Complex Anal Fistula

A complex anal fistula is one in which simple fistulotomy carries substantial risk of continence impairment or treatment failure.

Complex features include:

• High transsphincteric involvement, generally above approximately 30% of the external sphincter
• Suprasphincteric or extrasphincteric anatomy
• Anterior fistula in a woman
• Multiple or branching tracts
• Recurrent fistula
• Crohn disease
• Radiation
• Pre existing faecal incontinence

The priority is sepsis control followed by a sphincter preserving definitive strategy.

Persistent drainage and recurrent abscesses are typical.

Multiple external openings, previous scars or recurrent swelling suggest branching anatomy.

Assess baseline continence before operating. A technically successful cure that creates permanent incontinence is a poor outcome.

Pelvic MRI: map the primary tract, internal opening, secondary extensions, horseshoe component and occult abscess.

Examination under anaesthesia remains important for final operative assessment.

Drain all sepsis before attempting definitive closure.

Place a loose seton through the primary tract when continuing drainage is necessary.

Do not perform a high fistulotomy through substantial external sphincter.

Common definitive options are:

• LIFT
• Endorectal advancement flap
• Selected fistula tract closure techniques
• Staged reconstruction

LIFT is particularly useful for transsphincteric fistula because the tract is interrupted within the intersphincteric plane without dividing the external sphincter.

Advancement flap is useful for high fistulas, but active proctitis, severe scarring and uncontrolled sepsis reduce success.

Persistent drainage after a sphincter preserving procedure does not automatically justify progressively larger sphincter divisions. Repeat MRI and redefine the anatomy first.