Overview of computed tomographic colonography
- Stephan Anderson, MD
Stephan Anderson, MD
- Professor of Radiology
- Boston University School of Medicine
- Section Editors
- Kenneth K Tanabe, MD
Kenneth K Tanabe, MD
- Section Editor — Gastrointestinal Malignancies
- Professor of Surgery
- Harvard Medical School
- Jonathan B Kruskal, MD, PhD
Jonathan B Kruskal, MD, PhD
- Section Editor — Kidney Disease
- Professor of Radiology
- Harvard Medical School
Computed tomographic (CT) colonography (also virtual colonoscopy or CT colography) provides a computer-simulated endoluminal perspective of the air-filled distended colon . The technique uses conventional spiral or helical CT scan images acquired as an uninterrupted volume of data and employs sophisticated post-processing software to generate images that allow the operator to evaluate a cleansed colon in any chosen direction.
This topic will review the preparation, technique, and risks of CT colonography. The effectiveness of CT colonography in screening and the diagnosis of colorectal cancer are discussed in detail, separately. (See "Clinical presentation, diagnosis, and staging of colorectal cancer", section on 'CT colonography' and "Tests for screening for colorectal cancer: Stool tests, radiologic imaging and endoscopy", section on 'Computed tomography colonography'.)
Indications — Potential indications for CT colonography include the following:
●Screening for colorectal cancer (CRC) – CT colonography is an option for CRC screening in asymptomatic average-risk individuals over the age of 50 years [2,3]. However, the role of CT colonography in screening for CRC is controversial. While there is consensus that CT colonography should not be used for screening in patients at increased risk for CRC (eg, history of adenomas, inflammatory bowel disease, familial CRC syndrome), guidelines differ in their recommendations for CT colonography in average-risk individuals. Guidelines for CRC screening are discussed in detail, separately. (See "Screening for colorectal cancer: Strategies in patients at average risk", section on 'Guidelines for average-risk screening'.)
●Evaluation for synchronous CRC – In patients with a CRC in whom a complete colonoscopy cannot be performed due to the inability to pass the colonoscope beyond an obstructing tumor, a CT colography can rule out a proximal synchronous CRC. (See "Screening for colorectal cancer: Strategies in patients at average risk", section on 'Guidelines for average-risk screening'.)
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- Chang KJ, Caovan DB, Grand DJ, et al. Reducing radiation dose at CT colonography: decreasing tube voltage to 100 kVp. Radiology 2013; 266:791.
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- PATIENT SELECTION
- PATIENT PREPARATION
- Technique and data acquisition
- Image processing and reconstruction
- TEST PERFORMANCE
- Complications related to preparation
- Colonic perforation
- Radiation exposure
- Incidental extracolonic findings
- Other complications
- QUALITY INDICATORS
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS