Endosonographic evaluation of perianal fistulas and abscesses: comparison of two instruments and assessment of the role of hydrogen peroxide injection

Purpose: The aims of this study were to compare the performance of a mechanical radial endosonoscope and an endorectal electronic probe and to evaluate the value of hydrogen peroxide (H(2)O(2)) injection in the diagnosis of perianal fistulas.

Patients and methods: Sixty-one patients underwent clinical and endosonographic studies for suspected perianal fistulas or abscesses. Endosonography was performed using two instruments: a mechanical radial endosonoscope (Olympus GF-UM20) and an electronic endorectal probe (Hitachi EUP-R53). The patients were re-examined during and following H(2)O(2) injection using both systems.

Results: Thirty-seven fistulous tracts were visualized with the electronic endorectal probe versus only 9 with the mechanical radial endosonoscope. Four patients had anal stenosis, precluding the use of the larger electronic probe. Three fistulas were detected in these patients using the mechanical radial endosonoscope. H(2)O(2) injection was not feasible in 26 patients (43%). Visualization of 11 (31%) fistulas improved after administration of H(2)O(2). Six fistulous tracts not detected before H(2)O(2) administration were clearly visualized during injection and for several minutes thereafter.

Conclusions: Work-up of perianal fistula should be preferably performed using the endorectal electronic probe. However, the mechanical radial endoscope is preferred in patients with anal stricture. H(2)O(2) injection should become an integral part of every sonographic study of perianal fistulas.