Chromoscopic colonoscopy enhances polyp detection compared with conventional colonoscopy

Colonoscopy is a diagnostic test that enables small growths in the bowel (polyps) to be detected. These lesions can develop into cancer in approximately 5% of the cases. Although the test is the most sensitive test that exists for the detection of these growths, some may be missed. If a simple dye spraying technique (chromoscopy) is used with the colonoscopic test, the detection of these lesions may be enhanced. Several studies have examined the effect of chromoscopy on enhancing polyp detection but the data is inconsistent. This review investigated whether chromoscopy can enhance polyp detection compared with conventional colonoscopy.

Five randomised trials with a total of 1059 participants were included. Despite differences within the study designs there appears to be strong evidence that chromoscopic colonoscopy enhances the detection of polyps in the colon and rectum.  

Authors' conclusions: 

There appears to be strong evidence that chromoscopy enhances the detection of neoplasia in the colon and rectum. Patients with neoplastic polyps, particularly those with multiple polyps, are at increased risk of developing colorectal cancer. Such lesions, which presumably would be missed with conventional colonoscopy, could contribute to the interval cancer numbers on any surveillance programme.

Read the full abstract...

Although conventional colonoscopy is the most sensitive test available for the investigation of the colorectum for polyps, there are data that raise concerns about its sensitivity. Chromoscopy may be one way of enhancing the ability for colonoscopy to detect polyps particularly diminutive flat lesions that may be otherwise difficult to detect.


To determine whether the use of chromoscopy enhances detection of polyps and neoplasia during endoscopic examination of the colon and rectum.

Search strategy: 

MEDLINE, EMBASE and the Cochrane Library databases were searched (April 2010) along with a hand search of abstracts from relevant meetings. Search terms included randomised trials containing combinations of the following: 'chromoscopy' 'colonoscopy' 'dye-spray' 'chromo-endoscopy' 'indigo-carmine' 'magnifying endoscopy'.

Selection criteria: 

All prospective randomised trials comparing chromoscopic with conventional endoscopic examination of the lower gastrointestinal tract were included. Patients with inflammatory bowel disease or polyposis syndromes were excluded.

Data collection and analysis: 

Two reviewers assessed the methodological quality of potentially eligible trials and independently extracted data from the included trials. Outcome measures included the detection of polyps (neoplastic and non-neoplastic), the detection of diminutive lesions, the number of patients with multiple neoplastic lesions and the extubation time.

Main results: 

Five trials were included in this update, and although there were some methodological drawbacks and differences in study design, combining the results showed a significant difference in favour of chromoscopy for all detection outcomes. In particular, chromoscopy is likely to yield significantly more patients with at least one neoplastic lesion (OR 1.67 (CI 1.29-2.15)) and significantly more patients with three or more neoplastic lesions (OR 2.55 (CI 1.49-4.36)). Not surprisingly the withdrawal times were significantly slower for the chromoscopy group.