Anal perianal imaging part 2 perianal fistula ct mri dr ahmed esawy Anal perianal imaging part 1 ct mri anatomy dr ahmed esawy ANAL ,PERIANAL IMAGING (endovaginal ultrasound endoanal ultrasound perineal ultrasound MRI) FOR ANAL ,PERIANAL DISEASE3/ Image reconstruction and processing artifacts • ANAL ANATOMY • ANAL PERIANAL FISTULA • ANAL TEARS (OBSTETRIC) • FAECAL INCONTINENCE • OTHER DISEASES • NATOMY ANORECTAL ANATOMY : • Anal Sphincter: • internal sphincter • external sphincter • Puborectalis muscle and levator ani • Sub cutaneous perianal fistula • Sub mucous perianal fistula • Low anal perianal fistula • High anal perianal fistula • Pelvi rectal perianal fistula • Simple fistulography • Perianal fistulography • Endosonography Perianal fistula • A. A superficial fistula. • B. An intersphincteric fistula. • C. A transsphincteric fistula. • D. A suprasphincteric fistula. • E. An extrasphincteric fistula. •

1. Dr Ahmed Esawy
ANAL PERIANAL IMAGING
Dr. Ahmed Esawy
MBBS M.Sc MD

2. Dr Ahmed Esawyyour name
ANAL ,PERIANAL IMAGING
(endovaginal ultrasound
endoanal ultrasound
perineal ultrasound
MRI)
FOR ANAL ,PERIANAL
DISEASE

3. Dr Ahmed Esawy
PERIANAL
FISTULA
IMAGING

4. Dr Ahmed Esawy
FISTULA:
 ABNORMAL communication between lumen of one
viscus and lumen of another NTERNAL FISTULA)
(or)
between lumen of one hollow viscus to the exterior
(EXTERNAL FISTULA)
(or)
between any two vessels

5. Dr Ahmed Esawy
Latin : flute (or) a pipe (or) a tube.

6. Dr Ahmed Esawy
• Anal fistula, is a single track with an external opening and an
internal opening in the mucosa of the anal canal or rectum.
• However the track usually has a complicated course.
• Accurate assessment of the complete fistulous complex
involves detection of internal & external openings as well the
course of the main tract and its extensions.
• Radiological imaging of the pelvis adds an important
dimension to our understanding of rectal and perianal disease.

7. Dr Ahmed Esawy
A perianal fistula is an abnormal connection between the epithilialised surface of the
anal canal and the skin.
The causes of perianal fistulas:
Primary
Obstruction of anal gland which leads to stasis and infection with abscess and
fistula formation (most common cause).
Secondary
Iatrogenic (hemorrhoideal surgery)
Inflammatory bowel diseases (Crohn's disease more common than colitis ulcerosa)
Infections (viral, fungal or TB)
Malignancy

8. Dr Ahmed Esawy
AETIOLOGY OF ANAL FISTULA
Anal gland theory:
• The majority of anal fistulas are associated with an
abscess caused by an infected anal gland.
• The abscess is formed initially within the intersphincteric
space and then spreads along adjacent potential spaces.
• Common organisms include E. coli, enterococcus species,
and bacteroides species.

9. Dr Ahmed Esawy
Other Causes include:
• I. pelvic sepsis.
• II. Perineal Injuries.
• III Anal disorders:
Fissure.
Hidradenitis.
Hemorrhoids.
• IV-Inflammatory bowel disease:
Crohn‫׳‬s disease.
Ulcerative Colitis.
Actinomycosis.
Venereal infections.

10. Dr Ahmed Esawy
PATHOLOGY OF ANAL FISTULA
• Infection usually affects anal glands at the level of
dentate line.
Spread of infection may occur:
• Downward: → Perianal abscess and intersphincteric
fistula.
• Upward: → Pelvic abscess and suprasphincteric
fistula.
• Outward: → Ischiorectal abscess and
transsphincteric fistula.

11. Dr Ahmed Esawy
THE GOODSALL‫׳‬S RULE
• If the external opening is
anterior to a transverse anal
line the internal opening will
be in a direct straight line to
the nearest crypt.
• If the opening is posterior to
the transverse line, the
internal opening will be in a
posterior midline crypt, and
the tract will be curved.

12. Dr Ahmed Esawy
RADIOLOGICAL ASSESSMENT
• Simple fistula can be easily detected: internal opening,
external opening, and a low tract.
• However complex & recurrent fistulae require accurate
assessment by radiological imaging.
• Fistulography, MRI and EUS have been used with
variable accuracy.

13. Dr Ahmed Esawy
CLINICAL INTERPRETATION
• Main Tract: radial or curvilinear.
• Fistula level: the point in which the main tract of the fistula
traverse the sphincters.
• Internal opening: the point in which the tract traverses the
mucosa- submucosa complex.
• Secondary tract: The direction and the anatomic space were
assessed.
• Chronic fistula cavity: appear as a hypoechoic area thicker
than the main tract, sometimes filled with hydrogen peroxide
(bright hypoechoic).

14. Dr Ahmed Esawy
Anal fistula and perianal
suppurative conditions
The primary tract is presented as a band of poor reflectivity within the
longitudinal muscle (LM) which have external opening and internal opening, the
last is usually difficult to detect on physical examination, but with EAUS the
criteria of internal opening can be easily detected:
The Intersphincteric tract contacts the internal sphincter
A defect is present in the internal sphincter at point of contact with the
intersphincteric tract
There is an actual break in the subepethelial tissue .
Moving the probe in and out within the canal and also circumferentially to
detect the extent of the tract

15. Dr Ahmed Esawy
Classification
The most widely used classification is the Parks Classification which distinguishes
four kinds of fistula: intersphincteric, transsphincteric, suprasphincteric and
extrasphincteric.
The most common fistulas are the intersphincteric and the transsphincteric.
The extrasphincteric fistula is uncommon and only seen in patients who had multiple
operations.In these cases the connection with the original fistula tract to the bowel is
lost.
A superficial fistula is a fistula that has no relation to the sphincter or the perianal
glands and is not part of the Parks classification.These are more often due to Crohns
disease or anorectal procedures such as haemorrhoidectomy or sphincterotomy.

16. Dr Ahmed Esawy
The providential piont is
detection of internal opening

17. Dr Ahmed Esawy
STANDARD
CLASSIFICATION
 Sub cutaneous
 Sub mucous
 Low anal
 High anal
 Pelvi rectal

18. Dr Ahmed Esawy
 Can be
low level fistula- open into anal canal below
the internal ring.
high level fistula- at/ above the internal ring.
 Can be
Simple- without any extensions
Complex- with extensions
 Can be
single
multiple- TB, ulcerative colitis, crohn’s, HIV, LGV

19. Dr Ahmed Esawy
Imaging techniques
• Fistulography
• Endosonography
• CT
• MRI

20. Dr Ahmed Esawy
Simple fistulography

21. Dr Ahmed Esawy
LIMITATION :
• extensions from the primary tract may fail to fill with contrast material if they
are plugged with debris,are very remote, or there is excessive contrast
material reflux from either the internal or external opening
• the sphincter muscles themselves are not directly imaged, which means that
the relationship between any tract and the sphincter must be guessed
• difficult to decide whether an extension has a supra- or an infralevator
location
• the exact level of the internal opening in the anal canal is often impossible to
determine with sufficient accuracy
• Acute tracks may not have a patent lumen
• Difficult to relate the track to the sphincter and levator ani
• Shown to be accurate in only 16 %
• cannot distinguish between the different types of fistula and its exact course
through/in between anal sphincters and also fails to know the integrity of
sphincters
Simple fistulography

22. Dr Ahmed Esawy
Pelvic floor (levator ani muscle ) can be
approximately demarcated by the green line
shown in AP supine view of the pelvis going
through the bases of bilateral greater
trochanters while on lateral view it it lies at the
level of line connecting the tip of coccyx to
inferior border of pubic symphysis.
So any fistula going above this line has to be
supralevator/high fistula and the one which is
below this line will be low anal fistula.

23. Dr Ahmed Esawy

24. Dr Ahmed Esawy
Fistulography in a male patient.
Coronal image shows that it is
obvious that there are several high
extensions (arrows) surrounding
the anorectal junction; however,
the exact anatomic location of
these is unclear because the pelvic
floor (ie, levator ani in this case)
cannot be directly visualized.
Definition of extension location
(supra- or infralevator) is central to
surgical management.
Useful if extra sphincteric
fistula suspected.

25. Dr Ahmed Esawy
Perianal fistulography

26. Dr Ahmed Esawy
A 36 yrs old man with perianal pruritis and discharge since 3-4months. There was a
skin opening in right posterior aspect around the anus CONTINUE
Right perianal blind ending sinus tract
with a small ramification

27. Dr Ahmed Esawy
O mark denotes the external opening on the skin of the fistula/sinus tract. A
small NG tube( 5F) is passed through the opening. So the direction of the tube is
the direction of the tract. Contrast is injected and films are taken in AP and
Lateral views.
Right perianal blind ending sinus tract
with a small ramification
CONTINUE

28. Dr Ahmed Esawy
There is a sinus tract in right perianal fossa and travels superiorly and posteriorly
stopping short of the lumen of anal cannal in posterior midline. It shows a small
ramification along the right anterolateral aspect. No obvious contrast is seen to flow
into the anal canal suggesting lack of communication with the anal canal. END
Right perianal blind ending sinus tract
with a small ramification

29. Dr Ahmed Esawy
 FISTULOGRAPHY/ SINUSOGRAPHY:
• For knowing the exact extent/origin of sinus (or)fistula.
• Water soluble or ultrafluid lipoidal iodine dye is used.
• Lipoidal iodine is poppy seed oil containing 40% iodine.

30. Dr Ahmed Esawy
Fistulography images of horseshoe track in antero-posterior fistulography (A) showing left gluteal
external orifices left horseshoe track communicating left ischiorectal fossa track and hole, right
horseshoe track next to levator ani, which communicates with the internal hole in anterior position,
perianal ipsilateral external orifice and the superficial blindly branch in right large labia [6] that
evolves into new external orifice, observed on admission; and its schematic superposition (B). MRI
image showing the ischiopubic track and left perineal oval fistula extending to the gluteal region (C)
and perianal track and vulvar compromise (D).

31. Dr Ahmed Esawy
Endosonography
Perianal fistula

32. Dr Ahmed Esawy
Fistula classification based on ultrasound
Submucosal
Subcutaneous
The tract is located between the internal sphincter and the skin, without
muscular fibers.
Intersphincteric The tract goes through the intersphincteric space with out traversing the external
sphincter fibers.
Low transsphincteric The tract traverses only the distal external sphincter third, which by
ultrasonography correspond to the lower portion of the medium anal canal.
Medium transsphincteric The tract traverses both sphincters, external and internal, in the lower part of the
medium anal canal, this is in the half closest to the lower anal canal.
High transsphincteric The tract traverses both sphincters, in the higher part of the medium anal canal, in
the space below puborectalis.
Suprasphincteric The tract goes above or through the puborectalis level.
Extrasphincteric The tract affects structures above the sphincters, generally with the internal
opening in the abdominal cavity or the high rectum, this type of fistula usually
cannot be studied by ultrasound.

33. Dr Ahmed Esawy

34. Dr Ahmed Esawy
Simple linear intersphincteric fistulas extend directly from the perianal skin into the
anal canal, sparing both the ischiorectal and ischioanal spaces. These fistulas do
not traverse the external anal sphincter but may traverse the distal most portion of
the internal sphincter below the level of the dentate line.

35. Dr Ahmed Esawy
CLASSIFICATION OF ANAL
FISTULA
A. A superficial fistula.
B. An intersphincteric fistula.
C. A transsphincteric fistula.
D. A suprasphincteric fistula.
E. An extrasphincteric fistula.

36. Dr Ahmed Esawy
A superficial fistula tracks below both the internal anal sphincter and external anal
sphincter complexes
B. An intersphincteric fistula tracks between the internal anal sphincter and the
external anal sphincter in the intersphincteric space.
C. A transsphincteric fistula tracks from the intersphincteric space through the
external anal sphincter.
D. A suprasphincteric fistula leaves the intersphincteric space over the top of the
puborectalis and penetrates the levator muscle before tracking down to the skin.
E. An extrasphincteric fistula tracks outside of the external anal sphincter and
penetrates the levator muscle into the rectum.

37. Dr Ahmed Esawy
Diagram shows different types of fistulous .
On left of image, cephalad line represents extrasphincteric tract running in suprasphincteric
plane before descending to perineum. Middle line shows transsphincteric tract, and caudal line
shows short extrasphincteric tract running directly from anal canal to external opening on perianal
skin. On right of image are two intersphincteric tracts: Cephalad tract ascends in intersphincteric
plane before running suprasphincteric to descend in extrasphincteric plane. More caudal tract on
right descends in intersphincteric plane to skin.

38. Dr Ahmed Esawy
Classification of anal fistulas: perianal fistulas may appear as
(1) superficial fistulas that do not traverse any sphincter muscle.
(2) Fistulas are intersphincteric when they traverse the intersphincteric space or
internal anal sphincter or Transesphincteric
(3) when they extend through the external anal sphincter into the ischioanal space
(4) Spread beyond the external sphincter results in extrasphincteric or
suprasphincteric fistulas

39. Dr Ahmed Esawy
Diagram of the coronal view shows perianal anatomic areas.
A indicates anal canal; R, rectum,
1, submucosal space;
2, intersphincteric space;
3, ischioanal space;
4, supralevator space.

40. Dr Ahmed Esawy
classification of fistulas consists of 5 grades...
.
A, Grade 1: simple linear
intersphincteric fistula B, Grade 2: intersphincteric fistula with
intersphincteric abscess or secondary
fistulas
C, Grade 3: transsphincteric fistula

41. Dr Ahmed Esawy
E, Grade 5: supralevator and translevator
disease.
A indicates anal canal; and R, rectum.
D, Grade 4: transsphincteric fistula
with abscess or secondary track within
the ischioanal or ischiorectal fossa

42. Dr Ahmed Esawy
Congenital :
Perianal fistula has been reported in early infancy. And in some cases the
tracks are lined by columnar or transitional epithelium, suggesting that they
might have a congenital or developmental origin

43. Dr Ahmed Esawy
Illustration in coronal plane shows fistula extensions (secondary tracts):
A extension into roof of ischioanal fossa, arising from apex of a transsphincteric fistula;
B supralevator pararectal extension arising from apex of a transsphincteric fistula;
C supralevator extension originating from intersphincteric plane,
D intersphincteric horseshoe

44. Dr Ahmed Esawy
TECHNIQUE OF EUS
in AF with contrast
• While the patient in the left lateral position a conventional
EUS is performed.
• The probe should be introduced at the higher, middle, and
lower third of the anal canal.
• Fistula appears as hypoechoic areas within the submucosa,
internal or external sphincter, or perianal tissue.
• A catheter is inserted into the external opening.
• Hydrogen peroxide is first injected slowly to show the main
tract, then, injection at a greater pressure was performed to
detect secondary tracts.

45. Dr Ahmed Esawy
THE PRACTICAL USES OF EUS WITH H2O2
• EUS is beneficial in detecting the course of the primary
tract . Moreover, endosonography is cost-effective and
superior in diagnosing trans-sphincteric fistula and
exclude secondary tracts.
• EUS can detect the site & number of the internal opening.
• Identification of those high fistulae that will be
subsequently treated with a sphincteric saving procedure.
• Detection of chronic fistula complex or secondary tracts.

46. Dr Ahmed Esawy
• Comparing MRI with endoanal ultrasound with
H2O2, it seems that the latter has certain advantages:
it is cheap, simple, quick (takes less than 10 minutes)
and is portable (can be performed in the operating
room).
• Thus, EUS has a degree of reliability high enough to
be considered the preferred examination technique in
the study of complex anal fistulae.

47. Dr Ahmed Esawy
Endoanal ultrasound
Limitation
• Operator dependent
• Highly accurate at identifying the
internal opening
• Depicts fewer secondary extensions
than MR
• Difficulty differentiating active track
from fibrosis

48. Dr Ahmed Esawy
INTERSPHINCTERIC
FISTULA
• Intersphincteric fistula
(yellow track) extending
from the dentate line down
to the skin through the
intersphincteric plane.

49. Dr Ahmed Esawy
After administration of peroxide, EUS scan shows immediate
extension to the anal lumen, below the level of the
internal anal sphincter (arrow).

50. Dr Ahmed Esawy
The fistula tracks upward below the internal sphincter (arrowhead ),
tracks posteriorly into the intersphincteric plane (arrow ).
It forms a second track in the intersphincteric region (arrows ).

51. Dr Ahmed Esawy
Simple transsphincteric fistula. After
administration of peroxide, endoanal US scan
shows a direct communication that extends from
the skin immediately adjacent to the anal canal
(small arrow) through the distal aspect of the
posterior internal anal sphincter (arrowhead) to
the anal canal (large arrow). Echogenic air is
trapped in the anal mucosa anteriorly, which
may falsely suggest communication at this
location. After demonstration of this single
superficial posterior fistula, the patient
underwent an unroofing procedure only, with no
loss of continence
Simple transsphincteric fistula. Drawing in the coronal
plane, with a horizontal line corresponding to the level of the
US image, shows extent of the fistula depicted in a.

52. Dr Ahmed Esawy
Intersphincteric fistula. Anal endosonogram in transverse plane at mid–anal canal
level in a male patient shows fistula with hypoechoic tract located in intersphincteric
plane between external (EAS) and internal (IAS) anal sphincters. Internal sphincter is
markedly hypoechoic. At surgery, the internal opening was located at 6 o’clock
posteriorly and was correctly predicted from anal endosonographic visualization
because of the radial position of the fistula within the intersphincteric plane.

53. Dr Ahmed Esawy
Complex intersphincteric fistulas are associated with abscesses or secondary tracks
and are limited by the external anal sphincter
Intersphincteric fistula. (a)
After administration of
peroxide, endoanal US scan
shows immediate extension
to the anal lumen, below the
level of the internal anal
sphincter (arrow).
(b, c) The fistula also
tracks upward below the
internal sphincter
(arrowhead in b), tracks
posteriorly into the
intersphincteric plane
(arrow in b), and forms a
second track in this
intersphincteric region
(arrows in c).
(a)
(b)

54. Dr Ahmed Esawy
Intersphincteric fistula: Drawing in the coronal plane, with horizontal lines
corresponding to the levels of the US images, shows extent of the
intersphincteric fistula depicted in a-c

55. Dr Ahmed Esawy
Line diagram of the coronal view shows a right intersphincteric fistula ( track)
extending from the dentate line down to the skin through the intersphincteric
plane

56. Dr Ahmed Esawy
Vertical submucosal and intersphincteric extensions
Vertical submucosal and intersphincteric extensions. (a) Despite an
unremarkable initial endoanal US examination, US scan obtained after
peroxide injection into a superficial posterior opening shows a fistula
extending through both the markedly thinned internal (shortest arrow)
and external anal sphincters, communicating with the anal lumen, and
tracking in both the submucosal and intersphincteric spaces (long
arrows).
Vertical submucosal and
intersphincteric extensions.
(b) US scan shows that, in
the middle of the anal canal,
approximately 2 cm more
cranial than image in a,
additional tracks extend
vertically in the submucosal
(shortest arrow) and
intersphincteric spaces (long
arrows).
(c)
(c) Drawing in the coronal plane, with
horizontal lines corresponding to the levels
of the US images, shows extent of the
fistula and additional tracks

57. Dr Ahmed Esawy
TRANSSPHINCTERIC FISTULA
• Trans-sphincteric
fistula (yellow track)
crossing the
ischiorectal fossa and
piercing both layers of
the sphincter complex.

58. Dr Ahmed Esawy
Transsphincteric fistula extending through
the internal anal sphincter. Prior to
injection of peroxide, endoanal US scan
shows a hypoechoic soft-tissue
abnormality (large arrow) superficial to the
anterior part of the internal anal sphincter
(small arrow).
Transsphincteric fistula
extending through the
internal anal sphincter. (b)
After cannulation of the
fistula and injection of
peroxide, prompt
visualization of the
peroxide was noted in this
fistula, which extends
through the internal anal
sphincter into a small
superficial submucosal
abscess cavity (arrow).
(c) Drawing in the coronal
plane, with a horizontal line
corresponding to the level of
b, shows the extent of the
transsphincteric fistula and
abscess

59. Dr Ahmed Esawy
Transsphincteric fistula extending through the
external anal sphincter and communicating with
an intersphincteric abscess. (a) Peroxide-
enhanced endoanal US scan reveals a
transsphincteric fistula communicating with a
small yet high posterior intersphincteric abscess
cavity (arrow). No peroxide traverses the internal
sphincter, and no communication with the anal
lumen was identified
(b) Drawing in the coronal
plane, with a horizontal line
corresponding to the level
of a, shows the extent of
the fistula and abscess

60. Dr Ahmed Esawy
Transsphincteric fistula extending through the internal
and external anal sphincters. (a) Peroxide-enhanced
endoanal US scan shows extension of the fistula
through the external anal sphincter into a small
abscess within the posterior aspect of the internal
anal sphincter (arrow). No communication with the
anal canal was identified at subsequent surgery.
(b) Drawing in the coronal
plane, with a horizontal line
corresponding to the level of
a, shows extent of the fistula
and abscess.

61. Dr Ahmed Esawy
Transsphincteric fistula. (a) Preliminary
ultrasound scan reveals a hypoechoic soft-
tissue mass in the left lateral
intersphincteric plane (large arrow) with
marked deficiency of the internal sphincter
posteriorly (small arrow).
Transsphincteric fistula. (b) After peroxide
injection, the US scan shows immediate
communication with this abscess (large arrow),
with the fistula extending through the thickened
and irregular internal anal sphincter antrolaterally
into the anal canal (small arrow).
(c) Drawing in the coronal plane, with a
horizontal line corresponding to the
level of b, shows extent of the fistula
and abscess

62. Dr Ahmed Esawy
Transsphincteric fistula shown on anal endosonogram in the transverse plane at the
mid–anal canal level in a female patient. In contrast to Figure before, the fistula () has
penetrated the external anal sphincter (EAS). The internal opening was correctly
predicted at 7-o’clock position. Note that the internal sphincter is relatively thinned here,
which is a clue to the site of the internal opening, but there is no tract extending to the
anal mucosa.

63. Dr Ahmed Esawy
• EUS shows a direct communication that extends from
the skin immediately adjacent to the anal canal (small
arrow) through the posterior internal sphincter
(arrowhead) &to the anal canal (large arrow).

64. Dr Ahmed Esawy
• Trans-sphincteric fistula with
an ischiorectal abscess (a).

65. Dr Ahmed Esawy
• Transsphincteric fistula extending through the
internal anal sphincter. Prior to injection of peroxide,
EUS scan shows a hypoechoic soft-tissue abnormality
(large arrow) superficial to the internal sphincter
(small arrow).

66. Dr Ahmed Esawy
• After injection of peroxide, contrast is seen extending
through the internal sphincter into a small superficial
submucosal abscess cavity (arrow).

67. Dr Ahmed Esawy
• Transsphincteric fistula. EUS reveals a hypoechoic
soft-tissue mass in the lateral intersphincteric plane
(large arrow) with marked deficiency of the internal
sphincter posteriorly (small arrow).

68. Dr Ahmed Esawy
• Transsphincteric fistula. After peroxide injection, EUS
shows immediate communication with this abscess (large
arrow), with the fistula extending through the thickened and
irregular internal anal sphincter antrolaterally into the anal
canal (small arrow).

69. Dr Ahmed Esawy
Grade 4 transsphincteric fistula with abscess. A, Axial (left) and sagittal (right) endoanal sonograms show a transsphincteric
fistula with an abscess within ischioanal fossa at the 2-o’clock position. B and C, Axial and sagittal magnified endoanal
sonograms show the intersphincteric component of the abscess (a) at the 12-o’clock position. In C, the IAS is shown
between black arrows,and the EAS is shown between white arrows. D, Diagram of the coronal plane shows the extent of the
transsphincteric fistula depicted in A–C. A indicates anal canal; and R, rectum.

70. Dr Ahmed Esawy
HORSESHOE FISTULAS
• Horseshoe fistulas.
Drawing in the coronal
plane, shows extent of
the fistulas and abscess.

71. Dr Ahmed Esawy
Horseshoe fistulas
Horseshoe fistulas. (a) Preliminary endoanal US scan reveals irregular thickening
with a soft-tissue mass (arrow) at the 11-o’clock position in the internal anal
sphincter and the intersphincteric plane
Horseshoe fistulas. (b, c) After peroxide injection, the US scans show immediate
communication (arrow in b), with fistulas extending posteriorly in the external anal
sphincter (large arrow in c) and through the internal anal sphincter into the anal
lumen (small arrow in c).
Horseshoe fistulas. (d) Drawing in the
coronal plane, with horizontal lines
corresponding to the levels of b and c,
shows extent of the fistulas and abscess

72. Dr Ahmed Esawy
Anal endosonogram at upper anal canal level in a male patient shows extensive
hypoechoic horseshoe extension (). Because endosonography is limited to the
transverse plane, it is difficult to determine whether this extension is infra- or
supralevator.

73. Dr Ahmed Esawy
Transverse anal endosonogram at upper anal canal level in a female patient
shows intersphincteric horseshoe extenstion (arrows). Gas in the fistula causes
acoustic shadowing (stars), which could be mistaken for transsphincteric tracts.

74. Dr Ahmed Esawy
• Horseshoe fistulas. EUS scan reveals irregular
thickening with a soft-tissue mass (arrow) at the 11-
o’clock position in the internal sphincter and the
intersphincteric plane.

75. Dr Ahmed Esawy
Suprasphincteric fistula
• Suprasphincteric fistula. After injection of peroxide,
a US scan shows an intersphincteric abscess
posteriorly (large arrow) immediately external to the
internal anal sphincter (small arrow).

76. Dr Ahmed Esawy
Suprasphincteric fistula : It appears as hypoechoic tract extending up to a level
above puborectalis and then extend down through the levator ani muscle to
reach skin (Jonathan et al., 2000).
Suprasphincteric fistula: (a) after injection of peroxide, US scan shows an intersphincteric abscess posteriorly (large arrow) immediately external to
the internal anal sphincter (small arrow). (b, c) Subsequent scans show secondary fistulas extending from this abscess through the right side of the
internal anal sphincter into the anal lumen at the level of the puborectal muscle (arrow in b) and through the levator ani muscle superiorly (arrows in
c). (d) Drawing in the coronal plane, with horizontal lines corresponding to the levels of the US images, shows extent of the abscess and fistulas
(Quoted from Jonathan et al., 2000).

77. Dr Ahmed Esawy
Grade 5 suprasphincteric fistula and abscesses. A, Endoanal sonogram shows an
ischioanal abscess at the 3- to 6-o’clock position (black arrows) and its
transsphincteric extension through both the markedly thinned EAS and IAS (white
arrows) at the level of the middle anal canal. B, After cannulation of the fistula and
injection of peroxide, on a subsequent endoanal sonogram through the high anal
canal level, prompt visualization of the peroxide was noted in the abscess (black
arrows) and fistula extending through both the markedly thinned IAS and puborectalis
muscle (PRM), which extends into a small superficial submucosal abscess cavity
(white arrows) CONTINUE

78. Dr Ahmed Esawy
C, Endoanal sonogram through the supralevatoric level obtained before administration of
peroxide reveals a horseshoe supralevatoric abscess cavity (black arrows) and a deficiency area
in the rectal wall at the 6-o’clock position (white arrow). A, After peroxide injection, an endoanal
sonogram clearly depicts the suprasphincteric abscess cavity (black arrows) communicating with
the anal lumen (white arrow) at the same location as in C. The internal opening is shown as a
subepithelial breach connecting with the intersphincteric tract through an internal sphincteric
defect. E, Diagram in the coronal plane shows the extent of the suprasphincteric fistula depicted
in A–D. A indicates anal canal; and R, rectum
C E
Grade 5 suprasphincteric
fistula and abscesses

79. Dr Ahmed Esawy
EXTRASPHINCTERIC FISTULA
• Extrasphincteric fistula. EUS scan shows a single
hypoechoic mass (large arrow) outside the internal (small
arrow) and external sphincters prior to peroxide injection.

80. Dr Ahmed Esawy
• Exrtrasphincteric fistula. US scans obtained after
injection show immediate communication with this
small abscess cavity (arrow), with a fistula (arrow)
tracking up the antrolateral rectal wall to the base of
the prostate gland.

81. Dr Ahmed Esawy
Extrasphincteric fistula. (a) Endoanal US
scan shows a single hypoechoic mass
(large arrow) outside the internal (small
arrow) and external anal sphincters prior to
peroxide injection
Extrasphincteric fistula. (b, c) US scans
obtained after injection show immediate
communication with this small abscess
cavity (arrow in b), with a fistula (arrow in
c) tracking up the antrolateral rectal wall to
the base of the prostate gland (P in c).
Extrasphincteric fistula. (d) Drawing in the
coronal plane, with horizontal lines
corresponding to the levels of b and c,
shows extent of the fistula and abscesses

82. Dr Ahmed Esawy
Extrasphincteric and suprasphincteric fistulas
Suprasphincteric fistula. (a) After injection of peroxide, a US
scan shows an intersphincteric abscess posteriorly (large arrow)
immediately external to the internal anal sphincter (small arrow).
Suprasphincteric fistula. (b, c) Subsequent
scans show secondary fistulas extending
from this abscess through the right side of
the internal anal sphincter into the anal
lumen at the level of the puborectal muscle
(arrow in b) and through the levator ani
muscle superiorly (arrows in c).
Suprasphincteric fistula. (d)
Drawing in the coronal plane, with
horizontal lines corresponding to
the levels of the US images, shows
extent of the abscess and fistulas.

83. Dr Ahmed Esawy
PERIANAL FISTULA
Use of peroxide-enhanced anal endosongraphy allows visualization of entire
course of the echogenic fistula, including its relation to the internal and
external sphincters and the levator ani muscle

84. Dr Ahmed Esawy
Sometimes it is difficult to differentiate between a tract and small collection at one
level ,but this can be overcome by moving and angling the probe ,as both tend to be
hypoechoic, but tracts often have hyperechoic shadows in the middle which represent
gas within the tract

85. Dr Ahmed Esawy
anorectal abscesses

86. Dr Ahmed Esawy
• Pelvic abscess (a) with a
translevator fistula
traversing the ischiorectal
fossa.

87. Dr Ahmed Esawy
INTERSPHINCTERIC ABSCESS
• Intersphincteric abscess (a).

88. Dr Ahmed Esawy
• Posterior intersphincteric abscess. A hypoechoic soft-
tissue mass containing air immediately posterior to the
anal canal in the intersphincteric zone (arrow).

89. Dr Ahmed Esawy
Posterior intersphincteric abscess. (a) Endoanal US
scan obtained before administration of peroxide reveals
marked deficiencies of numerous areas of the internal
anal sphincter, with a hypoechoic soft-tissue mass
containing air immediately posterior to the anal canal in
the intersphincteric zone (arrow).
Posterior intersphincteric abscess (b)
Scan obtained after peroxide injection
shows prompt communication with this
intersphincteric abscess (arrow).

90. Dr Ahmed Esawy
Posterior intersphincteric abscess: (a) Endoanal US scan obtained before administration
of peroxide reveals marked deficiencies of numerous areas of the internal anal
sphincter, with a hypoechoic soft-tissue mass containing air immediately posterior to the
anal canal in the intersphincteric zone (arrow). (b) Scan obtained after peroxide injection
shows prompt communication with this intersphincteric abscess (arrow)

91. Dr Ahmed Esawy
PERIANAL ABSCESS

92. Dr Ahmed Esawy
Transperineal US demonstrating
anal fistula

93. Dr Ahmed Esawy
MRI IN FISTULA

94. Dr Ahmed Esawy
Magnetic Resonance
• Most accurate technique for
evaluation of the primary track and
any extensions.
• More accurate predictor of patient
outcome than surgical findings at
EUA].

95. Dr Ahmed Esawy
Endoanal coil
• Endocoils give superior anatomical resolution of fistula disease
within the sphincter
• Resolution falls off rapidly outside the sphincter
• Complex tracks outside the sphincter are not well seen

96. Dr Ahmed Esawy
Correct orientation for MR imaging of anal canal. Sagittal T2-weighted scout image
through patient’s midline is used to plan images that are truly transverse with
respect to anal canal,as shown by white lines. Coronal imaging is then
performed at 90° to the transverse plane.

97. Dr Ahmed Esawy
MRI protocol
• T1W &T2W fse axial and coronal
• T2W with fat sat
• T1W + CM
• FOV 200
• IV gadolinium rarely administered

98. Dr Ahmed Esawy
• T2W ----- anatomy
• T2W with fat sat ---- fistula

99. Dr Ahmed Esawy
The anal clock
P: anterior
perineum
n: natal cleft

100. Dr Ahmed Esawy
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

101. Dr Ahmed Esawy
T2W images without fat sat better display the anatomy, while the fat sat images
better depict the fistulas.
Perianal fistula: axial T2WI without fatsat (left) and with fatsat (right)

102. Dr Ahmed Esawy
Reporting
When you describe a fistula, it is important to mention the following characteristics:
Position of the mucosal opening on axial images (using the anal clock).
Distance of the mucosal defect to the perianal skin on coronal images.
Secondary fistulas or abscesses.

103. Dr Ahmed Esawy
Classification
Parks classification
1- intersphincteric
2- transsphincteric
3- extrasphincterisc
4-suprasphincteric
Intersphincteric & transsphincteric are the most common
Intersphincteric --> 70 %
Transsphincteric -->20%

104. Dr Ahmed Esawy

105. Dr Ahmed Esawy
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

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108. Dr Ahmed Esawy
Grade 1 simple linear intersphincteric fistula. (a) Line diagram of the coronal
view shows a right intersphincteric fistula (yellow track) extending from the
dentate line down to the skin through the intersphincteric plane.

109. Dr Ahmed Esawy
Intersphincteric fistula
On the left axial T2W images with and without fat
saturation.
An intersphincteric fistula is located at 6 o'clock.
Continue with coronal images.
On the coronal image the fistula runs caudally
towards the skin. There is no connection with the
external sphincter.

110. Dr Ahmed Esawy
coronal images
of another
patient with an
intersphincteric
fistula.

111. Dr Ahmed Esawy
Grade 1 Intersphincteric fistula perianal
fistula. Coronal dynamic contrast-
enhanced MR image shows a right
intersphincteric fistula entering the anal
canal in the midline posteriorly (arrow).
Grade 1 perianal fistula. Axial T2-
weighted
MR image shows a posterior midline
intersphincteric fistula (arrowhead).

112. Dr Ahmed Esawy
Intersphincteric fistula: are usually simple hypoechoic tract in intersphincteric
space but may be associated with secondary tracts
Intersphincteric fistula: (a) after administration of peroxide, endoanal US scan shows immediate
extension to the anal lumen, below the level of the internal anal sphincter (arrow). (b, c) The
fistula also tracks upward below the internal sphincter (arrowhead in b), tracks posteriorly into the
intersphincteric plane (arrow in b), and forms a second track in this intersphincteric region
(arrows in c). (d) Drawing in the coronal plane, with horizontal lines corresponding to the levels of
the US images, shows extent of the intersphincteric fistula depicted in a-c

113. Dr Ahmed Esawy
Intersphincteric fistula in a male
patient. Transverse STIR MR image
shows that lateral margin of external
sphincter (long arrow) contrasts against fat
in the ischioanal fossa (star). Fistula (short
arrow) is in the intersphincteric space
posteriorly at 6 o’clock and is contained by
the external sphincter. There is no tract in
the ischioanal fossa.

114. Dr Ahmed Esawy
Perianal fistula with an abscess

115. Dr Ahmed Esawy
Grade 1- Intersphincteric
fistula

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Grade 2 horseshoe perianal
fistula. Line diagram of the
axial view shows an
intersphincteric horseshoe
fistula (yellow track, arrow)
confined by the external
sphincter.
Grade 2 horseshoe perianal
fistula. Axial T2-weighted image
shows an intersphincteric
horseshoe fistula (arrow).
Grade 2 :
horseshoe intersphincteric
fistula with abscess or 2ry track

125. Dr Ahmed Esawy
Horseshoe extension (arrows) arising
from intersphincteric fistula in a male
patient Transverse STIR MR image
shows that, in this case, the
horseshoe practically encircles the
anal canal.

126. Dr Ahmed Esawy
Horseshoe fistula where the internal opening is seldom clearly defined which
may fuse with IAS and it is rare to see any actual defect in the submucosa
(Jonathan et al., 2000).
Horseshoe fistulas: (a) Preliminary endoanal US scan reveals irregular thickening with a soft-tissue mass (arrow) at the 11-o’clock
position in the internal anal sphincter and the intersphincteric plane. (b, c) After peroxide injection, the US scans show immediate
communication (arrow in b), with fistulas extending posteriorly in the external anal sphincter (large arrow in c) and through the internal
anal sphincter into the anal lumen (small arrow in c). (d) Drawing in the coronal plane, with horizontal lines corresponding to the levels of
b and c, shows extent of the fistulas and abscess (Quoted from Jonathan et al., 2000).

127. Dr Ahmed Esawy
Grade 2 perianal fistula with an
abscess. Coronal dynamic contrast-
enhanced MR image shows a left
intersphincteric abscess cavity
(arrowhead) above the primary
intersphincteric track (curved arrow).
The enteric entry point is suggested
by a medial track (straight arrow).
Grade 2 perianal fistula with an
abscess. Line diagram of the coronal
view shows a left intersphincteric
abscess (a).

128. Dr Ahmed Esawy
Grade 2 horseshoe perianal fistula with an abscess. (a)coronal, (b) axial,
dynamic contrast-enhanced MR images show an intersphincteric abscess, which
is peripherally enhanced (curved arrow) and contains a central focus of
nonenhancing pus (straight arrow). As viewed in all three planes, the fistula is
confined by the external sphincter and the ischiorectal fossa is unaffected

129. Dr Ahmed Esawy
Grade 2 perianal fistula with an abscess.
dynamic contrast-enhanced MR images show an intersphincteric abscess, which
is peripherally enhanced (curved arrow) and contains a central focus of
nonenhancing pus (straight arrow). As viewed in all three planes, the fistula is
confined by the external sphincter and the ischiorectal fossa is unaffected.

130. Dr Ahmed Esawy
Grade 2- Intersphincteric fistula
with collection

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132. Dr Ahmed Esawy
Grade 3 perianal fistula. Line diagram of the coronal view shows a right trans-
sphincteric fistula (yellow track) crossing the ischiorectal fossa and piercing both
layers of the sphincter complex
Grade 3 :
transsphincteric fistula

133. Dr Ahmed Esawy
Grade 3 Trans-sphincteric fistula perianal
fistula. Coronal dynamic contrast-
enhanced MR image shows a right trans-
sphincteric fistula (arrow) and
inflammatory change in the right
ischiorectal fossa. Note the entry site in the
middle
third of the anal canal
Grade 3 perianal fistula. Axial dynamic
contrast-enhanced MR image shows a left
trans-sphincteric fistula within the
ischiorectal fossa and piercing the
external sphincter (arrow).

134. Dr Ahmed Esawy
Trans-sphincteric fistula: appears as extension through the EAS is most important to
recognize, and is clearly shown as an irregular poorly reflective finger like
extensions from the primary tract running through the EAS, and disrupting its
normal architecture (Jonathan et al., 2000)
Transesphincteric fistula: extending through the internal and external anal
sphincters. (a) Peroxide-enhanced endoanal US scan shows extension of the fistula
through the external anal sphincter into a small abscess within the posterior aspect
of the internal anal sphincter (arrow). (b) Drawing in the coronal plane, with a
horizontal line corresponding to the level of a, shows extent of the fistula and
abscess

135. Dr Ahmed Esawy
Transsphincteric fistula
axial T2WI and T2WI + fatsat of a transsphincteric fistula.
The defect through the internal and external sphincter at 6 o'clock is clearly visible
and more apparent on the fat sat images.

136. Dr Ahmed Esawy
axial T2W-fatsat images of a transsphincteric fistula with the mucosal opening at 11
o'clock.

137. Dr Ahmed Esawy
Coronal (a) T2-weighted fast spin-echotion thickness, 4 mm; gap, 0.4 mm) and (b)
coronal STIR (4000/42, inversion time of 150 msec; echo train length, 16; matrix,
224256; section thickness, 4 mm; gap 0.4 mm; two signals acquired)
MRimages acquired with external phased-array coil show complex transsphincteric
fistula with tract (short straight arrows) in left ischioanal fossa that extends below
ischial bone (I) toward the upper leg (not shown). At the ischial tuberosity, bone
marrow edema (long straight arrow) is visible on b. Arrowheadexternal opening,
curved arrowsmall abscess, AS anal sphincter

138. Dr Ahmed Esawy
Transsphincteric fistula in a male patient. Transverse STIR MR image shows primary
tract (vertical arrow) in right ischioanal fossa, where it can be clearly seen to penetrate
external sphincter (star) to reach the intersphincteric space. Internal opening is posterior
at 6 o’clock (horizontal arrow), at dentate line level.

139. Dr Ahmed Esawy
Transsphincteric fistula in a male
patient. Transverse STIR MR image at
level of the internal opening shows
primary tract (vertical arrow) at 4 –5
o’clock. Unlike image before, the tract
cannot be traced right to the anal
mucosa, and the adjacent internal
sphincter (horizontal arrow) appears
intact. However, an internal opening at
4 –5 o’clock was reported because this
position indicated site of maximal
infection in the intersphincteric
plane.The internal opening was
confirmed at this site
during subsequent EUA.
Intersphincteric plane is well seen in
this patient between hyperintense
internal sphincter and the external
sphincter.

140. Dr Ahmed Esawy
Left-sided transsphincteric
tract (short arrow) in a female
patient. Coronal STIRMR
image shows large extension
(long arrow) from apex of tract
into roof of ipsilateral
ischioanal fossa.

141. Dr Ahmed Esawy
Left-sided transsphincteric fistula (short straight arrows) with internal opening at 6
o’clock (long straight arrow) in a female patient. Transverse STIR MR image shows
remote extension (curved arrow) into ipsilateral buttock that was unsuspected at
clinical examination but is well demonstrated atMRimaging. The
extension was found at surgery guided byMRfindings.

142. Dr Ahmed Esawy
Transsphincteric primary tract (short arrow) in the right posterior quadrant of a
female patient. Transverse STIRMRimage shows two left-sided contralateral extensions
(long arrows) that were undetected at EUA until results of patient’s MR examination
were revealed to the surgeon in the operating theater.

143. Dr Ahmed Esawy
Grade 3- Trans-sphincteric
fistula

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Grade 4 perianal fistula with an
ischiorectal fossa abscess. Line
diagram of the coronal view
shows a left trans-sphincteric
fistula with a left ischiorectal
fossa abscess (a).
coronal dynamic contrast- enhanced MR
image shows a left trans-sphincteric fistula
(arrow) with a left ischiorectal fossa
abscess (arrowheads) containing
nonenhancing pus
Grade 4: transsphinteric fistula with abscess or
2ry track within ischeorectal fossa

180. Dr Ahmed Esawy
Grade 4 perianal fistula with
an ischiorectal fossa abscess. Axial
dynamic contrast- enhanced MR
image shows a left trans-sphincteric
fistula (arrow) with a left ischiorectal
fossa abscess
(arrowheads) containing
nonenhancing pus.
Grade 4: Trans-sphincteric Fistula
with Abscess or
Secondary Track within the
Ischiorectal Fossa
Grade 4 perianal fistula with an abscess.
Line diagram of the axial view shows a left
trans-sphincteric fistula and left ischioanal
fossa abscess (a).

181. Dr Ahmed Esawy
. Grade 4 perianal fistula with an
abscess. Line diagram of the axial view
shows intersphincteric and ischioanal fossa
components of the abscess (a).
Grade 4 perianal fistula with an abscess.
Axial T2-weighted MR image shows a left
trans-sphincteric fistula (straight arrow)
with intersphincteric and left ischioanal
fossa components of the abscess (curved
arrows).

182. Dr Ahmed Esawy
Grade 4- Trans-sphincteric fistula
with secondary track

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187. Dr Ahmed Esawy
Grade 5 perianal fistula. Coronal
dynamic contrast-enhanced MR image
shows a right translevator fistula
(straight arrow) with extensive
supralevator horseshoe ramification
(curved arrows).
Grade 5: Supralevator and Translevator Disease:
Grade 5 perianal fistula with an
abscess. Line diagram of the
coronal view shows a pelvic
abscess (a) with a translevator
fistula traversing the ischiorectal
fossa.

188. Dr Ahmed Esawy
Bilateral supralevator extensions (long arrows) in a female patient. Coronal STIR
MRimage clearly show levator plates (short arrows) bilaterally, so that it is easy for
the radiologist to be confident that infection extends above them.

189. Dr Ahmed Esawy
Grade 5- Translevator
disease

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suprasphincteric fistula.
There are two tracts in the ischioanal region.
The right sided tract runs over the puborectal muscle (asterisk) and the mucosal
opening lies at the level of the linea dentata (black arrow).

195. Dr Ahmed Esawy
coronal T2W-images of a small abscess in the left ischioanal fossa, the fistula runs
through the levator ani.
It is therefore above the sphincter complex and extrasphincteric.

196. Dr Ahmed Esawy
Fistula classified as extrasphincteric
in a female patient on coronal T2-
weighted MR image. Fistula tract
(horizontal white arrows) is seen in
left ischioanal fossa. Levator plates
(vertical white arrows) are well
depicted bilaterally. Tract penetrates
the left levator plate, and the internal
opening (top horizontal
white arrow) is into the rectum,
above the level of the puborectalis
muscle () and well above the dentate
line (black arrow).

197. Dr Ahmed Esawy
complex fistula.
Two tracts in the left
buttock form a single
tract (no. 1-2).
This fistula breaks
through the external
sphincter (no. 4).
In the intersphincteric
space it divides again
into two tracts (no. 5).
One ends blindly in
the intersphincteric
space (no. 6).
The other breaks
through the internal
sphincter with the
mucosal defect at 1
o'clock.

198. Dr Ahmed Esawy
perianal fistula who has Crohn's disease.
Continue with the coronal images.
On the coronal images the thickening of
the bowel wall is demonstrated.
Axial fatsat images depict the transmural
inflammation with infiltration of the
mesenteric fat.
Crohn's disease

199. Dr Ahmed Esawy
Transsphincteric fistula in a man with Crohn disease. (a, b) Transverse T2-weighted fast
spin-echo MR images two signals acquired) obtained (a) without and (b) with fat
saturation and (c) transverse fat-saturated contrast-enhanced T1-weighted fast spin-
echo image (see Table for parameters) show two separate fistula tracts (straight and
curved arrows) in left posterior ischioanal space, close to the anal sphincter (A). Both
tracts show confluent high signal intensity centrally, which represents pus in the tract
lumen. On a and b,the surrounding inflammatory tissue (arrowheads) is of low signal
intensity (a), which increases with fat-saturation (b) and especially with contrast
enhancement (c).Anterior tract (curved arrow) demonstrates more adjacent inflammation
(arrowheads) than does posterior tract (straight arrow).

200. Dr Ahmed Esawy
Intrapelvic disease in with Crohn perianal fistulas. Sagittal T2-weighted two-
dimensional turbo MR image shows a presacral fluid collection (arrow) with
connection to the bladder (not shown) and sigmoid colon (arrowhead) that was
correctly diagnosed as a presacral abscess that drained to the bladder and
sigmoid colon.

201. Dr Ahmed Esawy
CT
FISTULOGRAPHY

202. Dr Ahmed Esawy
21-year-old male with perianal complex
fistulas.
CT fistulography images clearly show
complex perianal fistula tracts in
subcutaneous shallow area, in rear of
coccyx. Three anomalous fistula tracts with
external opening were successfully
identified. Extent of disease and
complicated spatial information are better
seen on volume rendering image. Minute
fistula was not clearly seen

203. Dr Ahmed Esawy
show complicated spatial
information of two separate fistula
tracts (short white arrows) with
irregularly shaped abscess (* in C),
which closes to mid-anal canal.
Internal tiny ramifications (long
white arrows in C) are not exactly
confirmed at corresponding position
on MR image. Fistula cavities are
surrounded by inflammatory tissue
(fistula wall, + in A, B). Irregular
shape of abscess (* in B).
44-year-old female with recurrent fistulas after two operations.
CT fistulography (A, C) and MR imaging (contrast-enhanced T1-weighted
with fat suppression in B): reconstructed images clearly

204. Dr Ahmed Esawy
64-year-old male with perianal
complex fistulas.
CT fistulography (B, C) and MR
imaging (contrast-enhanced T1-
weighted with fat suppression in
A): reconstructed images clearly
show complicated spatial
information of fistula tract (short
white arrows). Latent secondary
extensions (long white arrows in
B, C) are clearly confirmed on CT
but not corresponding MR image
(long white arrow in A).

205. Dr Ahmed Esawy
64-year-old male with extrasphincteric fistula.
MR imaging (T2-weighted with fat suppression in A) and CT fistulography (B): internal
opening (short white arrow in A, B) of fistula (+ in A, B) is well identified in
corresponding MR and CT images; confirmation of internal opening is major surgical
aim.

206. Dr Ahmed Esawy
64-year-old male with perianal complex fistulas.
MR imaging (contrast-enhanced T1-weighted with fat suppression in A) and CT
fistulography (B): internal opening (short white arrow in A, B) of fistula (+ in A, B) is
well identified in corresponding MR, CT images.

207. Dr Ahmed Esawy
38-year-old male with semi-
horseshoe fistula.
CT fistulography (D-G) and MR
imaging (T2-weighted with fat
suppression in A-C): transverse,
coronal images clearly show
circumferential spread of fistula
(short white arrows in A-G). Extent
of disease and complicated spatial
information are better seen on
volume rendering image (short
arrows in G). External opening
(long white arrow in B, E, G),
internal opening (short black arrow
in D), and secondary ramification
(long black arrow in C, F) are
seen.

208. Dr Ahmed Esawy
26-year-old male with fistula.
MR imaging (T1-weighted with fat suppression in A, T2-weighted with fat suppression in C) and
CT fistulography (B): fistula (short white arrow in A, B) spreads backward to skin’s surface with
evident external opening. Tenuous internal opening (long white arrow in C) was successfully
identified on MR image. Internal opening is confirmed clearly on MR image but not
corresponding CT image, owing to lack of contrast agent filling.

209. Dr Ahmed Esawy
25-year-old female with fistula.
MR imaging (T2-weighted with fat suppression in A, contrast-enhanced liver acquisition
with volume acceleration in C) and CT fistulography (B). Fistula (short white arrows in
C) perforating backward toward anal sphincter, spreads (short white arrow in A)
backward to skin’s surface with evident external opening (long white arrow in A, B).
Fistula is confirmed clearly on MR image but not corresponding CT image, owing to lack
of contrast agent filling.

210. Dr Ahmed Esawy
54-year-old female with
fistula caused by ruptured
teratoma in pelvic cavity.
MR imaging (contrast
enhanced T1-weighted with
fat suppression in A, C; T2-
weighted without fat
suppression image in B),
and CT fistulography (D-F):
mass (teratoma, short white
arrows in A-F) perforates
levator ani muscle
downward, entering perianal
spaces. Images (A-F)
provide excellent imaging of
fistula (long white arrow in C,
F), teratoma, and their
relationship to adjacent
organ organization.
Calcification (short black
arrow in F) and gas (long
black arrow in F) in teratoma
can be seen.

211. Dr Ahmed Esawy
Differential diagnosis

212. Dr Ahmed Esawy
DEFINITION
SINUS:
 Blind track lined by granulation
tissue leading from epithelial
surface down into the tissues.
 Latin: Hollow (or) a bay

213. Dr Ahmed Esawy
.A) sinus and (b) a fistula . Both usually arise from a
preceding abscess . A) this shows that is a blind track ,
in this case a pilonidal sinus with its hairs b) this shows
that a fistula is a track connecting two (epithelial) lined
surfaces .in this case colocutaneous fistula

214. Dr Ahmed Esawy
Sinus pilonidalis
On the left an example of a sinus pilonidalis.
There is a small abscess just above the nates.
There is no relation with the sphincter complex.

215. Dr Ahmed Esawy
Proctitis
On the left images of a patient who presented with anal complaints.
No fistula was seen.
There is, however, a diffuse thickening of the rectal mucosa due to a proctitis.

216. Dr Ahmed Esawy
Abscess in the Ischioanal space
An abscess in the ischioanal space with no connection to the sphincter complex
Ischiorectal space abscess

217. Dr Ahmed Esawy
Hidradenitis suppurativa in a male
patient. Transverse STIRMRimage
(same parameters shows extensive
superficial infection (arrows).
Absence of any infection related to
anal canal and intersphincteric
space meant that diagnosis could
be confidently made preoperatively
by using imaging.