Is routine endoanal ultrasound useful in anal fistulas?

To evaluate the effectiveness of endoanal ultrasound with hydrogen peroxide enhancement in the assessment of anal fistula (tract and internal opening), and to value the utility of this examination for anal or perianal suppuration when performed by a colorectal surgeon trained in this technique.

Endoanal ultrasound was performed in 103 patients with anal or perianal suppuration. Twenty patients were excluded: 9 had the external opening closed, and 11 had cryptoglandular abscesses. All ultrasound scans were performed by the same explorer using a BK Diagnostic Ultrasound System with a 7 MHz endoprobe. The examination was based on the identification of the three anal planes, then hydrogen peroxide was infused and the procedure was repeated.

Out of 83 patients included, 11 had a perianal sinus and 72 an anal fistula. In all fistulas the main tract was found: 24 were inter-sphinteric (33.33%), 33 trans-sphincteric (45.83%), 3 supra-sphincteric (4.17%), and 12 extra-sphincteric (16.67%). An internal opening was identified in 69 (95.83%).

Endoanal ultrasound with hydrogen peroxide enhancement is an effective examination to visualize fistulous tracts and internal openings. We think it is highly useful for anal or perianal suppuration to identify abscesses, to recognize a perianal sinus, to check the sphincteric condition, and to plan subsequent surgery.