Efficacy of total colonoscopy with a transparent cap in comparison with colonoscopy without the cap

In spite of scrupulous inspection during routine colonoscopy, small lesions behind the semilunar folds can be situated in blind spots, where they are easily overlooked. The aim of this study was to evaluate the efficacy of total colonoscopy with a transparent cap in identifying such lesions, in comparison with colonoscopy without the cap.

In 24 patients with colorectal polyps, tandem colonoscopic procedures were carried out on the same day in random order, first without a transparent cap and then with the cap (without-to-with), or first with the cap and then without the cap (with-to-without). The time required for intubation as far as the cecum, the number of polyps detected, and procedure-related complications were recorded. The frequencies of terminal ileal intubation and retroflexion within the rectum were also recorded.

Total colonoscopy was carried out in all of the patients without any complications. Colonoscopy with a transparent cap ensured good visual fields during insertion and withdrawal of the colonoscope. There were no significant differences in the intubation time to the cecum or in the frequency of terminal ileal intubation between the two procedures. The miss rate for polyps was 15% in without-to-with tandem colonoscopies, and zero in with-to-without procedures (P = 0.0125). The diameter of all the missed polyps except for one lesion (8 mm) was less than 5 mm. Retroflexion within the rectum was more difficult using the colonoscope with the cap (P < 0.0001), and was successful in only one case using the cap.

Total colonoscopy with a transparent cap allows inspection of the blind area of the colonic mucosa behind the semilunar folds, with good visual fields. This method is potentially useful for both screening and diagnostic purposes.