Colonoscopy, tumors, and inflammatory bowel disease

Virtual chromoscopy during colonoscopy

Narrow-band imaging (NBI) is a new technique that allows us to distinguish neoplastic and non-neoplastic lesions without chromoendoscopy, and should be very useful in detecting small or flat lesions missed by standard endoscopy. A study recently examined 148 colorectal lesions, 16 hyperplastic polyps, 84 tubular adenomas, and 48 early carcinomas [1]. Lesions were observed first under NBI magnification and then under standard magnification with chromoendoscopy. Correspondence between the two diagnostic methods was 88 % for type II, 100 % for type IIIs, 98 % for type IIIl, 88 % for type IV, 78 % for type Vi, and 100 % (3/3) for type Vn pit patterns. NBI depicted a brownish change on the basis of surface capillaries in 6 % of hyperplasia and 99 % of tubular adenomas (P < 0.005) [1] . In a second, prospective study, 180 colorectal lesions were observed with conventional colonoscopy, under low- and high-magnification NBI, and chromoendoscopy [2]. The diagnostic accuracy of NBI with low or high magnification was significantly higher than that of conventional colonoscopy (P = 0.0434 and P < 0.001), and was comparable to that of chromoendoscopy. Both low- and high-magnification NBI were capable of distinguishing neoplastic from non-neoplastic colorectal lesions [2].

A randomized controlled trial [3] of colonoscopy withdrawal in white light versus NBI in 434 patients aged 50 years was performed using high-definition, wide-angle (170° field of view) colonoscopes. There was no difference between groups in the percentage of patients with ≥ 1 adenoma for the entire cohort (white light 67 % vs. NBI 65 %; P = 0.61). The high prevalence rates of adenomas were accounted for by detection of large numbers of adenomas, including flat adenomas, which were ≤ 5 mm. For differential diagnosis of neoplastic (adenoma and adenocarcinoma) and hyperplastic polyps, the sensitivity of the conventional colonoscope for diagnosis of neoplastic polyps was 82.9 %, specificity was 80.0 %, and diagnostic accuracy was 81.8 % [4], significantly lower than those achieved with the NBI system (sensitivity 95.7 %, specificity 87.5 %, accuracy 92.7 %), and chromoendoscopy (sensitivity 95.7 %, specificity 87.5 %, accuracy 92.7 %). Therefore, no significant difference existed between the NBI system and chromoendoscopy during differential diagnosis of neoplastic and non-neoplastic polyps [4]. Moreover, pit patterns were not always identical with NBI and chromoendoscopy, so, the Kudo classification may need to be modified and revalidated before it can be used with confidence with NBI [5].

Another study compared the accuracy of NBI with standard colonoscopy in a prospective, randomized, crossover study of 42 patients with longstanding ulcerative colitis [6]. With NBI, 52 suspicious lesions were detected in 17 patients, compared with 28 suspicious lesions in 13 patients detected during conventional colonoscopy. In four patients the neoplasia was detected by both techniques, in four patients neoplasia was detected only by NBI, and in three patients neoplasia was detected only by conventional colonoscopy (P = 0.7). The sensitivity of the NBI system for the detection of patients with neoplasia seems to be comparable to conventional colonoscopy, although more suspicious lesions were found during NBI [6].

The value of combined chromoscopy and endomicroscopy was assessed for the diagnosis of intraepithelial neoplasias in a randomized controlled trial of ulcerative colitis in clinical remission [7]. In the conventional colonoscopic group (n = 73), random biopsy examinations and targeted biopsy examinations were performed. In the endomicroscopy group (n = 80), circumscribed mucosal lesions were identified by chromoscopy and evaluated for targeted biopsy examination by endomicroscopy. By using chromoscopy with endomicroscopy, 4.75-fold more neoplasias could be detected (P ≤ 0.005) than with conventional colonoscopy, although 50 % fewer biopsy specimens (P ≤ 0.008) were required. The presence of neoplastic changes could be predicted by endomicroscopy with high accuracy (sensitivity 94.7 %, specificity 98.3 %, accuracy 97.8 %). Thus, chromoscopy-guided endomicroscopy may lead to significant improvements in the clinical management of ulcerative colitis [7]. In a retrospective surveillance examination in 622 patients with ulcerative colitis, 46 patients were found to have dysplasia or colorectal cancer (CRC): 75 separate dysplastic or cancerous lesions were identified (mean 1.6 lesions per patient) [8]. In all, 38 of the 65 dysplastic lesions (58.5 %) and eight of the 10 cancers were visible to the endoscopist as 23 polyps and masses, one stricture, and 22 irregular mucosa. The per-patient sensitivities for dysplasia and for cancer were 71.8 % and 100 %, respectively. Dysplasia and cancer in ulcerative colitis are endoscopically visible in most patients and may be reliably identified during scheduled examinations in patients with chronic ulcerative colitis (CUC) undergoing surveillance with video endoscopy [8].

References

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