Anal fistula surgery: fistulotomy, seton and other options in the UK

An anal fistula is a small tunnel that develops between the end of the bowel and the skin near the opening of the bottom. The NHS explains that it is usually caused by an infection near the anus, which results in a collection of pus (an abscess); when the pus drains away, it can leave a small channel behind. Fistulas can cause discomfort and skin irritation, smelly discharge, and pus or blood on passing stool, and they do not usually get better on their own.

This is why surgery is the standard treatment. The Northern Care Alliance leaflet says that once a fistula is established an operation is often required to manage it, and that the aim is to drain any infection while avoiding damage to the sphincter muscles, the ring of muscles that open and close the anus and are responsible for continence.

You will usually see a colorectal surgeon after a GP referral. The NHS lists a physical and rectal examination, a proctoscopy (a short telescope to look inside the anus) and an ultrasound, MRI or CT scan among the tests that may be used. The Northern Care Alliance says an MRI scan may be carried out to assess the fistula before surgery.

NHS Wales says that sometimes you may need an initial examination of the area under general anaesthetic to help determine the best treatment. The leaflet adds that some treatment decisions must be made while you are asleep during the operation, which is something to discuss with your surgeon beforehand.

The best operation depends on the position of the fistula and whether it is a single channel or branches in different directions. The NHS lists Crohn’s disease among the less common causes of fistulas, so your surgeon may ask about bowel symptoms.

The table below summarises the options described by NHS Wales, adapted from the NHS website, and the Northern Care Alliance. Your surgeon will explain which are suitable for your fistula.

A seton is a flexible thread passed along the fistula tract and tied loosely in a loop. The Northern Care Alliance explains that it allows the fistula to drain, prevents more abscesses forming and improves healing, and that you will continue to have a slight discharge. It says this is the safest option but does not cure the fistula, and that setons can stay in for weeks, months or years depending on the reason the fistula developed.

Seton care is mainly about keeping the area clean, allowing drainage and making sure the seton is not stuck. The leaflet suggests daily showers or warm salt baths, avoiding soap or perfumed products in the water until healed, regular dressing or gauze changes, and gentle daily flossing of the seton to prevent blockage. Once the initial wound has healed, it says a seton should be comfortable and should not affect bathing, swimming, sexual activity or bowel function, and that it is possible to live a full life with one.

It is understandable that learning that a seton may stay in for a long time can be stressful. The colorectal nursing team in a hospital is usually the best point of contact for advice, and your consultant’s team can explain the plan for the next stage.

NHS Wales lists the main risks as infection, which may need antibiotics and in severe cases hospital treatment; recurrence of the fistula despite surgery; and bowel incontinence, a potential risk with most types of treatment, although severe incontinence is rare and every effort is made to prevent it. The level of risk depends on the location of the fistula and the procedure.

The Northern Care Alliance explains that after a fistulotomy a small raw area heals with time, that sometimes a small dressing is needed but often the wound just needs to be kept clean with a small pad to prevent soiling, and that it is usually safe to cut a small amount of sphincter muscle, though you may notice a reduction in your ability to control wind at first, which should resolve with time.

Many people do not need to stay overnight, according to the NHS. Ask your surgical team about when you can return to work, driving and exercise, and what to do about pain, bleeding or a new abscess, because practice varies between units.

On the NHS, fistula surgery is arranged by colorectal surgeons after GP referral, often with a colorectal nurse specialist supporting seton care and dressings. Some people use private colorectal surgeons to be seen sooner, particularly for the initial assessment and scanning. Because fistula treatment may need several operations, it is sensible to ask who will be responsible for follow-up and for managing complications, and how repeat procedures would be arranged.

See a GP if you have persistent symptoms of an anal fistula, according to the NHS. After surgery, contact your surgical team or NHS 111 if you have a high temperature, worsening pain, spreading redness or swelling, or heavy bleeding. The NHS lists a high temperature with swelling and redness around the anus as a sign of an abscess, which needs prompt assessment.