Abnormal track between anal canal/rectum and perianal skin, usually arising from cryptoglandular abscess.
History taking
- • Recurrent perianal discharge, swelling, pain; prior abscess drainage
- • Pruritus, bleeding, soiling
- • Crohn disease, TB, malignancy, prior surgery, radiation
Examination
- • External opening(s), induration, Goodsall's rule for internal opening prediction
- • PR exam: internal opening, induration along track
Red flags
- • Multiple openings, horseshoe fistula, anorectal stricture
- • Suspect Crohn, TB, HIV — atypical or complex
Differential diagnosis
- • Pilonidal sinus, hidradenitis suppurativa, perianal Crohn, anorectal abscess
Recommended investigations
- • MRI pelvis for complex/recurrent fistula
- • EUA with probing under anaesthesia
- • Colonoscopy if Crohn suspected; CBC, ESR, HIV test
Diagnosis
- • Clinical + MRI/EUA; classify by Parks (intersphincteric, transsphincteric, suprasphincteric, extrasphincteric)
Initial treatment / management
- • Surgical: fistulotomy for simple low fistula; seton for high/complex
- • Specialised: LIFT, advanced flap, fibrin glue, plug for complex
- • Treat underlying Crohn/TB
Prescription examples
- • Post-op: sitz baths, stool softeners, analgesics
- • Antibiotic only if cellulitis or in specific procedures
Follow-up advice
- • Regular sitz baths and dressings; review weekly until healed
- • Recurrence rate higher with complex fistulas
Patient counselling
- • Hygiene, sitz baths, healthy diet
- • Long healing time, possible recurrence
Referral criteria
- • All fistulas to colorectal surgery
- • Suspected IBD to gastroenterology
Clinical pearls
- • Goodsall's rule guides internal opening location
- • Never aggressively divide sphincter in anterior fistula in females — incontinence
References
- • ASCRS Clinical Practice Guidelines for Anorectal Abscess and Fistula 2022
Educational outpatient guide — verify against local guidelines before clinical use.
