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 (H₂O₂) 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 ₂O₂ 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 ₂O₂ injection was not feasible in 26 patients (43%). Visualization of 11 (31%) fistulas improved after administration of H ₂O₂. Six fistulous tracts not detected before H ₂O₂ 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. H₂O₂ injection should become an integral part of every sonographic study of perianal fistulas.