CT Colonography
With bowel cancer being the third most common cancer in the world, and New Zealand and Australia having the world’s highest rates of diagnosis, TRG Group continues to focus on CT Colonography (or ‘Virtual Colonoscopy’) as a key tool in the fight against the disease.
This examination is widely regarded as more comfortable than conventional colonoscopy and uses our low dose multislice CT scanners to scan the entire abdomen and pelvis. Our workstation then post-processes this data and delivers useful and interactive images.This includes 3D images where the bowel is literally "flown-through".
Colorectal cancer is predominantly a preventable disease if precursor adenomatous polyps are identified at an early stage and subsequently removed. Hence the relatively non-invasive CT Colonography examination has become highly valued byMedical Specialists, General Practitioners and their patients.
Colonic Polyps and Colon Cancer
The prevalence of colonic polyps increases with age, particularly beyond 50 years. Untreated, many colonic polyps progress to carcinoma over several years. The risk of cancer developingin sporadic 10 mm colonic polyps is approximately 8% at 10 years and 24% at 20 years. The risk forcancer development depends on the size of the polyp,villous histology, and its association with polyposis syndromes.
CT Colonography (CTC) is especially useful:
- In elderly and frail patients
- When colonoscopy may be higher risk e.g.
patients on anticoagulants - Following failed or incomplete colonoscopy:
If the incomplete colonoscopy is an obstructing lesion then a combined CTC and staging CT scan (using IV contrast) may be performed - When colonoscopy may be difficult or painful: eg: following diverticulitis (wait 6 weeks before CTC)
What’s involved?
- BowelcleansingLowresiduediet 2 days before.
- Cleansinglaxativesthe day before.
- FaecaltaggingOral stool marking. Makes residual bowel contents relatively dense
- ProcedureSmall flexible tube inserted in rectum. Bowel inflated with air or CO2.
- CT Scan Usually quick recovery after examination.
- No IV contrast or sedation. Supine and prone series to distribute the fluid and gas.
- Examinationtime - approximately 45 minutes
- Welltolerated- drive home after the examination.
Comparison of CT Colonography (CTC) to Colonoscopy
- Accuracy – both techniques have an accuracy of >95% for the detection of polyps > 10mm.
- Colonoscopy is better for detection of flat lesions and smaller polyps
- CTC is better for extra-colonic lesions (8% require additional workup and 2% are significant)
CT Colonography (CTC) is indicated for:
- Diagnosis/exclusion of colorectal cancer in symptomatic patients: especially with symptoms with a relatively low risk of colonic malignancy eg change of bowel habit, abdominal pain, weight loss, (patients who may have had a barium enema in the past).
- For screening in asymptomatic average risk people.
When CTC is not the test of choice:
- Suspected mucosal lesions such as inflammatory bowel disease and angiodysplasia.
- Known polyp syndromes (including familial) where biopsy is likely
- Young patients (<40 years) as there is a greater potential radiation risk
- Males with Fe deficiency anaemia (20% positive predictive value for significant lesion)
- Positive iFOBT. Expected to have a significant finding in up to 40%.
Why trg group ?
We have caring staff who look after your patient during and after the procedure. All our CT scanners have additional software to give a 30% radiation dose reduction compared with standard CT scanners. Our specialist radiologists are well qualified to interpret the scans.