Computed tomography colonoscopy: interpretation and pitfalls

Virtual colonoscopy by computed tomography (CT) is a non-invasive imaging technique that allows generating two-dimensional reconstructions and endoluminal navigation images of the colon. Four factors determine the success of the study: colonic preparation, distension, quality of the images obtained, and their interpretation. Preparation is essential, for which an intestinal cleansing and oral contrast is required to be able to stain traces of residual fecal matter. Colon distension is performed by introducing a rectal cannula through which carbon dioxide is insufflated. Although the process may represent some discomfort for the patient, emphasis must be placed on explaining to the patient that correct distension is a fundamental point of the study. Careful analysis of two-dimensional images and endoluminal navigation images is important to avoid diagnostic errors. Artifacts and pseudolesions are more frequent findings than true colonic pathology. It is important for the radiologist to be aware of them to avoid misinterpretation and unnecessary procedures for the patient. Possible errors in the interpretation of this method are technical sources of error, anatomical pitfalls and pseudolesions. The aim of this article is to identify artifacts and pseudolesions of CT colonoscopy, providing strategies to recognise and prevent them.