title: Endoanal ultrasound or magnetic resonance imaging for preoperative assessment of anal fistula: a comparative study.
abstract: OBJECTIVE
  To compare endoanal ultrasound (EUS) with a 10-MHz probe vs. bodycoil magnetic resonance imaging (MRI) in the preoperative evaluation of anal fistula.
  
  
  METHODS
  23 patients with fistula in the anal region underwent preoperative 0.5 T bodycoil MRI and 10 MHz EUS which included probing in 6 patients. The results of the EUS and MRI were compared against the surgical findings as a reference method.
  
  
  RESULTS
  In classification of the primary tract there was agreement between EUS and surgical findings in 14 (61%) and between MRI and surgery in 11 (48%). Concerning the presence of an internal opening the corresponding figures were 17 (74%) and 10 (43%) and in judging the presence of an extension or an abscess 15 (65%) vs. 11 (48%), respectively. In three out of eight patients with nonhealing or recurrence after surgery preoperative imaging had shown an extension and/or an abscess that was not identified by the surgeon.
  
  
  CONCLUSIONS
  EUS, sometimes complemented with probing, is well comparable to bodycoil MRI in classifying and describing the topography of an anal fistula.
authors.affiliation: Department of Surgery, University Hospital, Uppsala, Sweden. agneta.westerfelt@kirurgi.uu.se
authors.forename: U M
authors.initials: UM
authors.lastname: Gustafsson
authors.forename: B
authors.initials: B
authors.lastname: Kahvecioglu
authors.forename: G
authors.initials: G
authors.lastname: Aström
authors.forename: H
authors.initials: H
authors.lastname: Ahlström
authors.forename: W
authors.initials: W
authors.lastname: Graf