Anal Fistula Surgery: Seton Removal & Laying Open Procedure

An anal fistula is a small tunnel running between the inside of the anal canal and the skin nearby. Most begin as an abscess: the infection drains, but the track it carved out stays open, discharging and flaring up repeatedly. Fistulas do not heal on their own, and surgery is the only reliable cure.

Every decision in fistula surgery comes down to one trade-off — curing the track versus protecting the sphincter muscle that keeps you continent. Understanding that makes the rest of this straightforward.

Why the sphincter decides everything

The fistula track usually crosses some part of the anal sphincter. Dividing muscle cures the fistula very effectively, but divide too much and continence is permanently damaged — leaking wind, soiling, or worse.

So surgeons classify fistulas by how much muscle the track involves:

• Low / simple — crosses little or no sphincter. Can usually be laid open safely.
• High / complex — crosses a significant amount of muscle, or has multiple branches, or is horseshoe-shaped, or is associated with Crohn's disease. Needs a muscle-sparing approach.

An MRI of the pelvis is often done before surgery to map the track and its relationship to the muscle. Examination under anaesthesia may be needed to complete the picture. This mapping is not a formality — it is what prevents an avoidable continence injury.

Laying open — fistulotomy

The track is opened along its length and left to heal from the base upwards. It is the oldest procedure and still the most effective, with cure rates typically above 90%, and it is the right operation for low, simple fistulas.

What to expect:

• A day-care or overnight procedure, under spinal or general anaesthesia
• An open wound left deliberately, which heals by filling in gradually over four to eight weeks
• Daily washing and dressing; sitz baths several times a day are genuinely helpful
• Discomfort for the first week or two, usually manageable with simple pain relief
• Most people return to desk work within one to two weeks

The wound looking "open" for weeks is expected — it must heal from the inside out. A wound that closes at the skin too early is how fistulas recur.

What a seton is, and why yours was placed

A seton is a thread passed through the track and tied in a loop. It is not a treatment failure or a delay tactic — it does a specific job, and there are two distinct kinds.

Draining (loose) seton

Keeps the track open so pus drains freely instead of building into another abscess. It settles inflammation, lets the track mature into a defined, fibrous tunnel, and buys time for a considered definitive operation. This is the usual first step for a complex fistula, and in Crohn's disease a draining seton is sometimes left in place long term on purpose, because it controls symptoms without risking the sphincter.

Cutting (tight) seton

Tightened progressively over weeks so it slowly divides the muscle while scar tissue forms behind it, holding the ends together. The idea is to achieve division without the muscle springing apart. It is used more selectively now, because it is uncomfortable and still carries some continence risk.

Living with a seton

• Expect ongoing discharge — that is the seton working, not a sign of infection
• A pad or gauze keeps clothing comfortable
• Sitz baths and gentle washing after opening the bowels
• Normal activity, work and exercise are generally fine

Seton removal

Timing is judged, not fixed. A draining seton usually stays in for around six to twelve weeks, until the infection has settled and the track is mature and no longer inflamed. Removal happens when your surgeon decides the next step is ready — either because the track has healed around it, or because it is time for the definitive procedure.

Removal itself is quick. A simple seton can often be taken out in the clinic in moments, with brief stinging. If a further procedure is being done at the same time, it is done under anaesthesia.

Afterwards, the small opening closes over days to weeks. Keep the area clean and dry, continue sitz baths, and expect some discharge as it settles. If it stops draining and then becomes painful and swollen, that suggests the outside has sealed while infection remains inside — get it checked.

Muscle-sparing options for complex fistulas

• LIFT — the track is tied off and divided in the space between the sphincter muscles, leaving both intact
• Advancement flap — healthy tissue is mobilised to cover the internal opening
• Laser (FiLaC) or video-assisted (VAAFT) — the track is destroyed from within, avoiding muscle division
• Fibrin glue or plug — lowest risk to continence, lowest success rates

These preserve continence better than fistulotomy but have lower cure rates, and more than one attempt is sometimes needed. That is an honest trade, not a failure — and it is why complex fistulas are treated in stages.

Risks worth discussing before you consent

• Recurrence — real for all techniques, higher for complex fistulas
• Continence change — ask specifically how much muscle your surgeon expects to divide
• Delayed healing, particularly in diabetes, smokers, or Crohn's disease
• Bleeding and infection, as with any surgery

Contact your surgeon urgently if you develop

• Fever or chills
• Increasing pain, swelling or redness rather than steady improvement
• Heavy bleeding
• Inability to pass urine
• New difficulty controlling wind or stool

If you have a fistula that has recurred, or you have been offered surgery and want the continence risk explained properly before deciding, the surgical gastroenterology team at Iswarya Hospital assesses these with imaging first and stages treatment where the track is complex.

This article provides general health information and is not a substitute for personal medical advice. Fistula anatomy varies considerably between patients — please discuss your own imaging and options with your surgeon.