How to Get the Colon Distended?

The importance of achieving optimal colonic disten-tion prior to CT colonography cannot be overstated, and the editors have justifiably devoted an entire chapter to the subject. Optimal luminal distention enables the reader to rapidly and confidently assess the colon, and undoubtedly improves diagnostic accuracy (Chen et al. 1999; Fletcher et al. 2000; Yee et al. 2003). Conversely, inadequate distention may obliterate the colonic lumen and result in wall/haustral fold thickening (Fig. 7.1), thereby variously hiding or mimicking colorectal neoplasia (Fig. 7.2a, b) (Fletcher et al. 1999; Macari Megibow 2001; Fenlon 2002). Interpretation times are increased when the colon is poorly distended, but of greater importance is the potential to miss significant colonic pathology (Fig. 7.3a–c), occasionally rendering the examination non-diagnostic (i.e. necessitating repeat examination or endoscopic referral) or sometimes frankly misleading. For example, a review of missed significant lesions from a large prospective multicenter trial of CT colonography (Rockey et al. 2005; Paulson et al. 2004) found that suboptimal distention, along with poor preparation, was implicated as a contributing factor in 16 of 28 (57%) false-negative examinations.