CT colonography: The Essentials

Pieter Vandaele, MD, M. Raquel Oliva, MD, Matthew A. Barish, MD, Koenraad J. Mortelé, MD


Appl Radiol. 2006;35(1) 

In This Article

Abstract and Introduction

Computed tomography colonography (CTC) is a promising method for detecting colorectal polyps and cancers. Although CTC is best suited for patients who are unable or unwilling to undergo conventional colonoscopy, its role as a colon cancer screening tool is somewhat controversial. This article presents important issues for radiologists who perform CT colonography or would like to do so. The authors address patient preparation and examination, technical scanning parameters and interpretation issues, the interpretation of colorectal mucosal lesions, the validity/performance and accepted clinical role of CTC, extracolonic findings, and the future applications of CTC.

Computed tomography (CT) colonography (virtual colonoscopy) is a promising new method for detecting colorectal polyps and cancers. Although multiple articles on this issue have been published since the mid-1990s, it remains an important discussion topic in current radiology and gastroenterology societies. Regarding its clinical role, there is no doubt that this imaging technique is best suited and highly recommended for those patients who are unable or unwilling to undergo conventional colonoscopy. Its role as a general screening tool for colon cancer is obvious for many, equivocal for some, and doubtful for others. This article is de-signed to highlight issues of importance for radiologists who are considering or who have recently started offering CT colonography to their patients and referring physicians.

Colorectal cancer is the second leading cause of cancer-related deaths in the United States.[1] The majority of colorectal cancers are believed to arise within benign adenomatous polyps and follow the adenoma-carcinoma sequence. The duration of this sequence is very long (±10 years),[2] and the removal of these precursor adenomatous polyps decreases the risk for lethal colorectal cancer significantly.[3]

CT colonography uses multidetector-row CT to generate data, which is then converted by computer software into 2-dimensional (2D) and 3-dimensional (3D) displays of the colon. CT colonography has several advantages over conventional colonoscopy: No sedation is needed, it is only minimally invasive, and the examination is less time-consuming than conventional colonoscopy. However, there is still a need for bowel cleansing and insufflation of gas to expand the colon. Moreover, exposure to radiation is inherent to CT, and there is no possibility of biopsy, polypectomy, or treatment during the examination.


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