Distension Suboptimal

Fig. 3.5. a Poor distension of the descending colon limits the diagnostic ability for lesions on this axial image, b Endolumi-nal view in the same patient showing suboptimal distension which inhibits navigation through this segment... 

Several strategies have been shown to improve distension, the most notable being dual patient positioning (i.e. prone and supine scanning). Use of faster multi-detector row scanners and administration of intravenous spasmolytics (see section below) may also help. However, despite these strategies, suboptimal distension is unfortunately frequently encountered in day-to-day clinical practice. 

Once the supine study has been acquired, the rectal catheter is left in situ and the patient asked to turn prone. A second scout is performed and if distension is deemed suboptimal, the pressure limit will be increased to 25 mm Hg to encourage further gas insufflation. A further scout is performed and when this demonstrates optimal insufflation, the second study is acquired. The examination is then complete and the rectal catheter removed. The patient is reassured that much of the insufflated gas will be absorbed (rather than expelled), and that any abdominal cramping should ease within a few minutes. 

Colonic folds can be particularly complex, particularly in the flexures and rectum. Fused folds are common in these locations (Fig. 14.5). Fused folds are simply recognized by their three-dimensional shape. Occasionally one may visualize focal thickening within a fold. Folds can be distinguished from polyps due to the obtuse margins, internal attenuation (which will often contain some fat) and the non-focality of the lesion. Thickened folds are usually seen in regions of suboptimal colonic distension, so comparison with the complementary dataset in a different position with improved distention will frequently assist in the identification of thickened folds (Fig. 14.6). 

---