Role of Transcutaneous Perianal Ultrasonography in Evaluation of Fistulas In Ano

Abstract

OBJECTIVE: The purpose of this study was to evaluate the role of transcutaneous perianal ultrasonography in evaluation of fistulas in ano and to assess its possible role as a first-line investigation, for follow-up, and as a possible substitute for magnetic resonance imaging. METHODS: Transcutaneous perianal ultrasonography was performed in 30 patients with fistulas in ano with the use of a 3- to 6-MHz sector probe, a 7- to 11-MHz linear probe, and a 5- to 7-MHz endocavitary probe. Patients were followed clinically and at surgery to assess the accuracy of transcutaneous perianal ultrasonography. RESULTS: A total of 43 fistulas, sinus tracts, or both were found in 26 patients. They appeared as hypoechoic tracts. Eleven of 30 patients had the presence of a collection or abscess, which appeared as hypoechoic areas. Twenty-four of 29 patients with positive findings underwent surgery. In these, 35 of 39 tracts were surgically confirmed (positive predictive value, 90%). The positive predictive value for demonstration of an internal opening was 85% (22/26) when compared with direct visualization or probing. Sensitivity for detection of tracts was 100%, and that for demonstration of an internal opening was 96% (26/27). The negative predictive value for sinus/fistulous tracts was nearly 100%. Transcutaneous perianal ultrasonography could not adequately evaluate suprasphincteric-type fistulas. However, it is a good, inexpensive modality in the evaluation of patients with fistulas in ano and also helps in follow-up of these patients. It can also be used to select patients who need magnetic resonance imaging. CONCLUSIONS: Transcutaneous perianal ultrasonography has the potential to become the first investigation in patients with perianal fistulas and abscesses.