Ultrasound study of anal fistulas with hydrogen peroxide enhancement

PURPOSE: This study was designed to evaluate the effectiveness of hydrogen peroxide-enhanced, endoanal ultrasound in the assessment of fistula-in-ano and compare ultrasonographic results with the surgical outcome. METHODS: A total of 80 patients with anal fistula were studied prospectively by physical examination and endoanal ultrasound enhanced with hydrogen peroxide. We used standarized ultrasonography and operation notes. The results of these studies were compared with the surgical findings. The ultrasonographic study of the anal canal describes the fistula's characteristics, which provides an ultrasonographic classification of the fistula. All endoanal ultrasounds were performed by colorectal surgeons. RESULTS: In 94 percent of the cases, the internal opening was identified. In only one case were we unable to obtain sufficient information about the tract and the fistula's level. The endoanal ultrasound was able to correctly identify whether the tract was linear or curvilinear in 95 percent of the cases. The ultrasound level coincided with surgical findings in 85 percent of patients, and chronic fistula cavities were confirmed by surgery in 75 percent of patients. CONCLUSIONS: The use of endoanal ultrasound, with hydrogen peroxide enhancement, by a colorectal surgeon with adequate experience in endoanal ultrasound provides excellent results in the presurgical examination of fistula-in-ano.