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Anal Fistula


An anal fistula is an abnormal communication between the anal canal / lower rectum and the perineal, perianal or buttock skin

Anal Fistula

A fistula is usually identified by the external opening (often a small raised hole lined with granulation tissue and leaking blood or pus). Occasionally a faecal discharge will be present.

Rectal examination should be performed to exclude anal canal or low rectal malignancy.

If systemically well urgent referral is not required.

Loose stools or bloody stools raised the possibility of IBD (Crohn’s).

In females, the passage of flatus or faecal material from the vagina is diagnostic of a recto-vaginal fistula and requires urgent referral, particularly if there is recent obstetric history.

The fistula track may be palpable heading towards the anal canal, but not in all cases, and the internal opening is rarely palpable.

Most fistulas are a result of anal sepsis (anal gland infection).

The following should be referred as a possible fistula;

  • I&D of abscess >8 weeks before and not healing
  • Infection at the site of a previous I&D
  • Recurrent peri-anal abscesses at the same site
Conservative management

Most anal fistulas do not require urgent treatment.

A short course of antibiotics (gram negative cover) may be enough to settle acute symptoms.

If a further abscess develops then manage as for primary anal sepsis (Surgical Assessment Unit SAU abscess pathway).

Initial conservative surgical management may consist of a loose seton suture. This is a ring of silicone or braided nylon (Ethibond) that is passed through the anal canal and the fistula track. This marks the track for further investigation and allows continuous drainage (to prevent a further abscess).

Surgical management

There are a range of surgical treatment options with varying risks and success.

In general, the better the chance of achieving cure, the higher the risk of damage to the sphincter complex, with subsequent incontinence.

Treatments have to be tailored to fistula anatomy and sphincter reserve, as well as to the wishes, expectations and lifestyle of the patient.

For some patients the loose seton is a permanent way to manage a fistula, and is generally tolerated well in the long term.

If a seton falls out then a referral back to the colorectal surgeon is required (often a phone call to the secretary may get this sorted quicker).

Unless the patient is unwell this is generally not urgent.


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