An Overview of the Method, Application, and Various Findings of Computed Tomographic Colonography in Patients After Incomplete Colonoscopy

Colon cancer is the third most common malignancy in the USA with 154,000 new cases and 52,000 deaths in 2007. The current screening method is optical colonoscopy; however, the compliance rate of the screening population is very low. Computed tomographic (CT) colonography has been used as an alternative to optical colonoscopy as a screening method. The purpose of this article is to explain how CT colonography has been used as a supplemental screening tool in a subset of patients in whom optical colonoscopy was either incomplete or not possible. We examined a group of 222 patients at our institution in which a complete colonoscopy could not be performed for a variety of reasons. Routine CT colonography imaging of the insufflated colon was performed in both the supine and the prone positions with oral contrast. 3D reconstructed images were then obtained using Viatronix software and were interpreted along with the axial images. Each patient was classified into groups based on the quality/adequacy of the examination, presence, number, and size of polyps. The patients were also evaluated for any diverticula, benign lesions such as lipoma, stricture, or mass. In addition to its use as a primary screening tool, CT colonography can be used as an adjunct to optical colonoscopy as in our institution. A cooperative use of both screening modalities can result in a higher number of completed examinations when combining the results of both tests. On review of our 222 cases, there were 37 patients in whom the CT colonography was deemed incomplete for several reasons, including inadequate insufflation, persistent stricture, or incomplete preparation. Of these cases, when reviewing the previous incomplete colonoscopy report, 18 patients (49%) had a complete screening study when combining the results of both tests. In these cases, areas that could not be evaluated by CT colonography were properly screened with colonoscopy. A large number of patients in our study group were able to receive an essentially complete screening evaluation when both tests were combined. In the case of our study, the combination of both tests brought the rate of complete studies to 91%.