Anal Fistula

FISTULA IN ANO (ANAL FISTULA)

An anal fistula is an abnormal channel between the anal canal (back passage) and the skin around the anal opening. It is associated with an abscess formation around the anus and is more common in men.

Aetiology and Risk Factors

The formation of an anal fistula typically occurs as a result of an anal abscess. About 25-50% of people with an anal abscess will develop an anal fistula. In rare cases, anorectal cancer can occasionally present with an anal fistula.

Another risk factors include:

  • Inflammatory bowel disease including Crohn’s disease and ulcerative colitis
  • Systemic diseases like tuberculosis, diabetes and HIV
  • Past trauma to the anal region
  • Past radiation therapy to the anal region

Clinical Features:

Anal fistula commonly occur in cases of chronic anal infection (e.g. anal abscess). They often present with an intermittent or continuous discharge of pus, mucus (slime) or blood on the skin around the anus.

Fistulas may also cause severe pain, swelling, change in bowel habit and systemic features of infection like fever, malaise, weakness.

On examination, an external opening on the skin may be seen; these can be fully open or covered in granulation tissue. A fibrous tract might be felt below the skin on digital rectal examination.

Bariatric Treatment in Pune

Investigations:

  • Rigid sigmoidoscopy can be used to visualize the opening of the tract in the anal canal. Further investigations, such as
  • MRI imaging,
  • Fistulography
  • Endo-anal ultrasound may be used to visualize the remaining part of the tract.

Based on Park’s classification system, there are four types of anal fistulae (Fig):

  • Inter-sphincteric fistula (most common)
  • Trans-sphincteric fistula
  • Supra-sphincteric fistula (least common)
  • Extra-sphincteric fistula

Fistula Treatment:

conservative approach can be used in case patient has no symptoms. Various surgical options are available for those deemed not suitable for conservative approach.

Surgical Treatment:

Surgical treatment depends on the Type and Level of Fistula

  • Fistulotomy involves laying open of the tract and allowing it to heal by secondary intention. A probe is passed into the tract and the skin, subcutaneous tissue, and internal sphincter are divided in turn, thus opening the tract.
  • Placement of a seton (Silk or Nylon) : Pass the seton through the fistula tract around the deep external sphincter after opening the skin, subcutaneous tissue, internal sphincter muscle, and subcutaneous external sphincter muscle. The seton is tightened down and secured with a separate silk tie.

With time, fibrosis occurs above the seton as it gradually cuts through the sphincter muscles and essentially exteriorizes the tract. The seton is tightened on subsequent office visits until it is pulled through over 6-8 weeks. Also it is possible to use cutting seton without associated fistulotomy.

  • Other Treatments: Mucosal Advancement Flap, LIFT Procedure, Diversion.

Complications:

Delayed postoperative complications may include the following:

  • Recurrence: Standard fistulotomy – The reported rate of recurrence is 0-18%, Seton use – The reported rate of recurrence is 0-17%,
  • Incontinence (stool)
  • Anal stenosis – The curing process causes fibrosis of the anal canal; bulking agents for stool helps to prevent narrowing
  • Delayed wound healing – Usually healing process takes 12 weeks unless an underlying disease process is present (i.e, recurrence, Crohn disease)

Complications:

Delayed postoperative complications may include the following:

  • Recurrence: Standard fistulotomy – The reported rate of recurrence is 0-18%, Seton use – The reported rate of recurrence is 0-17%,

  • Incontinence (stool)

  • Anal stenosis – The healing process causes fibrosis of the anal canal; bulking agents for stool help to prevent narrowing

  • Delayed wound healing – Complete healing occurs by 12 weeks unless an underlying disease process is present (ie, recurrence, Crohn disease)