II. Epidemiology
- Adjusted protocol has recently improved efficacy
- Same Bowel Preparation as Colonoscopy
- CT programmed to remove artifact
- Barium solution (500 cc) tags solid stool
- Opacifying solution (120 ml) tags fluid
- Adjusted protocol efficacy equivalent to Colonoscopy
- Polyps >6 mm
- Test Sensitivity: 88.7%
- Test Specificity: 79.6%
- Polyps >10 mm
- Test Sensitivity: 93.8%
- Test specificty: 96%
- Study showed lower predictive value of CTC
- Positive Predictive Value if >6 mm: 46.6%
- Positive Predictive Value if >6 mm: 50%
- Cotton (2004) JAMA 291:1713-9 [PubMed]
- Polyps >6 mm
- Proposed Indication
- Pre-screening for colonscopy in average risk patients
- Positive screening would result in Colonoscopy
- Colonoscopy would only be needed in a third of cases
- Causes of False Positives
- Residual stool
- Causes of False Negatives
- Flat lesions
- Polyps smaller than 10 mm
- Inadequate insufflation
- References
III. Advantages: Compared over Colonoscopy
- Well tolerated
- Minimally invasive without risk of bowel perforation
- No sedation required
- Fast procedure that images entire colon
IV. Disadvantages: Compared with Colonoscopy
- May not be covered by insurance
- Incidental findings in up to 70% of cases (but only 3% require management)
- Guidelines for significant polyp size not established
- Lesion biopsy requires another procedure (yet still requires all the Bowel Preparation)
- Radiation Exposure (equal to 70 plain Chest XRay films)
- Recommended every 5 years (instead of 10 years for Colonoscopy)