.
Compared with optical colonoscopy, there are some advantages and disadvantages to CTC. These include:
Barium enema is relatively cheap and available, but has much lower accuracy for polyps and cancer, especially when small, compared with optical colonoscopy and CTC. This is no longer regarded as a first-line investigation for suspected bowel cancer in high- or low-risk populations. A contrast enema is useful in delineating the level and cause of an acute large bowel obstruction, especially when colonoscopy is difficult as a result of complete obstruction; for example, sigmoid volvulus or obstructing cancer.
Page last modified on 18/8/2017.
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RANZCR® intends by this statement to exclude liability for any such opinions, advices or information. The content of this publication is not intended as a substitute for medical advice. It is designed to support, not replace, the relationship that exists between a patient and his/her doctor. Some of the tests and procedures included in this publication may not be available at all radiology providers.
RANZCR® recommends that any specific questions regarding any procedure be discussed with a person's family doctor or medical specialist. Whilst every effort is made to ensure the accuracy of the information contained in this publication, RANZCR®, its Board, officers and employees assume no responsibility for its content, use, or interpretation. Each person should rely on their own inquires before making decisions that touch their own interests.