title: Computer-assisted evaluation of perianal fistula activity by means of anal ultrasound in patients with Crohn's disease.
abstract: OBJECTIVE
  Assessment of the activity of perianal fistulas may be of clinical relevance in patients with Crohn's disease. Fistula activity is currently evaluated by means of magnetic resonance imaging; anal ultrasound can also be used, but its diagnostic performance in this setting remains to be defined. Our aims were to evaluate the agreement between clinical examination, magnetic resonance imaging, and anal ultrasound in assessing perianal fistula activity, and to apply computerized analysis to improve the assessment of ultrasound images.
  
  
  METHODS
  Thirty-one consecutive patients with Crohn's perianal fistulas underwent clinical examination, and magnetic resonance and anal ultrasound imaging. Active fistulas were defined as the presence of active drainage or signs of local inflammation on clinical examination, and the definition was confirmed by surgical examination. Activity was assessed on the basis of T2 hyperintensity on magnetic resonance imaging and the degree of hypoechogenicity on anal ultrasound; the anal ultrasound images were also analyzed using dedicated computer image-analysis software.
  
  
  RESULTS
  Twenty-five patients had an active fistula at clinical examination. The agreement between clinical examination and magnetic resonance imaging was good (k-value = 0.739), whereas that with anal ultrasound was only fair (k-value = 0.266-0.294); computer-assisted analysis of the anal ultrasound images improved the agreement from fair to good (k-value = 0.608-0.670).
  
  
  CONCLUSIONS
  Anal ultrasound can be used to assess fistula track activity in patients with Crohn's disease. The diagnostic performance of the technique can be improved to values comparable with those of magnetic resonance imaging by using a computer-assisted evaluation of the anal ultrasound images.
authors.affiliation: Post-graduate School of Gastroenterology and Digestive Endoscopy (I), University of Milan, Milan, Italy.
authors.forename: Flavio
authors.initials: F
authors.lastname: Caprioli
authors.forename: Alessandra
authors.initials: A
authors.lastname: Losco
authors.forename: Chiara
authors.initials: C
authors.lastname: Viganò
authors.forename: Dario
authors.initials: D
authors.lastname: Conte
authors.forename: Pietro
authors.initials: P
authors.lastname: Biondetti
authors.forename: Laura V
authors.initials: LV
authors.lastname: Forzenigo
authors.forename: Guido
authors.initials: G
authors.lastname: Basilisco
mesh_terms: D000328:Adult; D000368:Aged; D001004:Anus Diseases / Q000000981:diagnostic imaging*; D003424:Crohn Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012003:Rectal Fistula / Q000000981:diagnostic imaging*; D018709:Statistics, Nonparametric; D014463:Ultrasonography