Magnification with chromoendoscopy is the most reliable method to determine whether colorectal lesions are neoplastic or not

We have read the article of Sonwalkar et al. with great interest [1]. They conducted a noncomparative retrospective study to assess the differential diagnostic accuracy of nonmagnifying chromoendoscopy for pit pattern analysis, and concluded that nonmagnifying chromoendoscopy can be used to distinguish neoplastic from nonneoplastic colonic polyps.

We routinely use magnifying colonoscopy for examination as it provides not only the conventional view but also a magnified one for observation after dye spraying for histology prediction on the basis of pit patterns [2]. As the authors mention in their discussion, we conducted a retrospective study to assess the diagnostic potential of pit patterns for histology prediction [2]. As the result was not as satisfactory as expected because of the biased retrospective design, we conducted a prospective study to make sure [3]. The overall diagnostic accuracy was as high as 99.1 %, and we therefore reported that magnifying colonoscopy could be used by well-trained colonoscopists as a nonbiopsy technique for differentiating neoplastic from nonneoplastic polyps. Moreover, as lesions are often initially diagnosed by the conventional view, and are then evaluated by chromoendoscopy with magnification followed by chromoendoscopy during magnifying colonoscopic examinations, we have conducted a second comparative prospective study to clarify whether spraying dye and using magnification at each step confers any improvement in comparison with the conventional view [4]. The overall diagnostic accuracy of chromoendoscopy with magnification was 95.6 %, which was 10 % greater than the conventional view and 5 % greater than chromoendoscopy without magnification. For this reason, we conclude that chromoendoscopy with magnification is the most reliable method by which to determine whether a colorectal lesion is neoplastic or nonneoplastic. It is true that, if nonmagnification could provide the same result as magnification for pit pattern analysis, it would be much more effective and convenient. Interestingly, our diagnostic accuracy with chromoendoscopy before magnification was similar to the results of Sonwalkar et al. using nonmagnifying colonoscopy; however, we found that additional magnification provided significantly better diagnostic accuracy. Thus, nonmagnification colonoscopy seems to be insufficient for pit pattern analysis and would result in wasting of resources or in an increase in complications for patients due to unnecessary endoscopic resection or to undertreatment.

The marginal difference in diagnostic accuracy between our two prospective studies can be explained by the fact that the second one only included lesions 10 mm in size or smaller, as most lesions larger than 10 mm are neoplastic and most lesions encountered at colonoscopy are 10 mm or less. Furthermore, even if lesions 10 mm or larger are diagnosed as hyperplastic polyps, they should be removed, as this kind of large hyperplastic polyp is considered to be a precursor of colorectal cancers with DNA methylation and deficient DNA mismatch repair, which predominantly occur in the right-sided colon [5]. Most nonneoplastic polyps larger than 10 mm are hyperplastic, and large hyperplastic polyps are reported to make up less than 1 % of hyperplastic polyps. Surprisingly, Sonwalkar et al. included in their study 192 nonneoplastic lesions investigated endoscopically, of which an extremely high proportion (74 lesions, or 38.5 %) were endoscopically judged to be nonneoplastic. We wonder if the retrospective nature of the study biased its conclusions, and we would also be greatly interested in the clinicopathological characteristics of these large nonneoplastic lesions, including their location and final histology.

Interobserver and intraobserver consistency in the endoscopic assessment of colonic pit patterns have been reported to be good when the examinations are performed by experienced endoscopists [6]. Although only one expert colonoscopist was included in our first prospective study, two colonoscopists who are familiar with magnifying colonoscopy were included in the second. There was no significant difference between the two examiners in their overall diagnostic accuracy using each method. In the study by Sonwalkar et al., an experienced consultant and a trainee performed the colonoscopies; although both were described as having a good knowledge of pit pattern recognition, no difference between them was mentioned.

References

• 1 Sonwalkar S, Rotimi O, Rembacken B J. Characterization of colonic polyps at conventional (nonmagnifying) colonoscopy after spraying with 0.2 % indigo carmine dye.  Endoscopy. 2006;  38 1218-1223
• 2 Kato S, Fujii T, Koba I. et al . Assessment of colorectal lesions using magnifying colonoscopy and mucosal dye spraying: can significant lesions be distinguished?.  Endoscopy. 2001;  33 306-310
• 3 Kato S, Fu K I, Sano Y. et al . Magnifying colonoscopy as a non-biopsy technique for differential diagnosis of non-neoplastic and neoplastic lesions.  World J Gastroenterol. 2006;  12 1416-1420
• 4 Fu K I, Sano Y, Kato S. et al . Chromoendoscopy using indigo carmine dye spraying with magnifying observation is the most reliable method for differential diagnosis between non-neoplastic and neoplastic colorectal lesions: a prospective study.  Endoscopy. 2004;  36 1089-1093
• 5 Jass J R, Whitehall V L, Young J, Leggett B A. Emerging concepts in colorectal neoplasia.  Gastroenterology. 2002;  123 862-876
• 6 Huang Q, Fukami N, Kashida H. et al . Interobserver and intra-observer consistency in the endoscopic assessment of colonic pit patterns.  Gastrointest Endosc. 2004;  60 520-526