At a glance
An anal fistula is an abnormal tunnel that connects the inside of the anal canal to the skin near the anus. It usually develops after an abscess (a collection of pus from infection) in one of the small glands just inside the anus.
If you have just been told you have a fistula, this guide explains what that means in plain terms.
How it forms
The most common pathway:
- An anal gland becomes infected. Small glands sit just inside the anal canal. When one becomes blocked, bacteria can multiply and cause an abscess.
- An abscess develops. This is a painful collection of pus. It may drain on its own or require surgical drainage.
- A tunnel forms. As the abscess drains, it can create a tract — a channel from the gland inside the canal to an opening on the skin outside. This tract is the fistula.
Not every abscess leads to a fistula, but the connection between the two is well established. If you have had a perianal abscess, there is a meaningful chance a fistula will develop.
What it looks and feels like
People with fistulas commonly describe:
- A small opening on the skin near the anus that may ooze fluid or pus
- Persistent discharge — often the most bothersome day-to-day symptom
- Intermittent swelling and pain — particularly if the external opening becomes blocked and the tract fills with fluid
- Recurring abscesses in the same area — a fistula can act as a pathway for repeated infections
- Itching or irritation around the external opening
Some fistulas cause minimal symptoms. Others cause significant daily discomfort. The variability is wide.
Types of fistula
Fistulas are categorised based on their relationship to the sphincter muscles:
- Simple fistulas — a straightforward tract that involves minimal sphincter muscle. These are typically easier to treat.
- Complex fistulas — tracts that involve a significant portion of the sphincter, have multiple branches, or are associated with conditions like Crohn’s disease. These require more careful surgical planning.
Our guide on types of anal fistula covers this in more detail.
Diagnosis
Fistulas are usually diagnosed through:
- Physical examination — the external opening may be visible, and the tract may be felt
- Anoscopy or proctoscopy — a brief look inside the anal canal
- MRI — often used for complex fistulas to map the tract and its relationship to the sphincter muscles
- Endoanal ultrasound — another imaging option used in some centres
Understanding the anatomy of the fistula — where it starts, where it goes, and what it involves — is essential for planning treatment.
Treatment
Why surgery is usually needed
The tract of a fistula is lined with tissue that prevents it from closing on its own. Without treatment, the fistula typically persists, causing ongoing discharge and recurring infections. Surgery aims to eliminate the tract while preserving as much sphincter function as possible.
Common surgical approaches
Fistulotomy — for simple fistulas. The tract is laid open so it can heal from the bottom up. This is the most straightforward approach and has high success rates.
Seton placement — a thread or loop is placed through the fistula tract. It can serve as a drain (keeping infection under control) or as a gradual cutting device. Setons are often used as a first step for complex fistulas.
Advancement flap — tissue is used to cover the internal opening of the fistula. Used for complex fistulas where other approaches might risk sphincter damage.
LIFT procedure — the tract is approached through the space between the sphincter muscles. A newer technique with promising results for certain types of fistula.
Fistula plug or glue — biological materials used to fill and close the tract. Success rates vary and these are generally used in select situations.
Recovery
Recovery from fistula surgery varies by procedure but generally involves:
- Wound care — the area may need regular cleaning and dressing
- Sitz baths — warm water to keep the area clean and comfortable
- Stool management — soft stools to avoid straining
- Follow-up appointments — to monitor healing and check for recurrence
Living with a fistula
While awaiting surgery or between procedures, people describe managing with:
- Pads or dressings to manage discharge
- Regular hygiene — gentle cleaning after bowel movements
- Sitz baths for comfort
- Monitoring for signs of abscess recurrence (increasing pain, swelling, fever)
The emotional burden of living with a fistula — the discharge, the uncertainty, the impact on daily life — is significant and worth acknowledging. You are not alone in finding this condition difficult to manage.