The document discusses locating the internal opening of a fistula in ano. It provides information on the clinical presentation and classifications of fistulas. Methods for locating the internal opening are described, including digital examination, probing, and injecting saline or dye into the external opening. Imaging modalities like MRI and endorectal ultrasound can help identify complex anatomies. The key takeaway is that failure to find the internal opening significantly increases the risk of recurrence after surgery to treat the fistula.

1. da
Finding the Internal Opening
Fistula in Ano
Dr.R.Kannan
Prime Indian Hospitals,
Chennai
Consultant Surgical Gastroenterologist & Proctologist
Laser & Advanced Laparoscopic Surgeon
MS., DNB (SGE)., FACS (USA)., FICS., FAIS., FMAS., FIAGES., FACRSI.,
DMAS(Fr)., E-FIAGES., FALS (UGI)., FALS (HPB)., FALS (Coloerctal).,
Vice President 2021 2023.
The Association of Colon and Rectal Surgeons of India (South Zone).
Executive Committee Member 2022 - 2024.
Association of Surgeons of India, Tamil Nadu Chapter
Vice Chairman 2022 2024.
Association of Surgeons of India, Chennai City Branch
Venu : Hotel Savera, Chennai
Date : 22nd & 23rd July 2023

2. FISTULA-IN-ANO
Abnormal communication between the anal canal and perianal
region presenting with serosanguinous discharge, which may also
contain pus and fecal matter.
• Common in 1 to 8 per 10,000 patients.
• Common in men 2:1 to 7:1
• Common in 3rdand 4th decades.
Definition
Forootan M, Bagheri N, Darvishi M. Chronic constipation: A review of literature. Medicine (Baltimore). 2018;97(20):e10631. Hokkanen
SR, Boxall N, Khalid JM, Bennett D, Patel H. Prevalence of anal fistula in the United Kingdom. World J Clin Cases. 2019;7(14):1795.

3. Risk Factors
• Previous perianal abscess formation (66 to 88 %)
• Diabetes Mellitus
• Tuberculosis
• Crohn's disease
• Immunocompromised pts
(HIV infection, malignancy)
• Complications of anal surgeries
• Actinomycosis
He Z, Du J, Wu K, et al. Formation rate of secondary anal fistula after incision and
drainage of perianal Sepsis and analysis of risk factors. BMC surgery. 2020;20(1):1-7.

4. Park’s Classification
(according to the relationship of primary tract to the anal sphincters)
 Intersphincteric (45%)
 Simple low tract
 High tract
 High tract with rectal opening
 Extra rectal extention
 Trans-sphincteric (40%)
 Uncomplicated
 High tract
 Suprasphincteric
 Uncomplicated
 High tract
 Extrasphincteric
 Secondary to trauma
 Secondary to anorectal disease
 Secondary to pelvic inflammation
Ref: The ASCRS textbook of colon and rectalsurgery
By Bruce G. Wolff, James W. Fleshman, David E. Beck
Classification
Tozer P, Sala S, Cianci V, et al. Fistulotomy in the tertiary setting can
achieve high rates of fistula cure with an acceptable risk of deterioration
in continence. J Gastrointest Surg. 2013;17(11):1960-1965.
20% cannot be classified by the Parks’ classification

5. ASCRS Classifications
1. Simple fistula
- intersphincteric or low transsphincteric fistulas
involving <30% of the external sphincter.
2. Complex fistula
− fistulas with more muscle involvement
− anterior fistulas in female patients
− recurrent fistulas and those associated with
preexisting fecal incontinence
− inflammatory bowel disease or radiation.
Classification
Steele SR, Kumar R, Feingold DL, Rafferty JL, Buie WD; Standards Practice Task Force of the American Society of Colon and Rectal
Surgeons. Practice parameters for the management of perianal abscess and fistula-in-ano. Dis Colon Rectum. 2011;54(12):1465-1474

6. Radiological Classifications
(St. James University Classification)
1. Simple linear intersphincteric fistula (Grade I)
2. Intersphincteric fistula with abscess or secondary
tract (Grade II)
3. Simple trans-sphincteric fistula (Grade III)
4. Trans-sphincteric fistula with abscess or secondary
tract within the ischiorectal fossa (Grade IV)
5. Supralevator and translevator disease (Grade V)
Classification
Morris J, Spencer JA, Ambrose NS. MR imaging classification of perianal fistulas and its implications for patient management. Radiographics. 2000;20(3):623-635.

7. Clinical Presentation
• Perianal discharge
- intermittent or constant, bloody or purulent
• Perianal pain
- worse during defecation, may be constant
• External opening in the perianal region
• Swelling / lump in the perianal area
• Discoloration of skin surrounding the fistula
• Fever

8. Goodsall's Rule
Predict the trajectory of the tract and probable location of the internal
opening, Goodsall's Rule can be applied.
• With the patient in the lithotomy position
– If the external opening anterior to an imaginary line drawn
horizontally through the anal canal, the fistula usually runs directly
into the anal canal.
– If the external opening is posterior to the line, the fistula usually
curves to the posterior midline of the anal canal.

9. Locating
Internal
Opening

10. How to
locate
Internal
Opening on
Examination
• Opening- usually in midline
• Commonly posterior (6’o clock)
• Invariably at dentate line
• Hypertrophied papilla
– Puckering scar, ulcer
– A fibrous pit
– Soft granulation tissue pimple
– An elevation
– Pus discharge
• Cord like fibrosis
from ext - int opening
• Induration on Bimanual Palpation
• Surrounding mucosa immobile

11. Where to look for Internal Opening of Fistula

12. • External Anal sphincter tone
• Tenderness on examination
• Fibrous tract or cord
• Bogginess-any abscess.
• Lateral or posterior induration
Anorectal Examination
suggests deep postanal or ischiorectal extension.
Palpate tract, leads
to internal opening
Palpate level of
induration
Above or below
anorectal ring Palpation will reveal IO
(papilla, puckering, induration)

13. • Not performed as routine
 Primary opening is difficult to identify
 Case of Recurrent
 Multiple fistulae
 Identify secondary tracts
 Missed primary openings
Imaging Studies

14. • Sigmoidoscopy and colonoscopy
(IBD, Neoplasm, associated secondary tracts)
• Fistulography
(unsuspected pathology, planning surgical management and
demonstrating anatomical relationship)
• MRI
(corroborates correct anatomy and impacts the therapeutic decisions
up to 75% of the time)
• CT
(Associated pelvic pathology assessment)
• Perineal & Endoanal USG
(correlation with intraoperative examination is 90% to 94%)
Work Up

15. • Injection of contrast via the
External opening, antero
posterior, lateral and oblique
x-ray images to outline the
course of the fistula tract.
Fistulography
X-ray pelvis with fistulogram (AP view) showing
contrast material in the portal venous circulation
(yellow arrows) due to forceful injection of contrast
material into the fistulous track (white arrow)

16. • It is becoming the study of choice when evaluating complex fistulae
Horse shoe fistula
MRI
Buchanan GN, Halligan S, Bartram CI, Williams AB, Tarroni D, Cohen CRG. Clinical examination, endosonography, and MR imaging in
preoperative assessment of fistula in ano: comparison with outcome-based reference standard. Radiology. 2004;233(3):674-681.

17. Relatively well defined fistulous tract arising in the right
gluteal cleft,coursing antero-superiorly, forming a crescent-
like intersphincteric collection along the proximal anal canal
between 8 to 12O’clock positions with internal opening at 12
O’clock position as described
- St. James University Hospital Classificatio – Grade II.
MRI

18. Extra sphincteric abscess visualized in the perianal region on the
right side extending from 6 to 12 o’clock position. The abscess is
seen piercing the external sphincter at 6 o’clock position to lie in
the intersphincteric plane from 6 to 10 o’clock position. Internal
and external opening not made out.
MRI

19. • A CT scan is more helpful in the
setting of perirectal inflammatory
disease than in the setting of small
fistulae because it is better for
delineating fluid pockets that require
drainage than for small fistulae
CT Scan
CT of acute perianal abscesses and infected fistulae

20. • To define muscular anatomy differentiating
intersphincteric from transsphincteric lesions.
• Determine sphincter integrity
• Complexity of the fistula
Endorectal Ultrasound
Ratto C, Grillo E, Parello A, Costamagna G, Doglietto G. Endoanal ultrasound-guided surgery for anal fistula. Endoscopy. 2005;37(08):722-728.

21. EUS

22. Horse Shoe Fistula

23. Procedures
to locate
Internal
Opening
• From external opening inject
saline, H2O2, betadiene, methylene
blue - locates IO
• Gentle probing of EO
• Metal wire probing
Note- large Sim’s or lighted
proctoscopes block the IO. Use
proctoscope
• Dissect around EO, up to ES giving
traction which shows IO
• Coring /dissection of the tract will
lead to IO
• VAAFT scope light seen just behind
IO

24. Digital palpation
Case 1

25. Traction of the fistula tract

26. Normal Saline Injection

27. Methylene Blue

28. Gentle metal probing

29. Complex fistula
Case 2

31. IO above dentate line

32. Case 3 Traction of the tract

34. IO Probing and wash
Case 4

35. Two Internal Openings
Case 5

36. Synchronous fistula
Two tracts
Case 6 Case 7

37. Case 8 VAAFT

38. • Unidentified IO.
• Relative risk of anal fistula recurrence was 20 fold higher
in patients in whom Internal opening was not identified.
• Complex fistula in Ano.
Factor’s increasing the risk of recurrence

39. • No matter which procedure you have chosen for fistula,
if internal opening is not found then operation is bound
to be a Doomed failure
Take Home Message

40. k