Advice for optimizing colonic distention and minimizing risk of perforation during CT colonography.

Abraham H. Dachman, MD Computed tomographic (CT) colonography is an attractive alternate to optical colonoscopy in some patients because of its less invasive nature and the fact that sedation is not required. In this issue of Radiology, two articles report the findings of retrospective studies on the incidence of colonic perforation during CT colonography (1,2). These reports emphasize the fact that although CT colonography is less invasive and has fewer complications than optical colonoscopy, it is not free of potential risks. To my knowledge, the actual complication rate for CT colonography has not been well studied prospectively; this is mostly because no complications were initially reported and partly because no single clinical trial can be large enough to include rare complications and some colonic perforations are asymptomatic and might be visible only after conclusion of the examination. Complications include (a) prolonged cramping related to gaseous distention of the colon; (b) nausea, vomiting, or vasovagal reactions that can be caused by either colonic distention or administration of a spasmolytic (glucagon in the United States and hyoscine butyl bromide in Canada and Europe); and, rarely, (c) colonic perforations (1–4). Successful colonic distention with CT colonography is multifactorial and requires knowledge and experience on the part of the technologist or radiologist monitoring the insufflation. The desire to maximize patient comfort and minimize the risk of perforation might lead to a conservative approach during colonic insufflation and result in somewhat suboptimal colonic distention. This approach might decrease reader confidence in the interpretation and lead to decreased sensitivity for detection of polyps or decreased specificity because of false-positive findings in suboptimally distended segments. Since optimal colonic distention is a critical requirement for obtaining an optimal study, these recent reports could adversely affect the diagnostic performance of CT colonography. The data on colonic distention in prior CT colonography reports can be a source of confusion because changing one variable can dramatically change the findings. One cannot mix and match recommendations regarding (a) the use of glucagon, air versus carbon dioxide, and mechanical insufflation versus manual insufflation versus self-insufflation; (b) the rate or volume of inflation; and (c) the end point for obtaining CT images. Each variable must be evaluated separately to understand its effect on distention and patient comfort. The purpose of this editorial is to describe strategies for optimizing colonic distention and patient comfort while minimizing the risk of perforation.