Discharge or a small opening near the anus: what an anal fistula is

An anal fistula is a small tunnel running from inside the anal canal to the skin outside it. It almost always begins as an abscess. Once the tunnel has formed, antibiotics will not close it and it will not heal by itself.

Most patients arrive without the word. They describe a spot near the back passage that keeps discharging, underwear that is always marked, a lump that fills and bursts every few weeks, or a wound from a previous abscess that never quite closed. All of those describe the same thing.

Where it comes from

There are small glands inside the anal canal. If one becomes blocked and infected, it forms an abscess. The abscess finds a route to the surface, either by bursting or by being drained. When the infection settles, the route it took can stay open as a lined tunnel. That tunnel is the fistula.

This is why so many people say the same sentence: I had an abscess drained months ago and it has never been right since. That is not bad luck or bad surgery. Roughly a third of drained anal abscesses go on to leave a fistula.

Why the muscle matters more than the tunnel

The anal sphincter is what keeps you continent. Fistulas are classified by how much of that muscle the tunnel crosses, because that single fact decides which treatments are safe for you.

A superficial fistula crossing little or no muscle can be laid open, and that has the highest cure rate of anything available. A fistula crossing a significant amount of sphincter cannot be laid open without risking continence, and this is where the sphincter-preserving techniques exist.

An MRI or an endoanal ultrasound is often needed to map the tract before any decision is made. Anyone offering to treat a complex fistula without knowing its anatomy is guessing with something you cannot get back.

The options

Fistulotomy. Laying the tract open. Highest success rate, but only appropriate for low fistulas.

Seton. A fine thread left through the tract, either to drain it and settle infection before definitive treatment, or to divide the muscle very slowly over months. Effective, but living with a seton is not comfortable.

LIFT. The tract is tied off and divided in the plane between the sphincter muscles. Muscle-sparing, with reasonable published success, and it leaves a small wound between the muscles.

FiLaC, or fistula-tract laser closure. A thin laser fibre is passed along the tract and withdrawn slowly, closing the tunnel from the inside. No muscle is cut. Published series report a range of success rates, and some patients need a second session. That last sentence is not a caveat to skip over: it is the honest expectation to set before you start.

The detail on how the laser closure is done, and who it suits, is on the anal fistula treatment page.

Questions worth asking any surgeon

• How much sphincter does my tract cross, and how do you know?
• What happens to my continence with the option you are proposing?
• What is the plan if it does not close first time?
• Will I need a seton first?

What not to do

Do not keep taking repeated courses of antibiotics hoping it will close. They settle flare-ups; they do not close tunnels. And do not ignore it because it only discharges occasionally. Longstanding fistulas can become more complex over time, and complex tracts are harder to treat safely.

When to be seen urgently

Increasing pain, swelling, fever, or difficulty passing urine suggests an abscess that needs draining now.

Dr Kerim Erdem Ulucay is a DHA-licensed Specialist General and Laparoscopic Surgeon and a certified laser proctologist, consulting in Jumeirah 1 and JLT. If you have had a fistula treated before and it has returned, bring any previous operation notes or scans. Message +971 55 558 4957 or use the contact page.

General information, not a diagnosis. Treatment choice depends on examination and imaging.