Contrast-enhanced endoanal and transperineal sonography in perianal fistulas.

Background/aims: To improve the diagnostic potential of ultrasound in patients with perianal fistulas, by performing a combined perineal and endorectal Doppler sonography investigation before and after contrast enhancement with hydrogen peroxide.

Methodology: Ten patients (9 male and 1 female) with perianal fistulas were tested. After contrast-free transperineal and endoanal sonography, hydrogen peroxide was injected in the fistulas and the ultrasound examinations were repeated.

Results: All fistulas were identified by conventional endoanal and transperineal sonography. The contrast application gave more detailed information about the location of the fistula in relation to the anal lumen and sphincters. The fistulas were distributed as follows: intersphincteric - in 5 patients, transsphincteric - in 2 and extrasphincteric complicated (with 1 or more secondary tracks) fistula - in 3 patients. The findings have been confirmed intraoperatively in 9 patients that underwent an operation. Hypervascularization of the wall was detected in 4 patients by means of Doppler investigation which also differentiated arterial blood flow in 3 cases and venous blood flow in one.

Conclusions: The application of the contrast-enhanced endoanal and transperineal sonography offers a more detailed perianal fistula imaging. In addition the Doppler technique can further characterize their blood supply.