An incomplete colonoscopy examination may occur in up to 5-10 percent of cases and may be due to patient discomfort, a colon with many twists, postoperative adhesions, or hernias. Traditionally, double-contrast barium enema has been used to evaluate the colon in these situations. However, after an incomplete colonoscopy, a double-contrast barium enema may be difficult to perform because of air blockage from gas remaining from the recently performed colonoscopy. In addition, fluid left from a polyethylene glycol preparation may prevent optimal coating of the colon wall with barium.
Two studies have demonstrated the usefulness of virtual colonoscopy after an incomplete traditional colonoscopy (47, 48). In one of these studies, virtual colonoscopy was better able to evaluate the colon than was a barium enema (47). A virtual colonoscopy performed on the same day as an incomplete colonoscopy takes advantage of the single bowel preparation and the fact that the colon is often well distended with gas from the previous colonoscopy, thus requiring only a small amount of additional gas to be pumped in. In this situation, the virtual colonoscopy is clearly better tolerated than a double-contrast barium enema (47).