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Acetic acid spray in colonoscopy: an alternative to chromoendoscopy
  1. Y J Kawamura,
  2. K Togashi,
  3. J Sasaki,
  4. F Konishi
  1. Jichi Medical School, Saitama, Japan
  1. Correspondence to:
    Dr Y J Kawamura
    Jichi Medical School, 1-847, Amanuma-cho, Omiya-ku, Saitama-shi, Saitama 3308503, Japan;

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We read with interest the article by Rutter et al (Gut 2004;53:256–60) and the letter in response to this article by Hata et al (Gut 2004;53:1722). Rutter demonstrated the advantage of magnifying chromoendoscopy using indigo carmine for detection of dysplasia compared with conventional colonoscopy without dye spray by back to back colonoscopy in patients with longstanding ulcerative colitis.

Hata et al discussed the characteristics and correct selection of dyes. In particular, Hata et al emphasised that there are two types of dye spraying: the contrast method in which dye is used solely to contrast the irregularity of the surface, and the staining method in which dyes such as crystal violet and methylene blue are used to stain the colonic mucosa. The latter technique provides more detailed structure of neoplastic as well as non-neoplastic colonic mucosa, which may contribute to more precise diagnosis of dysplasia and inflammatory change than the contrast method.

However, as Hata et al pointed out, a disadvantage of the staining method is that it is time consuming. Usually, it takes two or three minutes to stain one region. Therefore, it would be beneficial if there were an agent that demonstrated the fine structure of the colonic mucosa without a delay.

Recently, we have introduced acetic acid spray in screening colonoscopy to visualise the fine structure of colonic neoplasia, in which approximately 5 ml of 2% acetic acid solution is sprayed towards the targeted lesion in the same manner as for indigo carmine. The advantages of using acetic acid spray as a staining method are as follows. Firstly, the fine structure of the mucosa can be demonstrated immediately (fig 1A, 1B). Therefore, it reduces the time for examination, especially in patients with multiple lesions. Secondly, acetic acid effectively removes surface mucous material that interferes with magnifying observations (fig 1C, 1D). Lastly, acetic acid is less expensive.

Figure 1

 (A) Magnifying chromoendoscopy using the contrast method. Indigo carmine spray reveals a neoplastic pattern. However, the pit pattern cannot be observed in some parts of the tumour. (B) After acetic acid spray, the detailed structure of the entire surface is immediately demonstrated more meticulously than with the contrast method. (C) Polyp covered with mucus. Dye spray using indigo carmine fails to reveal the surface structure because of the mucus. (D) After acetic acid spray, the mucous has been clearly removed and the surface of the polyp can be evaluated.

We agree with Hata et al that it is essential to understand the various methods of dye spray and to apply them appropriately, according to the situation. Here, we advocate acetic acid spray as an alternative to dye spray for enhancing the fine structure of the mucosa. Hata et al titled their letter “To dye or not to dye. That is beyond question!” We would like to add “To spray dye or to spray acetic acid. That is our question!


  • Conflict of interest: None declared.

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