Contrast‐Enhanced endosonography for the diagnosis of anal and anovaginal fistulas

Purpose We assessed whether contrast-enhanced anal endosonography (AES) with hydrogen peroxide improves the identification of anal fistulas and their internal openings compared with non-contrast AES. Methods The study group comprised 12 patients who had various types of anal fistulas with visible external openings. AES was performed before and about 15 seconds after injection of 1 ml of 3% hydrogen peroxide into the fistula tract through the external opening. Results Both contrast and non-contrast AES revealed 7 transsphincteric, 2 intersphincteric, 1 suprasphincteric, and 2 anovaginal fistulas. Simple tracts were found in 8 cases and complex tracts in 4 cases on non-contrast AES. Contrast-enhanced AES revealed 9 simple and 3 complex fistulas. One fistula that appeared complex on the non-contrast study appeared simple after contrast agent administration. Contrast-enhanced AES demonstrated more internal openings than non-contrast AES did. Surgery confirmed 11 of the fistulas; an internal opening could not be located surgically for the other tract. Conclusions Contrast-enhanced AES appears to be superior to non-contrast AES in the preoperative assessment of anal and anovaginal fistulas and in demonstrating and locating their internal openings. © 2002 Wiley Periodicals, Inc. J Clin Ultrasound 30:145–150, 2002; DOI 10.1002/jcu.10042