2IntroductionPre-operative confirmation of fistula complexity has been shown to facilitate surgical planning of sphincter saving techniques and to reduce the incidence of unidentified sepsis, which is the leading cause of fistula recurrence .
3Imaging ObjectivesDetermine relationship of fistula to sphincter complexIdentify any secondary fistulous tracks
4Imaging Modalities Fistulography Endoanal ultrasound Magnetic resonance
5Fistulography Acute tracks may not have a patent lumen Difficult to relate the track to the sphincter and levator aniShown to be accurate in only 16% Helpful for chronic fistulae with an external opening distant from the anus
6Endoanal ultrasound Operator dependent Highly accurate at identifying the internal opening Depicts fewer secondary extensions than MRDifficulty differentiating active track from fibrosis
7Magnetic ResonanceMost accurate technique for evaluation of the primary track and any extensions .More accurate predictor of patient outcome than surgical findings at EUA.
8Prospective study 56 patients Beets-Tan RGH, Beets GL, Gerritsen van der Hoop A. et al. Preoperative MR Imaging of Anal Fistulas: Does it Really Help the Surgeon? Radiology 2001; 218:75-84Prospective study 56 patientsMR prior to surgery but result witheld from surgeon until end of surgery while patient still anaesthetisedImportant additional information in 21%. Benefit greatest in crohns (40%), recurrent fistulas (24%), primary fistulas (8%)
9Prospective study 48 patients Spencer JA, Chapple K, Wilson D et al. Outcome After Surgery for Perianal Fistula: Predictive Value of MR Imaging. AJR 1998; 171:Prospective study 48 patientsMR and then surgical exploration blinded to MRMR categorised 41% complex. Surgery 38%. Only agreed in 8 cases19 patients required further surgery. 13 of these considered complex on MR, 9 by surgeryMR better at predicting outcome than surgery
10Gadolinium? Post operative problems Complex cases such as crohns disease
11Endoanal coil?Endocoils give superior anatomical resolution of fistula disease within the sphincterResolution falls off rapidly outside the sphincterComplex tracks outside the sphincter are not well seen
28DiscussionMajority (50%) of patients with idiopathic peri-anal fistulation have uncomplicated disease25% have trans-sphincteric fistulae complicated by secondary tracks or ischiorectal abscessSupra-levator or trans-levator disease is relatively rare in this patient group (8%).
86SummaryMR is a valuable modality in the assessment of peri-anal fistulaAccurately identifies disease complexity
87References1: Beets-Tan RGH, Beets GL, Gerritsen van der Hoop A. et al. Preoperative MR Imaging of Anal Fistulas: Does it Really Help the Surgeon? Radiology 2001; 218:75-842: Bartram C, Buchanan G. Imaging anal fistula. Radiol Clin N Am 41 (2003)3: Kuijpers HC, Schulpern T. Fistulography for fistula-in-ano: is it useful? Dis Colon Rectum 1985;28:103-44: Buchanan GN, Halligan S, Bartram CI et al. Clinical Examination, Endosonography, and MR Imaging in Preoperative Assessment of Fistula in Ano: Comparison with Outcome-based Reference Standard. Radiology 2004; 233:5: Spencer JA, Chapple K, Wilson D et al. Outcome After Surgery for Perianal Fistula: Predictive Value of MR Imaging. AJR 1998; 171:6: Horsthius K, Stoker J. MRI of perianal crohn’s disease. AJR 2004; 183:7: Morris J, Spencer JA, Ambrose S. MR Imaging Classification of Perianal Fistulas and Its implications for Patient Management. Radiographics 2000; 20: