Objective: This study was designed to evaluate the effectiveness of hydrogen peroxide-enhanced endoanal ultrasound in identification of the internal opening and fistulous tract of cases of fistula-in-ano and compare the ultrasonographic results with Goodsall's rule and the surgical outcomes.
Material and Methods: A total of 21 patients diagnosed with anal fistula in Songklanagarind Hospital from November 2004- August 2005 were reviewed, comparing endoanal ultrasound enhanced with hydrogen peroxide with operative notes and Goodsall's rule. All endoanal ultrasounds were performed by the same colorectal surgeon.
Results: In 95% of the cases, the internal opening was identified. In only one case was the surgeon unable to obtain sufficient information about the internal opening. In 100% of the cases the tract and its type were identified. The accuracy for Goodsall's rule was 58.82%.
Conclusion: The accuracy of hydrogen peroxide-enhanced anal endosonography for the identification of internal openings and information on the fistulous tract was sufficient to justify preoperative endosonography as a diagnostic method for routine use in patients with fistula-in-ano.