Endoanal ultrasound for preoperative evaluation of perianal sepsis

Endoanal ultrasound (EUS) imaging performed with a 10-MHz rotating probe can be easily performed by surgeons in the office or the operating room. The procedure is well tolerated, easily repeatable, and cost effective. Major indications are perianal sepsis, fecal incontinence, and anorectal malignancies. Whether used for the evaluation of malignant or benign disease, this technique has been shown to be accurate in identifying normal anatomy and anatomic alterations. EUS has shown higher accuracy than physical examination in localizing the internal opening and in detecting horseshoe extension of anal fistulas. Compared with MRI, EUS demonstrated similar sensitivity but lower specificity at detecting perianal fistulas; however data from the literature are heterogeneous and no definitive conclusion can be made. The costs for MRI are higher and not all hospitals have the facility. A total of 934 EUS examinations were performed in our Unit for perianal sepsis from January 2007 to September 2013, we found an intersphincteric abscess, a transsphincteric fistula, and a horseshoe extension in 54%, 32%, and 8% of cases, respectively. Overall accuracy in identifying the internal opening was over 90%. In conclusion, EUS is a reliable and reproducible method for preoperative assessment of anorectal diseases, at present it should be consider the diagnostic tool of choice for patients with perianal sepsis.