title: Differentiation of perianal fistulas with digital subtraction magnetic resonance fistulography.
abstract: BACKGROUND
  Pelvic magnetic resonance imaging (MRI) is accurate in identifying perianal fistulas. The exact visualization of fistulous tracts and concomitant abscesses determine the type of treatment. To improve the detection of perianal fistulas, we studied digital subtraction MR-fistulography for tissue differentiation based on signal intensity measurements.
  
  
  METHODS
  This study included 75 patients with the clinical diagnosis of perianal fistula. All patients were analyzed by a thin-slice, high-resolution, fast low-angle shot 3-dimensional sequence in the axial plane before and after intravenous injection of gadobenate dimeglumine, followed by image subtraction. Operator-defined regions of interest were used to calculate signal intensities of the inflamed fibrous walls of fistulas, the common femoral artery, the internal and external sphincter muscles, and the gluteus muscle. The fistulas were classified according to Parks classification.
  
  
  RESULTS
  Based on signal intensity measurements in 75 patients with perianal fistulas, diagnosed by digital subtraction MR-fistulography, a significant differentiation between fistulous tracts and anatomic structures was possible. MRI identified 116 perianal fistulas (34 intersphincteric, 33 transsphincteric, 10 suprasphincteric, and 39 extrasphincteric) and 35 abscesses.
  
  
  CONCLUSIONS
  Digital subtraction MR-fistulography is a new, promising, noninvasive imaging technique for the detection of perianal fistulas and abscesses.
authors.affiliation: Department of Radiology, University Hospital of Freiburg, Freiburg, Germany. schaefer@mrs1@ukl.uni-freiburg.de
authors.forename: Oliver
authors.initials: O
authors.lastname: Schaefer
authors.forename: Christian
authors.initials: C
authors.lastname: Lohrmann
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kreisel
authors.forename: Jens
authors.initials: J
authors.lastname: Rasenack
authors.forename: Guenther
authors.initials: G
authors.lastname: Ruf
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hopt
authors.forename: Mathias
authors.initials: M
authors.lastname: Langer
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001003:Anal Canal / Q000473:pathology; D002081:Buttocks / Q000473:pathology; D002648:Child; D003287:Contrast Media; D005260:Female; D005263:Femoral Artery / Q000473:pathology; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology; D009942:Organometallic Compounds; D012003:Rectal Fistula / Q000473:pathology*; D013382:Subtraction Technique
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C064572:gadobenic acid; D008536:Meglumine