title: Transperineal ultrasonography as a complementary diagnostic tool in identifying acute perianal sepsis.
abstract: BACKGROUND
  Successful anal fistula care in complex cases can be assisted by specialized imaging which accurately defines the site of the internal fistula opening and the fistula type. There are currently limited data concerning the clinical indications for and accuracy of transperineal ultrasound (TP-US) in acute perianal sepsis. The aims of this study were to compare the anatomical interpretation of TP-US images with magnetic resonance imaging (MRI) and surgical findings in an unselected patient cohort presenting with acute perianal sepsis.
  
  
  METHODS
  Sixty-seven consecutive patients with acute anorectal sepsis referred from the surgical department were examined using TP-US and Gadolinium-enhanced MRI with both examiners blinded to the surgical results. Fistulae were categorized by the Parks' classification of fistula type.
  
  
  RESULTS
  Thirty-six abscesses were detected by MRI, 38 by TP-US and 30 by surgical examination. Operatively discordant cases showed only ischiorectal panniculitis. TP-US was more accurate in the diagnosis of superficial sepsis and MRI in the diagnosis of deep-seated perirectal infection. TP-US and MRI show concordance with operative findings in fistula diagnosis with a tendency for TP-US to overdiagnose trans-sphincteric fistulae and MRI to over diagnose extra-sphincteric fistulae. Comparison of TP-US with MRI showed good agreement for perianal abscess diagnosis (τ = 0.82) and for fistula diagnosis (τ = 0.68). For fistulae, TP-US showed moderate agreement with surgery (τ = 0.43) with only fair agreement between MRI and surgery (τ = 0.29).
  
  
  CONCLUSIONS
  Transperineal ultrasound complements other imaging modalities in the anatomical diagnosis of acute perianal abscesses and fistulae. It has specific advantages over other techniques and is accurate in the detection of superficially located perirectal sepsis showing concordance with MRI and surgical findings.
authors.affiliation: Department of Radiology, Innsbruck Medical University, Anichstrasse 35, 6020, Innsbruck, Austria, michaela.plaikner@i-med.ac.at.
authors.forename: M
authors.initials: M
authors.lastname: Plaikner
authors.forename: A
authors.initials: A
authors.lastname: Loizides
authors.forename: S
authors.initials: S
authors.lastname: Peer
authors.forename: F
authors.initials: F
authors.lastname: Aigner
authors.forename: D
authors.initials: D
authors.lastname: Pecival
authors.forename: A
authors.initials: A
authors.lastname: Zbar
authors.forename: C
authors.initials: C
authors.lastname: Kremser
authors.forename: H
authors.initials: H
authors.lastname: Gruber
mesh_terms: D000038:Abscess / Q000000981:diagnostic imaging* / Q000209:etiology / Q000601:surgery; D000328:Adult; D001003:Anal Canal / Q000000981:diagnostic imaging*; D003287:Contrast Media; D005260:Female; D005682:Gadolinium; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D010502:Perineum / Q000000981:diagnostic imaging; D012003:Rectal Fistula / Q000150:complications / Q000000981:diagnostic imaging* / Q000601:surgery; D012189:Retrospective Studies; D014463:Ultrasonography
chemical_list: D003287:Contrast Media; D005682:Gadolinium