Anal fistulas: Why they can be difficult to treat and what your options are
An anal fistula can be a frustrating condition. What may begin as an abscess can develop into an ongoing problem involving pain, discharge, repeated procedures and uncertainty about when, or whether, it will finally heal.
One of the most important things to understand from the outset is that anal fistulas are not always straightforward to treat. Some can be cured relatively simply, while others pass through sphincter muscles around the anus, which makes treatment much more challenging.
For complex fistulas in particular, treatment can involve several stages and often more than one procedure. Although the ultimate aim is to cure the fistula, treatment must also prioritise controlling symptoms, preventing recurrent infection and preserving continence
What is an anal fistula?
An anal fistula is an abnormal tunnel connecting the inside of the anal canal or rectum to the skin around the anus.
Most anal fistulas begin with an infection in one of the small glands inside the anus. This can develop into an abscess, which is a collection of pus near the anus. Once the abscess drains, either naturally or through surgery, a tunnel can sometimes remain between the anal canal/rectum and the skin. This tunnel is the fistula.
Other conditions can also cause fistulas, particularly Crohn’s disease, although these are managed somewhat differently from the more common (‘cryptoglandular’) fistulas that develop after an abscess.
Does receptive anal intercourse cause anal fistulas?
For people who have receptive anal intercourse, it is understandable to wonder whether sex may have caused the problem.
Receptive anal intercourse itself is not considered a cause of the usual cryptoglandular anal fistula. These fistulas generally develop because an anal gland becomes infected and forms an abscess.
Certain anal infections can contribute to abscess or fistula formation, and very rarely significant trauma can cause a different type of fistula. However, simply having receptive anal sex is not the underlying reason for fistulas to form.
What is the difference between a simple and complex anal fistula?
One of the first things a colorectal surgeon needs to understand is exactly where the fistula travels in relation to the anal sphincter muscles.
These muscles are responsible for controlling wind and bowel motions, so preserving their function is an important part of treatment.
A simple fistula generally has a relatively straightforward tract and passes through little of the external sphincter muscle.
A complex fistula may pass through a greater proportion of the sphincter, travel higher around the muscles, branch into several tracts, recur after previous treatments or occur in association with conditions such as Crohn’s disease.
This distinction matters because an effective treatment for a simple fistula may carry an unacceptable risk (especially to continence) when used for a complex one.
Why are anal fistulas so difficult to treat?
Colorectal surgeons can sometimes unintentionally downplay how challenging anal fistulas are to treat, leaving patients unsure why treatment may be prolonged or why the first procedure may not be successful. This can be particularly difficult to understand when the problem seems relatively minor or uncomplicated. Explaining this complexity from the outset can help patients set realistic expectations for treatment and recovery without constantly ‘shifting the goalposts’.
Complex anal fistulas can be difficult to cure.
The challenge is that the fistula often travels through the same muscles we are trying to protect. Completely removing or opening the tract may provide the best chance of cure, but doing so can damage the sphincter and affect bowel control.
Procedures designed to preserve the sphincter generally reduce that risk, but their healing rates tend to be lower.
This means treating a complex fistula is often a balancing act between healing the fistula and protecting continence.
It is also why treatment can sometimes take months, involve a seton for a period of time or require more than one operation. A fistula returning after treatment does not necessarily mean something has been done incorrectly. Unfortunately, recurrence is part of the reality of this disease.
Fistulas can affect more than your physical health
Living with a fistula can affect much more than bowel function.
Pain, discharge, the need to wear pads, repeated operations and uncertainty around treatment can affect confidence, relationships, mental wellbeing and sexual health.
This can be particularly significant for people who practise receptive anal intercourse.
In research I published examining the experiences of gay and bisexual men undergoing anorectal surgery, participants described significant disruption to their sexual lives and overall wellbeing. Patients with fistulas also spoke about the difficulty of not knowing how long treatment would take and how ongoing drainage affected intimacy and their confidence returning to receptive sex.
These conversations matter. Sexual wellbeing should be considered as part of fistula treatment rather than treated as something separate from it.
How are anal fistulas treated?
There is no single best treatment for every anal fistula.
The appropriate approach depends on the anatomy of the fistula, how much sphincter muscle it involves, whether there are multiple tracts or abscesses, previous treatments, continence and your individual priorities.
The main treatment options include fistulotomy or laying the fistula open, seton drainage, sphincter-preserving procedures such as LIFT or mucosal advancement flap, and newer minimally invasive treatments including Fistula Laser Closure (FiLaC).
Laying the fistula open
A fistulotomy, sometimes described as laying the fistula open, involves cutting open the fistula tract along its length, so that it can heal from the bottom upwards rather than remaining as a tunnel.
For suitable simple fistulas, this provides the highest and most reliable healing rates. A systematic review of simple fistulas reported healing in approximately 94% of patients treated with sphincter-cutting procedures, predominantly fistulotomy.
The limitation is that laying open a fistula also means dividing the sphincter muscle the fistula travels through.
For a low fistula involving very little, or no sphincter, the risks may be so low that it may be an acceptable trade-off. For a fistula passing through a substantial amount of muscle, it may create an unacceptable risk of problems controlling wind or bowel motions.
For this reason, colorectal surgeons would only recommend laying open a fistula when they believe the amount and location of sphincter involved makes it safe to do so, without affecting continence. This being said, there is always a risk that incontinence may be affected, despite our best predictions and assessment.
What is a seton?
A seton is a thin piece of soft material passed through the fistula tract and joined to form a loop. Setons are most commonly silastic bands, similar in appearance to a rubber band.
Hearing that you need a seton can understandably be confronting, but it's actually one of the most useful tools we have for managing complex fistulas.
A loose seton keeps the fistula open so that fluid and infection can drain through both openings, rather than becoming trapped and forming another abscess. It can help settle inflammation, control symptoms and give the area time to stabilise before another procedure is considered.
Importantly, a seton does not always have to be viewed as something that needs to come out as quickly as possible.
For some complex or recurrent fistulas, a comfortable loose seton can be a very effective long-term solution. European guidelines specifically recognise long-term loose setons as an option for people with complex or recurrent fistulas, particularly when further surgery may increase the risk of continence problems or when the patient simply does not want another operation.
Sometimes keeping a fistula drained, comfortable and free from repeated abscesses is a very good outcome.
A seton should not be considered a treatment failure. For the right person, it can provide stability and allow them to get back to living their life while avoiding more invasive surgery.
What is FiLaC?
FiLaC, or Fistula Laser Closure, is a minimally invasive, sphincter-preserving treatment for anal fistulas.
Rather than cutting through the anal sphincter, a fine laser fibre is passed through the fistula tract. Controlled laser energy is then delivered as the fibre is slowly withdrawn, treating the walls of the tract and encouraging it to shrink and close.
One major advantage of FiLaC is that it preserves the sphincter muscles. That means the treatment can be considered for some complex fistulas where laying the tract open would carry too great a risk to continence.
Another benefit of FiLaC is that if it does not work the first time, it can potentially be repeated. Published experience has demonstrated successful repeat treatment in selected patients. Different treatments can also be tried if FiLaC remains unsuccessful.
What are the outcomes after FiLaC?
It is important to be realistic about what is considered treatment success.
Studies of FiLaC have produced variable healing rates. A recent systematic review of more than 1,500 patients found primary healing in about 57%. Importantly, new continence problems were uncommon.
I recently co-authored a study examining FiLaC outcomes in a group of patients with anal fistulas. At first follow-up, approximately 24% had complete clinical healing, while another 40% had meaningful improvement in symptoms such as pain, bleeding or discharge. At a median follow-up of just over 10 months, 57% had either healed or experienced meaningful clinical improvement. The proportion of patients who remained without a seton increased from 32% before FiLaC to almost 68% afterwards (1).
These results are useful because they highlight that some patients have meaningful symptom improvement despite anatomical persistence of their fistula.
A fistula does not always have to disappear completely for treatment to be worthwhile
Traditionally, research tends to categorise a fistula as either healed or not healed. Real life can be more nuanced.
A patient may still technically have a small persistent tract, but no longer experience the regular discharge, pain, bleeding or recurrent abscesses that were affecting their life.
In our FiLaC study, some patients experienced significant symptomatic improvement even though their fistula had not completely healed.
That is not the same as curing a fistula, and it is important not to describe it as one.
But for someone who has spent years dealing with repeated procedures, abscesses, dressings and discomfort, an asymptomatic or minimally symptomatic fistula can still represent a meaningful win.
What happens if FiLaC does not work?
Another advantage of a sphincter-preserving approach is that it generally does not close the door on future treatment.
Depending on what happens to the tract, FiLaC may be repeated in selected patients, a seton may be replaced, or another sphincter-preserving procedure can be considered.
For some patients, surgery such as a fistulotomy may eventually become appropriate. For others, maintaining a well-drained fistula with a seton may best balance symptom control and continence preservation.
Treatment does not always follow a straight path from diagnosis, single operation and cure. Complex fistulas often require a longer-term strategy.
What should I expect if I have an anal fistula?
Perhaps the most useful thing I can tell patients with a fistula is to expect that treatment may take time, whether simple or complex.
The first priority is controlling infection and making sure any abscess is adequately drained. This may involve placing a seton, which can stabilise the fistula and treat infection, before planning the next procedure if required.
For some people, the priority is achieving the greatest possible chance of complete healing. For others, avoiding any meaningful risk to continence is more important.
There is rarely a perfect operation, but there are often several reasonable ways forward, and each option has positives and negatives. Your surgeon should help you determine what is right for you.
References
Marino MJ, Dimbleby B, Schlager L. et al. Treatment of complex perianal fistulas with fistula laser closure. Wien Klin Wochenschr. 2026
How we can help
If you have been diagnosed with an anal fistula, a colorectal surgeon can assess the fistula's anatomy and determine which treatment options are best for you.
Dr Matt Marino provides assessment and treatment for simple and complex anal fistulas, including sphincter-preserving treatment options such as FiLaC.
If you would like to arrange a consultation with Dr Marino, contact us here or call on 0493 318 188 to book an appointment.
