The use and technique of CT colonography in identifying colonic lesions
CT colonography (CTC) is a valuable diagnostic tool for detecting colorectal cancer (CRC), particularly when traditional colonoscopy is contraindicated or incomplete. This article outlines the clinical application and technical execution of CTC, emphasising its role in bowel cancer screening and symptomatic patient evaluation. The accuracy of CTC is highly dependent on proper bowel preparation, which includes dietary restriction, cleansing and faecal tagging using iodinated contrast agents like Gastrografin.
To optimise imaging, spasmolytics such as Buscopan are used to reduce bowel motion, and automated CO2 insufflation ensures adequate colon distension. A rectal balloon helps retain gas but may obscure rectal lesions, necessitating deflation for at least one view. Scanning in multiple positions – typically supine and prone – is essential to redistribute gas and improve visualisation, with a third view added if needed.
The article discusses imaging limitations, such as poor preparation and distension, which can mimic pathology. It highlights the importance of radiographer expertise in identifying these issues and adjusting technique accordingly. Lesions are classified using the Paris system, distinguishing between polypoid and nonpolypoid morphologies, with flat and depressed lesions carrying higher malignancy risk.
CTC also enables extracolonic evaluation and staging through optional intravenous contrast and same-day thoracic imaging. The article underscores the need for trained radiographers and radiologists, supported by institutions like the National CT Colonography Academy, to ensure high quality examinations and reporting. Overall, CTC is presented as a sensitive, adaptable and patient-friendly alternative to colonoscopy in colorectal lesion detection.
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