Acetic acid as an effective mucolytic in magnification with chromoendoscopy for pit patterns analysis

We have read the article of Togashi et al. with great interest [1]. They have compared the accuracy of predicting polyp histology at magnification colonoscopy using acetic acid and indigo carmine, either alone or in combination. They have shown that use of acetic acid spray instantly improves the pit pattern image during magnification chromoendoscopy and has high accuracy in the histological prediction of colorectal polyps. They state that acetic acid is particularly effective because it rapidly removes the mucus that can make pit pattern analysis difficult, and the aceto-white reaction accentuates the pit pattern. However, they have shown that acetic acid increases the accuracy more for adenomas (76 % - 94 %) than for hyperplastic polyps (92 % - 100 %).

Generally, hyperplastic polyps are found as diminutive sessile polyps especially in the rectum and sigmoid colon. Endoscopically, hyperplastic polyps rather than adenomas correspond to sessile, pale polyps with a smooth surface and a partial or complete surface covering of mucus. Therefore, if acetic acid is an effective mucolytic, as expected by the authors, it should improve the diagnostic accuracy for hyperplastic polyps rather than for adenomas.

Furthermore, the authors have shown that acetic acid alone (95 %) achieves higher accuracy overall than indigo carmine alone (83 %), although this difference did not reach statistical significance, possibly due to the small sample size. We conducted a prospective study to clarify whether using dye spraying and magnification at each step contributes to further endoscopic distinction in comparison with the conventional endoscopic view [2]. The overall diagnostic accuracy achieved with chromoendoscopy using indigo carmine with magnification was 95.6 % - significantly better (by 10 % and 5 % respectively) than the accuracy achieved with either the conventional view or with chromoendoscopy without magnification. Therefore, the result of Togashi et al. in relation to the diagnostic accuracy of indigo carmine with magnification seems to be lower than expected.

References

• 1 Togashi K, Hewett D G, Whitaker D A. et al . The use of acetic acid in magnification chromocolonoscopy for pit pattern analysis of small polyps.  Endoscopy. 2006;  38 613-616
• 2 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