Anal Fistula
A small infected tunnel between the anal canal and the skin that causes recurrent discharge and discomfort.
An anal fistula is a small abnormal tunnel that connects the inside of the anal canal to the skin near the anus. It usually follows an anal abscess and causes persistent discharge, pain and recurrent swelling. A fistula does not heal on its own — modern sphincter-sparing options such as laser (FiLaC) offer a low-pain cure.
An anal fistula often begins as a painful abscess near the anus. Even after the abscess drains, a small tunnel can remain — leaking pus or fluid and causing repeated flare-ups. Because a fistula will not close by itself, treatment is needed to cure it. Today, sphincter-sparing techniques including laser allow many patients to be treated with less pain and a lower risk to bowel control.
एनल फिस्टुला भनेको गुदाद्वार भित्रबाट छालासम्म जोडिने सानो नाली हो, जसले पिप बग्ने र पटक-पटक सुन्निने समस्या गराउँछ; यो आफैँ निको नहुने भएकाले लेजरजस्ता आधुनिक उपचार आवश्यक पर्छ।
Understanding Anal Fistula
An anal fistula is an abnormal tunnel (tract) that runs between the anal canal and the skin around the anus. Most start from tiny glands inside the anus that become blocked and infected, forming an abscess. When the abscess bursts or is drained, the tract that is left behind becomes the fistula, with an internal opening inside the anus and one or more external openings on the skin.
Fistulas vary in complexity. A simple fistula follows a short, straight path with little muscle involvement, while a complex fistula may branch, pass through more of the sphincter muscle, or have multiple openings — which affects the choice of treatment.
Symptoms
- Persistent discharge of pus, blood or foul-smelling fluid near the anus
- A small opening or lump in the skin around the anus
- Recurrent pain, swelling and redness (an abscess flaring up)
- Skin irritation, itching or soreness from constant moisture
- Pain that eases when the abscess drains, then returns
- Fever or feeling unwell during an active infection
Causes & risk factors
- A previous or recurrent anal abscess (the most common cause)
- Blocked and infected anal glands
- Inflammatory bowel disease, especially Crohn's disease
- Previous anal surgery or injury
- Tuberculosis or other chronic infections (regionally relevant)
- Radiation therapy to the pelvic area (uncommon)
Possible complications
- Recurrent abscesses and repeated painful flare-ups
- A complex fistula with multiple branching tracts
- Spread of infection to surrounding tissues
- Risk to bowel control if the sphincter muscle is damaged
- Chronic discomfort and skin breakdown from persistent discharge
How it is diagnosed
An anal fistula is diagnosed by examining the skin openings and gently assessing the tract. To map its path and its relationship to the sphincter muscles — essential for planning safe treatment — Dr. Sujan Shrestha may recommend an MRI of the pelvis or an endoanal ultrasound, particularly for complex or recurrent fistulas. This mapping helps choose a technique that cures the fistula while protecting continence.
Treatment options
An anal fistula does not heal without treatment, and the goal is to close the tunnel while preserving normal bowel control. If there is an active abscess, it is drained first. A seton (a soft thread passed through the tract) is sometimes used to control infection and allow the tissue to settle before definitive treatment. The best approach depends on how much muscle the tract involves.
Surgical treatment
Dr. Sujan Shrestha offers modern, sphincter-sparing treatments for anal fistula, including laser closure (FiLaC — Fistula-tract Laser Closure), in which a fine laser fibre gently seals the tract from within, with minimal pain and low risk to the muscle. Depending on the fistula, options such as a fistulotomy for simple tracts, LIFT, or an advancement flap may also be used. Choosing the right technique balances a lasting cure against protecting continence.
Recovery & aftercare
Recovery depends on the technique and the complexity of the fistula. After laser closure, most patients experience little pain, go home the same day, and return to routine activities within a few days. Keeping the area clean, warm sitz baths, soft stools and attending follow-up are important, as some fistulas need staged treatment. Complete healing may take a few weeks.
When to see a doctor
See a doctor if you have persistent discharge, a non-healing opening, or recurring painful swelling near the anus. Prompt attention to an anal abscess — with fever, spreading redness or severe pain — is important, as early drainage reduces the chance of a fistula forming and prevents infection from spreading.
Frequently asked questions
An established fistula almost never heals on its own because the tunnel stays open and keeps getting infected. Some form of procedure is needed to close it and stop recurrent abscesses and discharge.
FiLaC uses a fine laser fibre passed into the fistula tract to seal it gently from the inside. Because it spares the sphincter muscle and avoids a large open wound, it offers less pain and a lower risk to bowel control than some traditional operations.
Protecting continence is a central goal of treatment. Sphincter-sparing techniques such as laser and LIFT are chosen for fistulas that involve significant muscle, and careful mapping with MRI or ultrasound helps keep the sphincter safe.
Complex or branching fistulas, or underlying conditions like Crohn's disease, can make recurrence more likely. Accurate mapping, the right technique, and treating any underlying disease reduce the chance of the fistula returning.
Most fistulas begin as an anal abscess. When the abscess drains, the tract left behind can become a fistula. Early, proper drainage of an abscess lowers the risk of a fistula forming afterwards.
Get a clear answer from a specialist
Dr. Sujan Shrestha (MBBS, MS, MCh) offers evidence-based, minimally invasive care for anal fistula and the full range of GI conditions.