1. Dr Ayed Haddad Consultant Colorectal & General Surgeon
ANORECTAL FISTULA
Dr Ayed Haddad
Consultant Colorectal & General Surgeon

2. Definition
Fistula = an abnormal communication between any two epithelium-lined surfaces (Latin - a pipe or a reed)
Fistula-in-ano = a granulating track between the anorectum and the perineum

3. Etiology 1- Anal gland theory
The majority of fistulas are secondary to cyproglandular infection (of anal glands)
chronic intersphincteric abscess in > 90%
small abscesses may burst into the anal canal - patient unaware
drained or spontaneously discharged abscess forms a potential fistula. If the track becomes epithelialized the fistula persists.

4. Spread of anal gland infection

5. 2- Congenital fistulas
If occur during infancy
If the track is lined by columnar or transitional epithelium.
Intersphincteric, retrorectal or pelvic dermoid – if burst with secondary infection.
A remnant of the medullary canal in spina bifida - at birth & disharge CSF.
Sacrococygeal teratoma or dermoid cyst – infected.
Imperforated anus, anorectal agenesis.
Non-communicating meningocele – adults.
Rectal duplication

6. Appendicitis, salpingitis, diverticular disease, IBD, pelvic neoplasm.
3- Pelvic sepsis
Appendicitis, salpingitis, diverticular disease, IBD, pelvic neoplasm.
Pelvic sepsis
Supralevator abscess
Intersphincteric spread
Bursts through levator ani
Perianal abscess
Ischiorectal abscess
High intersphincteric fistula
Extrasphincteric fistula

7. 4- Perineal injuries
Penetrating perineal injuries
Blunt trauma
Ingested foreign bodies - fish or chicken bones
Impalement injury - falling astride a sharp object or RTA
Always consider a coexisting urethral injury

8. 5- Anal disorders
Fissure - short & superficial ; running from the base of the fissure to the hypertrophied anal papilla; almost always midline.
Hidradentitis – superficial; submucous or subcutaneous; multiple & high anal fistulas = follicular occlusum tetrad (pyoderma fistulans).
Hemorrhoids Sepsis complicating a thrombosed perianal venous plexus  subcutaneous or submucous fistula.
Operations for anal disease - chronic infective process  fistula; sclerotherapy for hemorrhoids, internal sphincterotomy, closed hemorrhoidectomy.

9. 6- Inflammatory bowel disease
Crohn's disease: Typical features - recurrent abscess, fistulas, skin tags, ulcers & strictures.
 Minimal symptoms Multiple with high blind tracks and the internal opening is above the anorectal ring. High proportion of extrasphincteric & high trans- sphincteric fistulas More common in large bowel disease, esp. with rectal involvement
Ulcerative colitis Fistulas, fissures, abscesses.

10. 7- Tuberculosis No specific clinical features
Dx – suspicion; histopathology (epitheloid giant cells - more reliable than acid-fast bacilli); Mantoux reaction is almost always positive ; CXR – normal / healed focus
8- Actinomycosis
Indurated perineum with multiple fistulas

11. 9- Sexually transmitted diseases
AIDS, syphilis and lymphogranuloma venereum  perianal sepsis  fistula.
An incidental finding
10- Malignancy
First presenting feature of an underlying anorectal tumor - squamous cloacogenic adenocarcinoma & anal glandular malignancy.
Malignancy may arise in chronic fistula-in-ano

12. INCIDENCE General population = 0.8% (US) Overall admissions = 0.6%.
Colorectal units = 10%
Male-female ratio = 4.6 : 1
Age = 3rd-4th decade; uncommon > 60 yrs

13. CLASSIFICATION
Low F = that open into the anal canal at the level of the pectinate line. Subdivided into submucous, subcutaneous or trans-sphincteric.
High F = that open above the pectinate line.
Simple F = low F, involve <25% of the circumference of the anorectum.
Complex F = high F or those that involve at least 75% of the circumference of the anorectum.
Intersphincteric Trans-sphincteric Extrasphincteric Suprasphincteric

14. Any classification should consider both the position of the primary track, in the vertical & horizontal planes, & the secondary track (or extension), also in both planes.
Horizontal tracks
Goodsall's rule = fistulas that have an external opening above a horizontal line drawn transversely across the midpoint of the anus in the lithotomy position (Figure 16.90) drain directly into the anus at the dentate line. Fistulas with external opening below this line take a curved course to drain into the midline posteriorly.

16. Exception:
☺Only 49% of anterior F obey the rule (90% of the posterior F)
☺Very low posterior F, may follow a direct course
☺Anterior horseshoe fistulas occur despite the rule & in all the F, the external opening lay > cm from the anal verge
☺Posterior horseshoe F are often associated with numerous external openings.

17. Circumferential spread must take into consideration the sites of the internal & external opening & the plane of the spread (intersphincteric, ischiorectal or supralevator).
Most common in the ischiorectal fossa secondary to trans-sphincteric F In intersphincteric plane may be associated with all types of fistula
Least common in suprasphincteric or extrasphincteric F.

18. The distribution of the internal opening

19. Subdivisions of fistula
Vertical tracks
Intersphincteric Trans-sphincteric Suprasphincteric Extrasphincteric
Subdivisions of fistula
 direction of the primary track (up or down)
presence or absence of a secondary track
direction of the secondary track (up or down)
if the primary or secondary track ends blindly or associated with an abscess

20. Intersphincteric fistula
(a) Simple = internal opening at the dentate line, and the external opening in the perianal region.
(b) Simple fistula with a small perianal abscess and a closed external opening.

21. (c) High blind track – a secondary track runs upwards in the intersphincteric plane to the pararectal region but dos not enter the rectum and is not associated with an abscess.
(d) High track entering the rectum – a secondary track extends upwards in the intersphincteric plane and enters the rectum.

22. (e) High track & a supralevator abscess – the secondary track passes upwards & ends in a supralevator abscess (f) High blind track & supralevator abscess without a perianal opening.

23. (g) High track entering the rectum without a perianal opening.

24. Trans-sphincteric fistula
Simple:
1- Low TS = the track pierces the lower fibers of the external sphincter at the point where one of the fibrous septa transverses the muscle.

25. Simple:
2- Mid TS = the track follows one of the venous channels directly through the external sphincter opposite its internal opening at the pectinate line to enter the ischiorectal fossa discharging into the buttock.

26. Simple:
3- High TS = the track pierces the external sphincter close to the anorectal ring before it enters the ischiorectal fossa and the perineum

27. (b) Without perianal opening and recurrent abscess.
(c) High blind track – the secondary track runs upwards high in the ischiorectal fossa. The secondary track may be caused iatrogenic or inadequately drained ischiorectal abscess.

28. (d) High blind track with a supralevator abscess – the secondary track runs upwards to end into a supralevator abscess.

29. Suprasphincteric fistula
(a) Simple= The fistula track starts in the intersphincteric plane and loops over the puborectalis and external sphincter complex to discharge into the perineum.
(b) With supralevator extension and abscess.

30. Extrasphincteric fistula
The majority are iatrogenic:
over-enthusiastic drainage of an ischiorectal abscess, resulting in rectal wall perforation
rectal injuries (trauma or iatrogenic)
drainage of a supralevator abscess secondary to a trans-sphincteric fistula into the rectum
passage of a probe through a high secondary track complicating a trans-sphincteric fistula
The other cause is a pelvic abscess which has penetrated the pelvic diaphragm and discharge through the buttock (common in Crohn's disease, > rectal or gynecological disease, penetrating injuries).

32. Incidence of fistulas
IS = 70%
TS = 23%
SS = 5%
ES = 2%

33. Clinical Presentation
Anal discharge preceded by episodes of pain and perianal swelling that either spontaneously discharges or requires surgical drainage. .
H/O repeated episodes of perianal sepsis (1-3 episodes ≈ 100%).
Bleeding (12%)
Associated fissure-in-ano in 14%, hemorrhoids.
H/O pruritus ani
Symptoms related to underlying disease

34. Assessment Clinical assessment Inspection:
External opening (No, site, distance from anal verge, material discharged,..); No opening in 16% Perianal excoriation, ulcerations Scars
Palpation:
Track - characteristic induration and discharge of pus at the external opening
Chronic perianal or ischiorectal abscess
Fibrosis, scarring

35. PR:
Induration of the fistula track
Internal opening – fibrosis at opening
Intersphincteric or supralevator abscess
Fibrotic stricture at the anorectal ring
Gutter deformity from previous surgeries
Tone of the internal anal sphincter and the contractile potential of the external sphincter and puborectalis
The accuracy of digital assessment in determining the type of the primary track is 70-85%.

36. Ano-procto-sigmoioscopy:
Internal opening - characteristic bead of pus emerging from it
Internal opening may by defined by grasping the external opening with a pair of tissue forceps and applying traction to it.
Inflammatory bowel disease, TB (esp. in recurrent fistula) – Bx
EUA
It is essential for proper evaluation of the fistula & sphincter anatomy.
Examination in OPC is suboptimal – painful, probing is CI, deformed anatomy,..
A light GA without muscle relaxant is preferred

37. Manometry. Is not generally required,
Manometry Is not generally required, Useful for planning the operative approach Indications: -women with previous obstetric trauma
- previous surgeries elderly
- soiling / incontinence
- Crohn's disease or AIDS recurrent fistula.

38. Fistulography
Usually not indicated (recurrent F, Crohn’s disease – altered anorectal anatomy)
Why: - poor identification of secondary tracts
- difficult to distinguish between an abscess located high in the ischioanal fossa & in the supralevator space
- Difficult to determine the level of the internal opening
- Accuracy rates in identifying the internal opening & extensions is 16%
- False-positive rate of 12% (5% for internal opening)
- Dissemination of sepsis

39. Endoanal and intrarectal ultrasonoraphy:
U/S can identify: - internal opening
- primary tracts & their relation to sphincters
- intersphincteric sepsis
- some tran-sphincteric F
- defects in sphincter
Drawbacks: - poor anatomical definition beyond the internal sphincter
- Can not detect primary superficial, extra- sphincteric & suprasphincteric tracts or secondary supralevator or infralevator tracts
-Gives more information about the sphincter than the anatomy of the fistula
-Overdiagnose the intersphincteric collections

40. Magnetic resonance imaging
It is the investigation of choice to define complex anorectal sepsis and fistulas.
Identify the: - presence of fistula and the extension
- anatomy of the primary track
- sepsis without fistulas
- scar tissue alone (prevent unnecessary op)
- blind tracks with no internal opening (prevent unnecessary op)
horseshoe fistulas
- differentiation between supra- & infra- levator sepsis
It identifies the anatomy of the fistula (U/S identifies the anatomy of the sphincter)

41. Thank You