HTayar i ADaghfou s FJabnoun KBouzaid i LRezgui Marhou l Radiology services Trauma center Tunisia Taher Maamouris Hospita l Nabeul GI27 INTRODUCTION ID: 284436
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Slide1
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*lRadiology servicesTrauma center*, TunisiaTaher Maamouri’s Hospita**l, Nabeul
GI27Slide2
INTRODUCTION
Anal fistula is a benign condition but may cause considerable distress to the patient and difficulty for the surgeon. Fistulae are
intimately
related
to the anal sphincter
complex
,
so
that
incision and drainage
may
damage
these
muscles to
avariable
degree
with
the
risk
of anal incontinence.
The correct balance
between
eradication
of infection and maintenance of continence
depends
upon
accurate
pre
-
operative
assessment
of
fistula
geography
,
namely
the site and
level
of
any
internal
opening
, the
anatomy
of the
primary
track
and the
presence
of
any
secondary
ramifications.
These
questions are best
answered
by MRI,
which
is
more
accurate
than
all
other
pre
-
operative
investigations. Slide3
OBJECTIVES
Illustrate the contribution of magnetic resonnance imaging in the diagnosis and assessement of anal fistulas for providing valuable
assisstance
in
conducting
surgical
.Slide4
MATERIALS AND METHODSRetrospective
study.The study population comprised teen adult patients complaining of anal fistula and whose
all
received
a
clinical
examination
by a surgeon and a
pelvic
MRI.
The
protocol
includes
T1 and T2
weighted
sequences
in
three
planes, a
sequence
of diffusion and T1 Fat
Sat
gadolinuim
injection in
three
planes.Slide5
resultsAverage
age: 38 years.Sex ratio: 6 men/4women.All patients were followed for crohn’s disease.
Pelvic
MRI has
objectified
6
complex
fistula
and 4 cases of simple
fistula
.
Collections
were
observed
in 5 cases.Slide6
Results : EXAMPLE 1
ab Simple linear
intersphincteric
fistula
.
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 same region, representing inflammation ( ).
cSlide7
RESULTS: EXAMPLE 2:
Complex
intersphincteric
fistula
with
horseshoe
track
.
43-year-old man with complex
fistulating
Crohn’s disease. The intersphincteric fistulous track ( in axial T2 Weighter”
a”and
STIR”b” images)
crosses the midline in the anterior interhemispheric
space ( in coronal T2-Weighter images
“c”) forming a horse-shoe track.
a
b
cSlide8
RESULTS: EXAMPLE 2 :
defEnhancement
on
contrast
administration
is
noted
in the
three
plans axial
(d)
, coronal
(e)
et sagittal
(f)
T1-weighted postcontrast images ( ):ACTIVE FISTULASlide9
RESULTS: EXAMPLE 3 :
acbSimple
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. ( )Slide10
RESULTS : EXAMPLE 4:
abc
Trans
-
sphincteric
complex
fistula
with
abscess
There are axial T2-Weighted images:
The trans-
sphincteric
track is seen entering the anal canal at 6 o’ clock ( ).In addition, an abscess in the left ischioanal
fossa
is seen
( ).Slide11
RESULTS : EXAMPLE 4:
defAxial 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
.Slide12
RESULTS : EXAMPLE 5:
Complex fistula and voluminous abcesses(a) Axial T2-weighted image shows large abscess extending into right gluteus and levator ani 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.
a
b
cSlide13
RESULTS : EXAMPLE 5:(d)
Coronal sequence shows the course of the fistula ( )from the canal anal to the left levator ani muscle .dSlide14
dISCUSSION
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. Slide15
dISCUSSIONMRI 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. Slide16
dISCUSSIONT2W 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.Slide17
dISCUSSIONThe 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. Slide18
dISCUSSIONMRI 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 fistula2 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 ischiorectal fossa5 Supralevator and translevator diseaseSlide19
CONCLUSION
Magnetic resonance imaging 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.