The use of different diagnostic modalities in diagnosing fistula-in-ano

In this study, a comparison was made of the accuracy and clinical usefulness of clinical investigation, fistulography, and endorectal ultrasound with and without hydrogen peroxide in preoperative classification of the fistula-in-ano.

Forty patients with perianal fistulas that were preoperatively investigated with clinical investigation, fistulography, or endoanal ultrasound with/without hydrogen peroxide were included in the study. The fistula classification obtained by different diagnostic modalities was compared with the definite surgical classification. The investigators were blinded to the results of other investigations.

Ultrasound with H2O2 had the highest classification accuracy among all methods used, compared with surgical examination during operation (72.5%). Kappa statistics found good agreement only between ultrasound with H2O2 (0.592), which was statistically significant (p<0.001). Secondary extension was found in 8 patients (20%). The classification accuracy was the same for ultrasound with and without H2O2 (82.5%). The highest kappa value (0.475) was found with ultrasound with H2O2 (p=0.008). With surgical examination 24 low and 9 high transsphincteric fistulas were found. The classification accuracy was highest for endorectal ultrasound with H2O2 (85%). Kappa values were good only for endorectal ultrasound with H2O2 which was statistically significant (p=0.001).

In this study, endorectal ultrasound with H2O2 was the most accurate diagnostic modality in the preoperative assessment of the fistula-in-ano. As it can provide valuable information that can influence the type of operative procedure, and because it is relatively cheap and available in almost all hospitals, it should be used prior to operative treatment in all patients with a fistula-in-ano.