Ultrasound Study of Anal Fistulas With Hydrogen Peroxide Enhancement

Excerpt

To the Editor—We would like to comment on the article by Navarro-Luna and coworkers1 that was recently published in the Journal. According to their experience, H₂O₂-enhanced endoanal ultrasound provided correct information about the internal opening of anal fistulas in 91 percent of cases. The point in which the tract transversed the mucosal–submucosal complex was the criterion used to identify the internal opening. Cho² used plain ultrasound to define three criteria for the identification of internal openings: I, a root-like budding formed by the intersphincteric tract that contacts the internal sphincter; II, a root-like budding with an internal sphincteric defect; and III, a subepithelial breach connecting to the intersphincteric tract through an internal sphincteric defect. Combining these three criteria, Cho² was able to define the internal opening of the fistula in 93 percent of patients. However, when only criterion III was used, the rate of success was 10.7 percent. To explain their outstanding figures, Navarro-Luna et al.1 suggested that the relatively low figures for internal opening detection by ultrasound in published series are probably caused by an inappropriate technique. However, it seems that the accuracy of endosonography depends to a large extent on the criteria used to identify the internal opening rather than on the technique of endoanal ultrasound. In studies in which the three criteria were used, the accuracy of H₂O₂-enhanced ultrasound for detecting the internal opening was 68 percent,3 which is higher than the 62 percent reported in our study using two criteria,4 and much higher than 48 percent reported by Poen et al.,5 who used only criterion III. …