1. Fistulising Crohn’s desease
BEN ROMDHANE M H
Hopital Avicenne Bobigny France

2. Fistulas : serious complication of CD
High morbidity and mortality
Life time risk for developing a fistula in patients with CD: between 20% and 40%
Perianal CD in 5–25% of CD, may be the presenting symptom of CD
fistulas : one of episodic exacerbation frequently multiple, complex, recurrent
Associated with active CD in small bowel (one-third) or colon( half) of the patients

3. goals that impact patient management:
- defining fistula anatomy
- Identifying underlying etiology
Current imaging of fistulas include:
barium fistulography
small bowel fluoroscopic enteroclysis
abdomino-pelvic CT
CT and MR enterography (CTE and MRE)
pelvic MRI ( for perianal fistulas)

4. CTE exploits the high spatial resolution and speed of multidetector CT
MRI exploits the high contrast resolution
CTE and MRE using large volumes of neutral oral contrast agents
to generate exquisite images of the small bowel wall, lumen, and mesentery.

5. New imaging advantages over barium studies
No superimposition of bowel loops
No require filling of the fistulous tract
fistulas typically involve:
perienteric mesentery
retroperitoneal space
abdominal wall musculature
Sinus tracts and abscesses can be readily
characterized

6. Appearance of Crohn’s fistulas
81% appeared as extraenteric tracts.
86% were hyperenhancing compared to adjacent bowel loops
hyperenhancement reflects inflammation in the fistulous tract
most arose from actively inflamed large or small bowel
14% fistulas were isoenhancing, with half of these being perianal fistulas

10. Enteroenteric and enterocutaneous fistulas
No air or fluid was seen in 68% fistulas
Larger fistulas tracts filled with fluid
86% of enteroenteric fistulas and (25%) of enterocutaneous fistulas arose from a bowel segment with signs of active CD
CT E able to detect patients with fistulas with an accuracy of 94%

15. Perianal fistulas usually hyperenhancing extraenteric tracts
some perianal and enterovesical fistulas without hyperenhancement perhaps reflecting chronicity
contain air 27% fluid 27%
Some associated with perianal abscesses
Rectovaginal fistula poorly demonstrated at CT
MR examination preferred

18. Enterovesical and enterovaginal fistulas
direct fistula tract observed in some cases
or detected by secondary inflammatory signs:
- thickened bladder or vaginal wall
- small air intravesical or intramural at the site
of fistula insertion in the bladder or vagina

22. Abscesses fluid collections with hyperenhancing rims
multiple locations:
interloop / mesenteric
perianal / perirectal
subcutaneous abdominal wall
retroperitoneal
69% appeared to connect to bowel
89% of these bowel segments demonstrate CT findings of active inflammation

29. 20% of CD demonstrate penetrating CD at CTE
Clinical signs and symptoms protean and do not predict penetrating disease :
CTE particularly beneficial
No clinical suspicion in half cases with fistulas and abscess prior to CTE
In those patients CRP normal in 35% of cases
61% underwent a change in medical therapy (initiation or dose escalation) following detection of penetrating CD on CTE
18% underwent surgical or percutaneous radiologic intervention following CTE

30. Treatment for fistulizing CD depends upon symptoms and occasionally the site and extent
Radiologists should:
- identify fistula , describe its location (by its
proximal and distal connections), its extent
(number of tracts)
- identify and localize abscesses, enteric
involvement by inflammatory
- other superimposed conditions important in
guiding appropriate management decisions

31. Complications should also be described
abscess formation, small bowel obstruction
location proximal to a stricture
which may help predict the efficacy of medical
or surgical management
many enteroenteric, perianal F can be treated
successfully with modern medical therapies
enterovesical and enterovaginal fistulas often
require surgical treatment

32. Refinements in the surgical approach to perianal complications have led to the concept of sphincter-saving procedures
Need exact preoperative diagnosis
In known or suspected PCD, diagnostic efforts focused on defining type, location and nature of perianal involvement

33. protocol Axial and coronal Axial proton density and T2
Coronal T1 spin-echo (SE) or fast spin echo
with and without fat suppression
Axial , coronal T1 gado fat sat

34. Although anal canal runs obliquely coronal nonangulated images adequate to diagnose
because perianal complications spread commonly dorsal to the subcutaneous tissue
More important to cover the subcutaneous tissue overlying the gluteus maximus muscle with coronal images than all parts of ventral abdominal wall

35. levator ani muscle separates supralevatoric from infralevatoric space
some overlap exists between different compartments of the infralevatoric space
divided into ischiorectal fossa, para-anal space, and subcutaneous space

36. Surgical approach depends on location of perianal abscess
- intersphincteric abscess is drained into
the anal canal
- ischiorectal abscess requires a
transcutaneous approach

37. Schematic representation of the four types of perianal fistulas as classified by Parks et al.
Essary B . Pediatr Radiol (2007)

38. Surgical terminology
Best communication with use of a common language between the referring physician and the radiologist
Because perianal complications of CD were being diagnosed and treated long before MR imaging
keeping the well-established surgical terminology (Parks’ classification )

39. Anatomic classification of perianal fistulas

46. In contrast to active disease, scar tissue hypointense on T1, proton density, and T2
With the use of fat suppression increased signal intensity may also be seen in scar tissue, most likely at the beginning of the healing process
Same topographic approach to the different anatomic types of fistulas, and abscesses

47. High accuracy of MRI in separating active from inactive perianal complications:
- scar tissue markedly hypointense( T1,pd,T2)
- active CD hyperintense ( T2 , pd) gadolinium enhancement
Combination of the two pulse sequences precludes mistaking hyperintense fatty tissue or bright signals of small blood vessels for collections
If only fat-sat sequences used to differentiate scars from active CD,false positive might occur because scar can be slightly hyperintense

48. Coronal and transverse MRI show well the location of collections witch help surgeon to plan the intervention
Differentiation between perianal abscess and fistula can be important in therapeutic decision
Surgical drainage mandatory for symptomatic patient with perianal abscess
Less aggressive treatment for isolated fistula
MRI less sensitive in ano-vaginal fistula

49. limitation of CT identifying and classifying fistulas and differentiation between active fistulas and scar
MRI accuracy in detection of perianal abscesses is almost 100%
MRI prefered to CT when available
(radiation dose ;young patient)
Anal endosonography sensitive method in perianal CD With 10-MHz probes but necessity for general anesthesia, operator dependant

50. Conclusion 1 CTE detect clinically occult fistulizing C D
Detection results in changes in patient management in the majority of cases
Fistulas generally hyperenhancing, extraenteric tracts
often without internal air or fluid
abscesses, sinus tracts are often seen connecting to inflamed bowel loops

51. Conclusion 2 MRI reliable method for perianal CD:
- detecting perianal abscesses and fistulas
- classifying these complications according to the surgical terminology
- guiding minimally invasive interventional procedures.
Common language for radiologists and surgeons permits the greatest benefit for patients with perianal complications of CD