title: Diffusion-weighted MR imaging for the diagnosis of abscess complicating fistula-in-ano: preliminary experience.
abstract: OBJECTIVE
  To investigate the role of diffusion-weighted magnetic resonance imaging (DWMRI) in the diagnosis of abscess-complicating fistula-in-ano.
  
  
  METHODS
  This retrospective study was approved by our Institutional Review Board and informed consent was waived. MRI examinations, including fat-suppressed T2-weighted turbo spin-echo (T2-TSE) MRI and DWMRI, of 24 patients with a fistula-in-ano, were reviewed by two independent readers for the presence and number of visible fistulas, conspicuity and apparent diffusion coefficient (ADC) measurement of suspected fistula tracks and pelvic collections. The reference standard was surgical with follow-up findings.
  
  
  RESULTS
  Sensitivity was 91.2 % [95 % CI: 76 %-98 %] for T2-weighted TSE MRI and 100 % [95 % CI: 90 %-100 %] for DWMRI detecting fistulas. ADC values were lower in abscesses than in inflammatory masses (P = 0.714.10(-6)). The area under the ROC curve was 0.971 and the optimal cut-off ADC value was 1.186 × 10(-3) mm(2)/s, yielding a sensitivity of 100 % [95 % CI: 77 %-100 %], a specificity of 90 % [95 % CI: 66 %-100 %], a positive predictive value of 93 % [95 % CI: 82.8 %-100 %] and a negative predictive value of 90 % [95 % CI: 78 %-100 %] for an abscess diagnosis. Fistula conspicuity was greater with DWMRI than with T2-TSE MRI for the two observers (P = 0.0034 and P = 0.0007).
  
  
  CONCLUSIONS
  DWMRI shows high sensitivity and specificity for the diagnosis of perianal abscesses and helps discriminate between an abscess and inflammatory mass. Conspicuity of fistulas-in-ano is greater with DWMRI than with T2-weighted TSE MRI.
  
  
  CONCLUSIONS
  • DWMRI can differentiate between pelvic abscess and inflammatory mass. • DWMRI helps avoid gadolinium-chelate administration in patients with a suspected fistula-in-ano. • DWMRI provides high degrees of conspicuity for fistula-in-ano. • Conspicuity of fistulas is better with DWMRI imaging than with T2-TSE-weighted MRI.
authors.affiliation: Department of Body and Interventional Imaging, Hôpital Lariboisière, Assistance Publique-Hôpitaux de Paris, 2 rue Ambroise Paré, 75475, Paris Cedex 10, France, anthony.dohan@lrb.aphp.fr.
authors.forename: Anthony
authors.initials: A
authors.lastname: Dohan
authors.forename: Clarisse
authors.initials: C
authors.lastname: Eveno
authors.forename: Raluca
authors.initials: R
authors.lastname: Oprea
authors.forename: Karine
authors.initials: K
authors.lastname: Pautrat
authors.forename: Vinciane
authors.initials: V
authors.lastname: Placé
authors.forename: Marc
authors.initials: M
authors.lastname: Pocard
authors.forename: Christine
authors.initials: C
authors.lastname: Hoeffel
authors.forename: Mourad
authors.initials: M
authors.lastname: Boudiaf
authors.forename: Philippe
authors.initials: P
authors.lastname: Soyer
mesh_terms: D000038:Abscess / Q000175:diagnosis* / Q000209:etiology; D000328:Adult; D000368:Aged; D003287:Contrast Media; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D010388:Pelvis; D012372:ROC Curve; D012003:Rectal Fistula / Q000150:complications* / Q000175:diagnosis; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D003287:Contrast Media