Anal fistula

Anal fistula

Different types of anal fistula
Classification and external resources
Specialty General surgery
ICD-10 K60.3
ICD-9-CM 565.1
eMedicine med/2710
Patient UK Anal fistula

Anal fistula (plural fistulae), or fistula-in-ano, is a chronic abnormal communication between the epithelialised surface of the anal canal and (usually) the perianal skin.[1] An anal fistula can be described as a narrow tunnel with its internal opening in the anal canal and its external opening in the skin near the anus.[2] Anal fistulae commonly occur in people with a history of anal abscesses. They can form when anal abscesses do not heal properly.[3]

Anal fistulae originate from the anal glands, which are located between the internal and external anal sphincter and drain into the anal canal.[4] If the outlet of these glands becomes blocked, an abscess can form which can eventually extend to the skin surface. The tract formed by this process is a fistula.[1]

Abscesses can recur if the fistula seals over, allowing the accumulation of pus. It can then extends to the surface again - repeating the process.[1]

Anal fistulae per se do not generally harm, but can be very painful, and can be irritating because of the drainage of pus (it is also possible for formed stools to be passed through the fistula). Additionally, recurrent abscesses may lead to significant short term morbidity from pain and, importantly, create a starting point for systemic infection.[1]

Treatment, in the form of surgery, is considered essential to allow drainage and prevent infection. Repair of the fistula itself is considered an elective procedure which many patients opt for due to the discomfort and inconvenience associated with an actively draining fistula.[1][3]


Depending on their relationship with the internal and external sphincter muscles, fistulae are classified into five types:

Signs and symptoms

Anal fistulae can present with the following symptoms:[4]

  • pain
  • swelling
  • tenderness
  • fever


Diagnosis is by examination, either in an outpatient setting or under anaesthesia (referred to as EUA — Examination Under Anaesthesia). The fistula may be explored by using a fistula probe (a narrow instrument). In this way, it may be possible to find both openings. The examination can be an anoscopy. Diagnosis may be aided by performing a fistulogram, proctoscopy and/or sigmoidoscopy.

Possible findings:

Differential diagnosis

Other conditions in which infected perianal "holes" or openings may appear include Pilonidal cysts/sinuses.


There are several stages to treating an anal fistula:

Definitive treatment of a fistula aims to stop it recurring. Treatment depends on where the fistula lies, and which parts of the internal and external anal sphincters it crosses.

There are several options:

Anal fistula after surgical treatment
Japan: A man with an anal fistula. From the Yamai no Soshi, late 12th century.


Some people will have active infection when they present with a fistula, and this requires clearing up before definitive treatment can be decided.

Antibiotics can be used as with other infections, but the best way of healing infection is to prevent the buildup of pus in the fistula, which leads to abscess formation. This can be done with a seton.


  1. 1 2 3 4 5 "Anorectal Fistula". MERCK MANUAL Consumer Version. Retrieved 2016-06-27.
  2. 1 2 "Anorectal sinuses and fistulae". Retrieved 2016-07-03.
  3. 1 2 3 4 5 6 "Colorectal Surgery - Anal Fistula". Retrieved 2016-07-03.
  4. 1 2 Mappes, H. J.; Farthmann, E. H. (2001-01-01). Anal abscess and fistula. Zuckschwerdt.
  5. 1 2 3 4 Parks, A. G.; Gordon, P. H.; Hardcastle, J. D. (1976-01-01). "A classification of fistula-in-ano". The British Journal of Surgery. 63 (1): 1–12. doi:10.1002/bjs.1800630102. ISSN 0007-1323. PMID 1267867.
  6. 1 2 3 4 5 Shawki, Sherief; Wexner, Steven D (2011-07-28). "Idiopathic fistula-in-ano". World Journal of Gastroenterology : WJG. 17 (28): 3277–3285. doi:10.3748/wjg.v17.i28.3277. ISSN 1007-9327. PMC 3160530Freely accessible. PMID 21876614.
  7. Hippocrates, "On Fistulae", translation by Francis Adams, Internet Classics Archive, Massachusetts Institute of Technology.
  8. Garg P, Song J, Bhatia A, Kalia H, Menon GR (October 2010). "The efficacy of anal fistula plug in fistula-in-ano: a systematic review". Colorectal Dis. 12 (10): 965–70. doi:10.1111/j.1463-1318.2009.01933.x. PMID 19438881.
  9. Rojanasakul A (September 2009). "LIFT procedure: a simplified technique for fistula-in-ano". Tech Coloproctol. 13 (3): 237–40. doi:10.1007/s10151-009-0522-2. PMID 19636496.
  10. Rojanasakul A, Pattanaarun J, Sahakitrungruang C, Tantiphlachiva K (March 2007). "Total anal sphincter saving technique for fistula-in-ano; the ligation of intersphincteric fistula tract". J Med Assoc Thai. 90 (3): 581–6. PMID 17427539.
  11. van Onkelen, RS; Gosselink, MP; Schouten, WR (February 2012). "Is it possible to improve the outcome of transanal advancement flap repair for high transsphincteric fistulas by additional ligation of the intersphincteric fistula tract?". Diseases of the colon and rectum. 55 (2): 163–6. doi:10.1097/DCR.0b013e31823c0f74. PMID 22228159.
  12. Prosst RL, Herold A, Joos AK, Bussen D, Wehrmann M, Gottwald T, Schurr MO (September 2012). "The anal fistula claw: the OTSC clip for anal fistula closure". Colorectal Dis. 14 (9): 1112–7. doi:10.1111/j.1463-1318.2011.02902.x. PMID 22122680.
  13. Prosst RL, Ehni W (July 2012). "The OTSC Proctology clip system for anorectal fistula closure: the 'anal fistula claw': case report". Minim Invasive Ther Allied Technol. 21 (4): 307–12. doi:10.3109/13645706.2012.692690. PMID 22657572.
  14. Prosst RL, Ehni W, Joos AK (September 2013). "The OTSC Proctology clip system for anal fistula closure: first prospective clinical data". Minim Invasive Ther Allied Technol. 22 (5): 255–9. doi:10.3109/13645706.2013.826675. PMID 23971828.
  15. Mennigen R, Laukötter M, Senninger N, Rijcken E (April 2015). "The OTSC(®) proctology clip system for the closure of refractory anal fistulas". Tech Coloproctol. 19 (4): 241–6. doi:10.1007/s10151-015-1284-7. PMID 25715788.
  16. Garg P, Garg M (7 April 2015). "PERFACT procedure: a new concept to treat highly complex anal fistula". World J Gastro. 21 (13): 4020–9. doi:10.3748/wjg.v21.i13.4020. PMID 25852290.
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