Presentation is loading. Please wait.

Presentation is loading. Please wait.

MRI imaging of Perianal fistula

Similar presentations

Presentation on theme: "MRI imaging of Perianal fistula"— Presentation transcript:

1 MRI imaging of Perianal fistula
Dr. Ahmed Refaey , FRCR Consultant Radiologist Riyadh Military Hospital

2 Format of the lecture Anatomy Pathogenesis Imaging techniques
Scanning protocoles Classification Examples

3 Anatomy

4 Anatomy Anatomical canal :
- extends from perineal skin to dentate line Surgical canal : - extends from perineal skin to anorectal ring ( 1-1.5cm abov e dentate line ) - total length 4-5 cm

5 Anal sphincter comprised of 3 layers Internal sphincter
- continuance of circular smooth muscle of rectum, involuntary, contracts at rest & relaxes at defecation Intersphincteric space External sphincter - voluntary striated muscle , continuous cranially with puborectal muscle &levator ani


7 Puborectal muscle has its origin on both sides of the symphysis pubis, forming a sling around the anorectum

8 The puborectal muscle is contracted at rest and accounts for the 8O0 angulation of the anorectal junction . It relaxes during defecation

9 On axial and coronal MR images , the different layers of anal sphincter and the surrounding structures can be displayed perfectly

10 Coronal Axial

11 pathogenesis

12 Perianal fistula Abnormal connection between the epithilialised surface of the anal canal and the skin.

13 Causes 1ry - obstruction of anal gland which leads to stasis & infection with abscess & fistula formation ( most common cause ) 2ry - iatrogenic ( post hemorrhoiedal surgury ) - inflammatory bowel dis. ( crohn’s disease ) - infections ( viral , fungal or TB ) - malignancy


15 Imaging techniques

16 Imaging techniques Fistulography Endosonography CT MRI

17 Perianal fistulography

18 Anal endosonography

19 CT

20 MRI protocol T1W &T2W fse axial and coronal T2W with fat sat T1W + CM
FOV 200

21 T2W  anatomy T2W with fat sat ---- fistula

22 The anal clock P: anterior perineum n: natal cleft

23 The anal clock The surgeon’s view of the perianal region when the patient is in the supine lithotomy position , corresponds to the orientation of axial MRI of the perianal region

24 Reporting Position of the mucosal opening on axial images using anal clock Distance of mucosal defect to perianal skin on coronal images 2ry fistulas or abscess

25 classification

26 Classification Parks classification 1- intersphincteric
2- transsphincteric 3- extrasphincterisc 4-suprasphincteric Intersphincteric & transsphincteric are the most common Intersphincteric --> 70 % Transsphincteric -->20%

27 St. James university hospital classification
MR imaging Grading of perianal fistulas

28 MRI Grading of perianal fistulas
Grade 1 : simple linear intersphincteric fistula Grade 2 : intersphincteric fistula with abscess or 2ry track Grade 3 : transsphincteric fistula Grade 4: transsphinteric fistula with abscess or2ry track within ischeorectal fossa Grade 5 : supralevator & translevator fistula

29 Grade 1 : simple linear intersphincteric fistula



32 Intersphincteric fistula
Axial T2W with and without fat saturation The intersphincteric fistula located at 6 o’clock

33 Intersphincteric fistula

34 Perianal fistula with an abscess

35 Grade 2 : intersphincteric fistula with abscess or 2ry track

36 Grade 3 : transspincteric fistula


38 Transsphincteric fistula
The defect through internal & external sphincter at 6 o’clock is clearly visible

39 Transsphincteric fistula at 11 o’clock

40 Grade 4: transsphinteric fistula with abscess or2ry track within ischeorectal fossa



43 Grade 5 : supralevator & translevator fistula

44 Suprasphincteric fistula
Two tracts in ischeorectal region The right sided tract runs over the puborectal muscle (asterisc) & the mucosal opening lies at the level of dentate line (black arrow)

45 Extrasphincteric fistula
A small abscess in left ischeoanal fossa , the fistula runs through levator ani , it is therefore above the sphincter complex and extrasphincteric

46 Complex fistula 2 tracts in left buttock form single tract
The fistula breaks through the external sphincter In intersphincteric space it divides again into 2 tracts One ends blindly in the intersphincteric space The other breaks through the internal sphincter with mucosal defect at 1 o’clock

47 Differential diagnosis

48 Pielonidal sinus Small abscess just above the nates
No relation with sphincter complex

49 Proctitis No fistula was seen
Diffuse thickening of rectal mucosa due to proctitis

50 Ischiorectal space abscess
An abscess in ischiorectal space with no connection to the sphincter complex

51 references

52 Goodsall DH, Miles WE. Diseases of the anus and rectum
Goodsall DH, Miles WE. Diseases of the anus and rectum. London, England: Longmans, Green, 1900. ↵ Parks AG, Gordon PH, Hardcastle JD. A classification of fistula-in-ano. Br J Surg 1976; 63:1-12. ↵ Halligan S. Imaging fistula-in-ano. Clin Radiol 1998; 53: ↵ Kuijpers HC, Schulpen T. Fistulography for fistula-in-ano: is it useful? Dis Colon Rectum 1985; 28: ↵ Weisman RI, Orsay CP, Pearl RK, et al. The role of fistulography in fistula-in-ano: report of 5 cases. Dis Colon Rectum 1991; 34: ↵ Choen S, Burnett S, Bartram CI, Nicholls RJ. Comparison between anal endosonography and digital examination in the evaluation of anal fistulae. Br J Surg 1991; 78:

53 ↵ Guillaumin E, Jeffrey RB, Shea WJ, et al
↵ Guillaumin E, Jeffrey RB, Shea WJ, et al. Perirectal inflammatory disease: CT findings. Radiology 1986; 161: ↵ Yousem DM, Fishman EK, Jones B. Crohn disease: perirectal and perianal findings at CT. Radiology 1988; 167: ↵ Barker PG, Lunniss PJ, Armstrong P, Reznek RH, Cottam K, Phillips RK. Magnetic resonance imaging of fistula-in-ano: technique, interpretation, and accuracy. Clin Radiol 1994; 49:7-13. ↵ Spencer JA, Ward J, Beckingham IJ, Adams C, Ambrose NS. Dynamic contrast-enhanced MR imaging of perianal fistulas. AJR Am J Roentgenol 1996; 167: ↵ Haggett PJ, Moore NM, Shearman JD, Travis SPL, Jewell DP, Mortensen NJ. Pelvic and perianal complications of Crohn's disease: assessment using magnetic resonance imaging. Gut 1995; 36:

54 Koelbel G, Schmeidl U, Majer MC, et al
Koelbel G, Schmeidl U, Majer MC, et al. Diagnosis of fistulae and sinus tracts in patients with Crohn's disease: value of MR imaging. AJR Am J Roentgenol 1989; 152: Myhr GE, Myrvold HE, Nilsen G, Thoresen JE, Rinck PA. Perianal fistulas: use of MR imaging for diagnosis. Radiology 1994; 191: ↵ Hussain SM, Stoker J, Schouten WR, Hop WCJ, Lameris JS. Fistula-in- ano: endoanal sonography versus endoanal MR imaging in classification. Radiology 1996; 200: ↵ Halligan S, Bartram CI. MR imaging of fistula-in-ano: are endoanal coils the gold standard? AJR Am J Roentgenol 1998; 171: ↵ Spencer JA, Chapple K, Wilson D, Ward J, Windsor ACJ, Ambrose NS. Outcome after surgery for perianal fistula: predictive value of MR imaging. AJR Am J Roentgenol 1998;

55 Thank you

Download ppt "MRI imaging of Perianal fistula"

Similar presentations

Ads by Google