title: A diagnostic accuracy meta-analysis of endoanal ultrasound and MRI for perianal fistula assessment.
abstract: BACKGROUND
  Imaging modalities such as endoanal ultrasound or MRI can be useful preoperative adjuncts before the appropriate surgical intervention for perianal fistulas.
  
  
  OBJECTIVE
  We present a systematic review of published literature comparing endoanal ultrasound with MRI for the assessment of idiopathic and Crohn's perianal fistulas.
  
  
  METHODS
  A meta-analysis was performed to obtain pooled values for specificity and sensitivity.
  
  
  METHODS
  Electronic databases were searched from January 1970 to October 2010 for published studies.
  
  
  METHODS
  Four studies were used in our analysis. There were 241 fistulas in the ultrasound group and 240 in the magnetic resonance group.
  
  
  RESULTS
  The combined sensitivity and specificity of magnetic resonance for fistula detection were 0.87 (95% CI: 0.63-0.96) and 0.69 (95% CI: 0.51-0.82). There was a high degree of heterogeneity between studies reporting on MRI sensitivity (df = 3, I = 93%). This compares to a sensitivity and specificity for endoanal ultrasound of 0.87 (95% CI: 0.70-0.95) and 0.43 (95% CI: 0.21-0.69). There was a high degree of heterogeneity between studies reporting on endoanal ultrasound sensitivity (df = 3, I = 92%).
  
  
  CONCLUSIONS
  From the available literature, the summarized performance characteristics for MRI and endoanal ultrasound demonstrate comparable sensitivities at detecting perianal fistulas, although the specificity for MRI was higher than that for endoanal ultrasound. Both specificity values are considered to be diagnostically poor, however. The high degree of data heterogeneity and the shortage of applicable studies precludes any firm conclusions being made for clinical practice. Future trials with improved study design (including prospective data collection and consideration of verification bias) may help to further clarify the role of MRI in the assessment and treatment response monitoring of perianal fistulas (particularly in patients with Crohn's disease).
authors.affiliation: St. Mark's Institute, Harrow, United Kingdom. md0u812a@mac.com
authors.forename: Muhammed R S
authors.initials: MR
authors.lastname: Siddiqui
authors.forename: Hutan
authors.initials: H
authors.lastname: Ashrafian
authors.forename: Phil
authors.initials: P
authors.lastname: Tozer
authors.forename: Najib
authors.initials: N
authors.lastname: Daulatzai
authors.forename: David
authors.initials: D
authors.lastname: Burling
authors.forename: Ailsa
authors.initials: A
authors.lastname: Hart
authors.forename: Thanos
authors.initials: T
authors.lastname: Athanasiou
authors.forename: Robin K
authors.initials: RK
authors.lastname: Phillips
mesh_terms: D001003:Anal Canal / Q000000981:diagnostic imaging / Q000473:pathology; D003424:Crohn Disease / Q000150:complications / Q000175:diagnosis; D003937:Diagnosis, Differential; D019160:Endosonography / Q000592:standards*; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional / Q000592:standards*; D012003:Rectal Fistula / Q000175:diagnosis* / Q000209:etiology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity