An anal fistula is one of the most misunderstood — and most dreaded — conditions in proctology. Many patients suffer for months or even years with persistent discharge, pain, and embarrassment before seeking help. The good news: modern treatments are minimally invasive, highly effective, and can resolve fistulas permanently.
Let's understand the anal fistula causes symptoms, how they develop, and what your treatment options look like in 2026.
What Exactly Is an Anal Fistula?
A fistula is an abnormal tunnel that connects the inside of the anal canal to the skin near the anus. Imagine a small passageway — with an internal opening inside the rectum and an external opening on the skin around the anus.
This tunnel doesn't belong there. It forms as a consequence of infection, and once formed, it rarely closes on its own because the passage is constantly exposed to stool, bacteria, and moisture.
What Causes Anal Fistula? (The Abscess Connection)
Understanding anal fistula causes symptoms starts with understanding perianal abscesses — because 90% of fistulas begin as an abscess.
Here's how it happens, step by step:
- Infection begins: Small glands inside the anal canal (called anal crypts) get blocked. Bacteria accumulate and an infection develops.
- Abscess forms: The infection creates a pocket of pus — a perianal abscess. This causes severe pain, swelling, and often fever.
- Abscess drains: The abscess either bursts on its own or is surgically drained. You feel instant relief.
- Tunnel persists: In about 30–50% of cases, the drainage path doesn't heal. The tunnel becomes lined with tissue (epithelialisation), and a permanent fistula forms.
Other Causes of Anal Fistula
While perianal abscesses cause most fistulas, other conditions can also lead to fistula formation:
- Crohn's Disease: An inflammatory bowel disease that can cause fistulas anywhere in the digestive tract. Up to 30% of Crohn's patients develop perianal fistulas.
- Tuberculosis: TB-related fistulas are more common in India than in Western countries. They require anti-TB treatment alongside surgical management.
- Radiation therapy: Patients who have received pelvic radiation (for cervical, rectal, or prostate cancer) can develop radiation-induced fistulas.
- Trauma or surgery: Previous anorectal surgeries or obstetric injuries (during complicated childbirth) can occasionally lead to fistula formation.
- Sexually transmitted infections: Rarely, infections like lymphogranuloma venereum can cause perianal fistulas.
Symptoms of Anal Fistula — How to Recognise It
The anal fistula causes symptoms that are quite distinct from piles or fissures. Here's what to watch for:
- Persistent discharge: Pus, blood, or mucus leaking from a small opening near the anus. This is the hallmark symptom — you may notice staining on your underwear.
- Recurring pain: Dull, throbbing pain around the anus that worsens when sitting, coughing, or during bowel movements.
- Swelling and redness: A tender lump near the anus that may periodically fill with pus and then drain.
- Fever and chills: When the fistula tract gets blocked and a fresh abscess forms, you may develop fever.
- Skin irritation: Chronic discharge causes the surrounding skin to become raw, itchy, and macerated.
- History of abscess: If you've had a perianal abscess drained in the past and now have persistent discharge, a fistula is very likely.
Types of Anal Fistulas (Parks Classification)
Your surgeon classifies your fistula based on its relationship to the sphincter muscles. This classification determines which surgery is appropriate:
| Type | Path | % of Cases | Complexity |
|---|---|---|---|
| Inter-sphincteric | Between internal and external sphincter | 45% | Simple |
| Trans-sphincteric | Crosses through external sphincter | 30% | Moderate |
| Supra-sphincteric | Loops over the top of the sphincter | 20% | Complex |
| Extra-sphincteric | Bypasses the sphincter entirely | 5% | Very complex |
How Is a Fistula Diagnosed?
An experienced proctologist can often diagnose a fistula through physical examination alone. However, imaging is crucial for planning surgery:
- Digital rectal examination: The surgeon feels for the internal opening and the fistula tract.
- Proctoscopy: A short, lubricated scope is inserted to visualise the internal opening.
- MRI Fistulography: The gold standard. An MRI maps the exact course of the fistula, identifies branches, and shows the relationship to the sphincter muscles. This is essential before any surgery.
- Endoanal ultrasound: An alternative to MRI in some centres, though MRI is generally preferred.
Treatment Options for Anal Fistula
Unlike piles or fissures, fistulas almost never heal on their own. Surgery is the definitive treatment. The choice of procedure depends on fistula type and complexity:
- Fistulotomy: The tract is laid open and allowed to heal from inside out. Best for simple, low fistulas. Cure rate: 90–95%.
- Laser FiLaC: A laser fibre is inserted into the tract and the tunnel is destroyed from inside. Sphincter-sparing, minimal pain. Cure rate: 85–90%.
- LIFT Procedure: The tract is tied off between the two sphincter muscles. Good for inter-sphincteric fistulas. Cure rate: 75–85%.
- VAAFT: A tiny camera is inserted into the tract to directly visualise and treat it. Excellent for recurrent cases.
- Seton Placement: A thread is placed through the tract to promote controlled drainage and fibrosis. Used for complex, high fistulas in a staged approach.
If you've noticed persistent discharge, recurrent swelling, or have a history of perianal abscess, don't wait for it to get worse. SURGISAATHI offers free, confidential consultations with experienced proctologists who specialise in modern fistula treatments. Book your consultation today — the sooner a fistula is treated, the simpler the surgery.