Fistulo in Ano
🩺 Fistula-in-Ano: Symptoms and Signs
- 📜 History of perianal abscess - either drained spontaneously or surgically.
- 💧 Persistent or intermittent discharge of pus, mucus, blood, or faecal matter → often causes perianal irritation, itching, and discomfort.
- 🔄 Intermittent course: Periods of healing followed by recurrent opening of the fistula.
- 👁️ Typically a single external opening near the anal verge; occasionally multiple openings may be present.
- ✋ On digital rectal exam (PR): indurated tract may be palpable; applying pressure may produce discharge.
- 🔦 Proctoscopy/sigmoidoscopy can help define the internal opening and exclude associated pathology (Crohn’s, carcinoma).
- ⚠️ Chronic cases may cause excoriation, perianal skin maceration, and foul odour due to continuous leakage.
🧪 Investigations
- 📸 Fistulogram: Contrast study to outline tract (less commonly used now).
- 🔊 Endoanal ultrasound: Helpful for assessing sphincter involvement.
- 🧲 MRI pelvis: Gold standard for complex or recurrent fistulae; maps tract anatomy and relationship to sphincter muscles.
- 🧫 Examination under anaesthesia (EUA): Often both diagnostic and therapeutic; allows accurate probing of the fistula tract.
🔍 Differential Diagnosis
- 🌀 Pilonidal sinus (usually midline and higher in sacrococcygeal region).
- 🔥 Hidradenitis suppurativa (multiple painful nodules/abscesses in groin or perianal area).
- 💧 Incontinence-related skin changes.
- 🌿 Crohn's disease (multiple, branching, complex fistulae are common).
- ⚠️ Trauma or iatrogenic fistula (post-surgical or obstetric injury).
🛠️ Treatment
- 🔍 Identification of tract by probing under GA, then fistulotomy (lay open) → allows healing by granulation from the base. Success rate is high for simple fistulae.
- ⚠️ High fistulae (crossing puborectalis or involving sphincter muscles): risk of faecal incontinence if divided. Require specialist management.
- 🪢 Seton placement (silk/elastic thread placed in tract): used for complex or high fistulae to allow drainage and fibrosis while preserving sphincter integrity.
- 🏥 Two-stage operations may be required to reduce incontinence risk (e.g., staged fistulotomy or advancement flap procedures).
- 💡 Adjuncts: Fibrin glue, bioprosthetic plugs, and LIFT (ligation of intersphincteric fistula tract) are sphincter-preserving alternatives, though recurrence rates vary.
- 🌿 Crohn’s-associated fistulae → often require combined medical (biologics such as infliximab) and surgical approaches.
💡 Clinical Pearl: In UK practice, most simple low fistulae are treated by fistulotomy. For high/complex tracts, the goal is balance - eradicate sepsis while preserving continence. Always assess for underlying Crohn’s disease if multiple tracts or recurrent presentations.
