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MR Imaging of fistula : Its inputs and implications for surgical management

H.Tayar *i, A.Daghfou *s, F.Jabnoun **, K.Bouzaid **i, L.Rezgui Marhou *l Radiology services Trauma center*, Tunisia Taher Maamouri’s Hospita **l, Nabeul. MR Imaging of fistula : Its inputs and implications for surgical management. GI27.

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MR Imaging of fistula : Its inputs and implications for surgical management

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  1. H.Tayar*i, A.Daghfou*s, F.Jabnoun**, K.Bouzaid**i, L.RezguiMarhou*l Radiology services Trauma center*, Tunisia TaherMaamouri’sHospita**l, Nabeul MR Imaging of fistula : Its inputs and implications for surgical management GI27

  2. Anal fistulais a benign condition but may cause considerabledistress to the patient and difficulty for the surgeon. Fistulae are intimatelyrelated to the anal sphincter complex, sothat incision and drainage may damage these muscles to avariabledegreewith the risk of anal incontinence. The correct balance betweeneradication of infection and maintenance of continence dependsuponaccuratepre-operativeassessment of fistulageography, namely the site and level of anyinternalopening, the anatomy of the primarytrack and the presence of anysecondary ramifications. These questions are best answered by MRI, whichis more accuratethan all otherpre-operative investigations. INTRODUCTION

  3. Illustrate the contribution of magneticresonnanceimaging in the diagnosis and assessement of anal fistulas for providingvaluableassisstance in conductingsurgical. OBJECTIVES

  4. Retrospectivestudy. The study population comprisedteenadult patients complaining of anal fistula and whose all received a clinicalexamination by a surgeon and a pelvic MRI. The protocolincludes T1 and T2 weightedsequences in three planes, a sequence of diffusion and T1 Fat Satgadolinuim injection in three planes. MATERIALS AND METHODS

  5. Averageage: 38 years. Sex ratio: 6 men/4women. All patients werefollowed for crohn’sdisease. Pelvic MRI has objectified 6 complexfistula and 4 cases of simple fistula. Collections wereobserved in 5 cases. results

  6. Results : EXAMPLE 1 b c a Simple linearintersphinctericfistula. Axial T2-weighted (a) and STIR images (b) show fistulous tracks in the intersphincteric plane ( ). Coronal T1-weighted postcontrast image at the same level (c) demonstrates hyperenhancement in the sameregion, representing inflammation ( ).

  7. RESULTS: EXAMPLE 2: b c a Complexintersphinctericfistulawithhorseshoetrack. 43-year-old man with complex fistulatingCrohn’sdisease. The intersphinctericfistuloustrack ( in axial T2 Weighter”a”andSTIR”b” images) crosses the midline in the anterior interhemispheric space ( in coronal T2-Weighter images“c”) forming a horse-shoe track.

  8. RESULTS: EXAMPLE 2 : d e f Enhancement on contrast administration isnoted in the three plans axial (d), coronal (e) et sagittal (f) T1-weighted postcontrast images ( ): ACTIVE FISTULA

  9. RESULTS: EXAMPLE 3 : a b Simple transphincteric fistula 29-year-old woman with long-standing Crohn’s disease. (a) STIR image showing a transsphincteric fistula. ( ) (b) Axial and ( c) coronal Sagittal T1-weighted postcontrast images in the same patient demonstrates hyperenhancement along fistulous tract. ( ) c

  10. RESULTS : EXAMPLE 4: c a b Trans-sphinctericcomplexfistulawithabscess There are axial T2-Weighted images: The trans-sphincteric track is seen entering the anal canal at 6 o’ clock ( ). In addition, an abscessin the left ischioanalfossaisseen ( ).

  11. RESULTS : EXAMPLE 4: d e Axial T1-weighted postcontrast image (d) in the same patient demonstrates hyperenhancement along a contiguous fistulous tract to the skin ( ). Axial and coronal T1-weighted postcontrast images (e-f) shows partial enhancement of rim ( ), indicating presence of fluid in center with rim of inflammatory tissue: abcesses. f

  12. RESULTS : EXAMPLE 5: a b c Complex fistula and voluminous abcesses (a) Axial T2-weighted image shows large abscess extending into right gluteus and levatorani muscles.( ) (b) Axial fat-saturated T2-weighted image shows abscess (a) more clearly because bright signal of fat, in which abscess is located, is suppressed. ( ) (c ) T1-weighted image after administration of IV contrast medium clearly shows rim enhancement of lesions on right ( ), indicating presence of large amount of pus.

  13. RESULTS : EXAMPLE 5: (d) Coronal sequence shows the course of the fistula ( ) from the canal anal to the left levatorani muscle . d

  14. Anal fistula is a common disease that has long challenged surgeons’ skills. Perianal fistula, if not treated properly will result in one of two terrible complications, recurrence or incontinence. The key to successful management of fistula-in-ano lies in correctly identifying the full extent of disease and its relationship to the sphincter complex. It’s the role of Magnetic Resonnance Imaging. This exam is more sensitive than even surgical exploration of the tract. dISCUSSION

  15. MRI imaging of perianal fistulae relies on the inherent high soft tissue contrast resolution and the multiplanar display of anatomy by this modality. It’s especially useful in patients with fistulae associated with Crohn’s disease and those with reccurent fistulae, as these entities are associated with branching fistulous tracts. Missed extensions are the commonest cause of recurrence. dISCUSSION

  16. T2W images (TSE and fat-suppressed) provide good contrast between the hyperintense fluid in the tract and the hypointense fibrous wall of the fistula, while providing good delineation of the layers of the anal sphincter. Gadolinuim-enhanced T1W images are useful to differentiate a fluid-filled tract from an area of inflammation. The tract wall enhances, whereas the central portion is hypointense. Abscesses are also very well depicted on post-gadolinuim images. dISCUSSION

  17. The exact location of the primary tract (ischioanal or intersphincteric) is most easily visualized on axial images. The presence of disruption of the external anal sphincter differenciates a transsphincteric fistula from an intersphincteric one. The internal opening of the fistula is also best seen in this plane. Coronal images depict the levator plane, thereby allowing differentiation of supralevator from infralevator infection. A combination of an axial and a longitudinal series (coronal, sagittal or radial) will provide all the necessary details. dISCUSSION

  18. MRI also allows to classify anal fistulas in five grades according to: JAMES’S UNIVERSITY HOSPITAL MR IMAGING CLASSIFICATION OF PERIANAL FISTULAS Grade Description 0 Normal appearance 1 Simple linear intersphincteric fistula 2 Intersphincteric fistula with intersphincteric abscess or secondary fistulous track 3 Trans-sphincteric fistula 4 Trans-sphincteric fistula with abscess or secondary track within the ischioanal or ischiorectalfossa 5 Supralevator and translevator disease dISCUSSION

  19. Magneticresonanceimaging has become a powerful tool in the evaluation of anal anatomy. In patients with complex disease, MRI is an important adjunct in delineating disease location and extent, its relationship to sphincter muscles, and in planning management. MRI also plays an important role in evaluating the response to medical and surgical therapies. CONCLUSION

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