Anal abscesses and anal fistulas are related conditions involving infection and inflammation of the anal glands. They are painful, often recurrent disorders that can significantly affect quality of life if not properly treated.
🔥 1. Anal Abscess
📚 Definition:
An anal abscess is a localized collection of pus in the perianal or perirectal tissues, usually caused by infection of an anal gland.
⚠️ Causes:
- Obstructed anal crypt gland (most common)
- Crohn’s disease
- Trauma
- Immunocompromise (e.g., diabetes, HIV)
- Sexually transmitted infections
😖 Symptoms:
- Severe pain near the anus, worse with sitting or defecation
- Swelling, redness, warmth near anus
- Fever, malaise (in deeper abscesses)
- Possible drainage of pus
🔍 Diagnosis:
- Clinical exam is usually sufficient
- Digital rectal exam (DRE) may reveal tenderness
- Imaging (CT or MRI) for deep, non-visible abscesses
💊 Treatment:
- Prompt surgical drainage is the definitive treatment (I&D)
- Antibiotics may be used in addition to drainage if:
- Immunosuppressed
- Extensive cellulitis
- Fever or systemic symptoms
🔁 2. Anal Fistula (Fistula-in-Ano)
📚 Definition:
An anal fistula is an abnormal tract between the anal canal and the perianal skin, often developing after an abscess has drained or been surgically treated.
📈 Classification (by relation to sphincter muscles):
| Type | Description |
|---|---|
| Intersphincteric | Between internal and external sphincter |
| Transsphincteric | Through both sphincters |
| Suprasphincteric | Arches above external sphincter |
| Extrasphincteric | From rectum to skin, bypassing sphincters |
😖 Symptoms:
- Persistent painless drainage from a skin opening near anus
- Recurrent abscesses
- Pain, swelling, or skin irritation
- External opening may be visible
🧪 Diagnosis:
- Clinical examination
- Probe test in the OR
- MRI pelvis: best for complex or recurrent fistulas
- Endoanal ultrasound (alternative)
💊 Treatment
🔹 Anal Abscess
- Incision and drainage (under local or general anesthesia)
🔹 Anal Fistula
- Fistulotomy (for simple, low fistulas): tract is opened and allowed to heal flat
- Seton placement: for complex/high fistulas, maintains drainage without cutting the sphincter
- Advancement flap, LIFT procedure, or fibrin glue/plug: options for sphincter-preserving surgery
- Treat underlying conditions (e.g., Crohn’s)
❗ Complications
- Fecal incontinence (especially if sphincter is injured during surgery)
- Recurrence
- Chronic pain or drainage
- Sepsis if abscess is untreated
✅ Summary
| Condition | Abscess | Fistula |
|---|---|---|
| Cause | Anal gland infection | Chronic tract after abscess |
| Symptoms | Pain, swelling, fever | Persistent drainage, recurrent abscess |
| Diagnosis | Clinical, imaging if needed | Clinical, MRI for complex fistulas |
| Treatment | Surgical drainage ± antibiotics | Surgical repair (fistulotomy, seton, etc) |