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Abdominal imaging ano fistula jm tubiana

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  • 1. MRI of fistula in ano C HOEFFEL JM TUBIANA
  • 2. Objectives •  Describe the impact of MRI in the management of fistulas •  Propose protocols and report forms used for fistula in ano evaluation
  • 3. Fistula in ano •  Track communicating with the rectum or the anal canal via an internal opening and generally with an external opening •  Infection of an intersphincteric glandfollowed by drainage of the abscess in every directions
  • 4. WHY MRI ? •  MRI versus clinical examination versus endoanal ultrasound –  104 patients evaluated with the three modalities and follow-up (MRI or surgery) as the gold standard. •  MRI versus Clinical examination –  Correct classification 90 vs 61 % –  Best for detection of abscesses, of horseshoe fistulas Buchanan Radiology 2004
  • 5. WHY MRI ? •  MRI versus endoanal ultrasonography –  Internal opening 97 vs 91 % –  Best detection of complex tracts and abscesses with MRI Buchanan Radiology 2004
  • 6. WHY and WHEN MRI ? •  First suspicion of fistula –  30 patients with pre-operative MRI, surgery and rectal exam under GA + follow-up with surgery and 12 months MRI. Disagreement n=15 • Minor disagreement , n=12 • Change in management, n=3 • MRI ‘s impact on treatment decisions = 10 % Buchanan Br J Surg 2003
  • 7. WHY and WHEN MRI ? •  Recurrent Fistula 71 patients –  Agreement surgery/MRI, n=40 • 5 with recurrent fistulas –  Discrepancies surgery/ MRI, n=31 • 16 with recurrent fistula (52 %), p=0.0005, at the location predicted by MRI • MRI guided surgery decreases recurrence rate down to 75 %. Buchanan Lancet 2002
  • 8. WHY and WHEN MRI ? •  Endoscopic Ultrasonography –  Particularly for intersphincteric fistulas –  Less accurate in case of sepsis or complex fistulas •  MRI –  First-step examination in case of recurrent fistula –  If presence of a complex fistula at US or clinical examination –  Before anti-TNF treatment Williams Dis Colon Rectum 2007
  • 9. MRI : HOW ? •  Technique •  Anatomy •  Classification
  • 10. MRI Technique •  Sequence Selection •  Planes •  Slices orientation
  • 11. MRI Technique •  1.5 Tesla ou 3 T •  Phased-array coil, without any preparation nor endorectal probe.
  • 12. Sequences –  Anatomical views Sag T2 - Ax T2 Pelvis –  Fistula imaging • STIR • Fat Suppressed T2 • Gado Fat suppressed T1 3 DT2 w-TSE with post processing reformation ?
  • 13. How to choose sequences ? •  T2 FS / STIR –  Simple –  No injection –  High signal intensity of the inflammatory tract –  Fibrous areas low signal intensity –  Less sensitive for very thin tracts –  Difficult to differentiate inflammation from fluid HALLIGAN Radiology 2006 Before tt STIR After tt STIR
  • 14. Sequences: How to choose? •  T1 Gado FS –  Injection –  Inflammatory tract white –  Fibrosis/Fluid black –  May overinterpret a healing fistula T1 Gado FS
  • 15. STIR vs T1 Gado FS •  STIR versus T1 Gado FS Gado FS –  Overinterpretation of enhancement with gado, while no fluid on STIR, when a fistula is on its way to heal B0 STIR
  • 16. STIR vs T1 Gado FS Differentiate granulation tissue from fluid Before anti TNF treatment Gado FS STIR Abscess? Granulation tissue? No abscess
  • 17. STIR vs T1 Gado FS STIR Gado FS Abscess
  • 18. Sequences: How to choose? •  Combined T1 Gado FS + STIR •  Role of DW MRI? T1 gado FS Axial STIR Axial diff b500
  • 19. T2 Ax T1 Gado FS Fusion diff-T2 Fusion diff-T2
  • 20. MRI Technique •  Slice thickness –  3-4 mm •  Section Planes –  Axial - relationship to sphincters –  Coronal - level of internal opening and relationship to levator ani muscles. –  Sagittal may be useful (anovaginal fistula)
  • 21. MRI Technique- Slice positioning Important to assess the level of internal opening with regard to puborectal muscle and better evaluation of relationship/ levator ani
  • 22. MRI Technique •  FOV – not just anal canal –  In some cases must cover perineum, presacral space, supralevatorian space
  • 23. Anatomy External Sphincter-T2 •  Prolongs puborectal muscle •  Striated muscle •  Circular •  Hyposignal 2 cm
  • 24. Anatomy Internal Sphincter- T2/ STIR •  Prolongs rectal muscular layer •  Smooth muscle •  Circular •  Intermediate to high signal
  • 25. GADO FS
  • 26. Classification •  Why is it important? ü Aims of surgery o  Continence preservation o  Infectious foci and secondary tracts elimination ü Surgical Options o  Seton tight or not o  FistulotomyFistulectomy o  Intersphincteric amputation, Flap
  • 27. o  Fistulotomy-Fistulectomy Pr Halligan
  • 28. Intersphincteric amputation
  • 29. Superficial Fistula Horsthuis AJR 2004 T2
  • 30. Intersphincteric Fistula Involvement of internal sphincter No risk for continence Horsthuis AJR 2004
  • 31. Transphincteric Fistula Involvement of both internal and external sphincters External sphicter section threatens continence Ax gado FS
  • 32. Transphincteric Fistula •  Sometimes internal opening less obvious but predictable, located at the penetrating point of the external sphincter or at the epicenter of the intersphincteric sepsis.
  • 33. Suprasphincteric Fistula 20 % Rare, upwards and crosses the levator ani muscle. Its section may threaten continence. Often inaccurately classified
  • 34. Extrasphincteric Fistula= primitive rectal disease (CD, cancer, diverticulitis)
  • 35. Ax Gado FS
  • 36. Complications •  Abscess
  • 37. Complications Dr Damian Tolan, Leeds
  • 38. Report 1.Fistula type - simple, complex, anovaginal, horseshoe
  • 39. Ax T2 fusion Coro gado FS Ax gado FS
  • 40. Report 1.Fistula Type 2. Internal opening Level and position (clockwise)
  • 41. Report 1.Fistula type 2. Internal opening Level and position (clockwise) 3. Primary fistula pathway to the external opening Location and hour
  • 42. Report 1.Fistula type 2. Internal opening Level and position (clockwise) 3. Primary fistula pathway to the external opening Location and hour
  • 43. Report 1.Fistula type 2. Internal opening Level and position (clockwise) 3. Primary fistula pathway to the external opening Location and hour 4. Number and position of supralevatorian extensions?
  • 44. Report 1.Fistula type 2. Internal opening Level and position (clockwise) 3. Primary fistula pathway to the external opening Location and hour 4. Number and position of supralevatorian extensions? 5. Number and positions of collections
  • 45. Report •  Activity Criteria – Hypersignal T2 – Enhancement
  • 46. Ax gado FS T2 Stir B0 B1000
  • 47. Report •  Sphincter •  Rectum T1 FS Gado
  • 48. •  Main anatomic criteria –  Fistula type •  •  •  •  Simple Complex Horseshoe Ano-vaginal –  Relationship with levator ani muscle •  Inflammation criteria –  Fistula •  Hypersignal T2 •  Enhancemnet –  Abscess –  Rectal wall –  Parks’classification •  •  •  •  Intersphincteric Transsphincteric Suprasphincteric Extrasphincteric –  Openings •  Others –  Presence of a seton –  Distant extension –  Sphincteric ring abnormalities (rupture…)