Procedure
BUILD NOTE: this page was drafted for the refresh and has NOT yet been read by Dr Chen. Clinical content, and the medical-review byline above, must be confirmed by him before the domain cutover.
An anal fissure is a tear or split in the anoderm at the dentate line.1 Most heal with ointments, fibre and stool softeners, and up to half resolve with those measures alone.1 A fissure that fails to heal after four weeks is considered chronic.1 Surgery is considered when a fissure has not healed after a course of medical treatment, or when it keeps returning.
An anal fistula is an abnormal tract communicating between the perianal area and the anal canal, and occasionally the lower rectum.2 It usually begins as an abscess. About 90% of anal abscesses start with infection of the small glands inside the anus, and roughly 25% to 30% of people who have one go on to develop a fistula.2
A fistula rarely heals without surgery. The operation chosen depends on how much sphincter muscle the tunnel crosses, because protecting continence is the main constraint.
Complex fistulas sometimes need more than one operation. Dr Chen will explain the likely plan before you start.
Before the operation is chosen, the fistula is classified as simple or complex. The classification reflects how much sphincter muscle the tunnel crosses.
A simple fistula has a single short tract that crosses little sphincter muscle, with both openings close to the anus, no side branches or abscess cavity, and no other underlying condition.2 These can generally be laid open with little risk to continence.
Everything else is treated as complex, including a fistula that persists or recurs despite treatment.2 A complex fistula is not necessarily harder to cure, but it usually cannot be laid open safely. These cases require the sphincter-preserving operations, and sometimes more than one stage.
Fistulas are also classified anatomically, into intersphincteric, transsphincteric, suprasphincteric and extrasphincteric types, depending on the path the tract takes relative to the sphincter muscles.2
Most of these are day-surgery procedures under general or regional anaesthesia.
For a fistula, the tract is mapped first. The surgical plan depends on the path it takes. Endoanal ultrasound gives a full picture of the tract, and MRI is used for difficult or recurrent fistulas. Anoscopy, sigmoidoscopy, colonoscopy, fistulography and anal manometry may also be used.2
An examination under anaesthesia is sometimes arranged as a separate procedure. With the patient asleep and the sphincter relaxed, the tract can be probed and the internal opening found in a way that is not possible in clinic. The operation itself is frequently carried out in the same sitting once the anatomy is clear.
For a fissure, extensive investigation is usually unnecessary, with two exceptions. A full colonoscopy is recommended for anyone over 50 with rectal bleeding,1 and a fissure sitting away from the midline needs a biopsy to exclude Crohn’s disease, ulcerative colitis, tuberculosis, HIV and cancer.1
Most people go home the same day. Expect discomfort on opening the bowels for the first week or two, and use the pain relief and stool softeners provided. Warm baths help keep the area clean and comfortable. Some discharge from the wound is normal and can last several weeks, since these wounds heal from the base upwards rather than being closed.
BUILD NOTE: confirm typical healing times and return-to-work guidance with Dr Chen.
Wounds from fistula surgery, and from fissurectomy, are usually left open rather than stitched closed. This allows healing from the base upwards and prevents infection being trapped inside. Aftercare is more involved than for most day procedures, and discharge for several weeks is expected.
After fistula surgery the routine is a high-fibre diet with plenty of fluid, stool bulking agents and softeners, and pain relief. The area is soaked in warm water several times a day to keep it clean, and a daily wound dressing at a nearby clinic is usually needed for the first week.2
The first week involves a daily dressing appointment, a warm soak after each bowel movement, and pain relief as prescribed. From the second week onwards, dressings are usually less frequent, and care is limited to keeping the wound clean while it closes.
Do not hesitate to contact us if pain is increasing rather than settling, or if the discharge becomes thicker, heavier or offensive. Both can indicate infection or a collection that has not drained.
What you pay depends on which procedure is appropriate, whether it is done as day surgery or with an overnight stay, and on your insurance cover. MediSave can be used for approved day surgery, meaning a procedure on MOH’s Table of Surgical Procedures where you are admitted and discharged the same day.3 An Integrated Shield plan may cover part of the cost. We will give you a clear, personalised estimate, including what you can claim, before you decide.
See how our fees and claims work →
These are commonly performed procedures. As with any operation there are risks, which Dr Chen will discuss with you in the context of your own health before you begin treatment. They include bleeding, infection, delayed healing and recurrence of the fissure or fistula. Where the procedure involves the sphincter muscle, there is also a small risk of a change in control of wind or stool. The choice of procedure is made with that risk explicitly in mind.
Most fissure and fistula procedures are done as day surgery, so you go home the same day. Complex fistula surgery occasionally needs an overnight stay. Dr Chen will tell you what to expect for your procedure.
Protecting continence is the main consideration when choosing between these procedures. The fistula is mapped carefully beforehand. Procedures that divide part of the sphincter carry a small risk of affecting control of wind or stool. Alternatives that avoid cutting muscle are available. Dr Chen will discuss the specific risk in your case.
Wounds from this type of surgery are often left open to heal from the base upwards, so healing is gradual and some discharge for several weeks is normal. The timeframe varies with the procedure and the size of the wound.
Yes, recurrence is possible with any of these procedures, and the rate varies by technique and by how complex the original problem was. Keeping stools soft and regular after surgery reduces the chance of a fissure returning.
It is an assessment of the fistula with you asleep and the sphincter relaxed, which allows the tract to be probed and the internal opening found in a way that is not possible in clinic. It is often the most accurate assessment available, and the operation itself is frequently carried out in the same sitting once the anatomy is clear.
A simple fistula has a single short tract that crosses little sphincter muscle, with both openings close to the anus, no side branches or abscess cavity and no other underlying condition.2 Anything else counts as complex, including a fistula that persists or recurs despite treatment.2 Complex fistulas usually cannot be laid open safely, and the sphincter-preserving operations are used instead.
More involved than most day procedures, because the wound is left open to heal from the base upwards. The routine is a high-fibre diet with plenty of fluid, stool bulking agents and softeners, pain relief, soaking the area in warm water several times a day, and a daily wound dressing at a nearby clinic for the first week.2 Discharge for several weeks afterwards is expected.
Often. Endoanal ultrasound gives a full picture of the tract, and MRI is used for difficult or recurrent fistulas, alongside anoscopy, sigmoidoscopy, colonoscopy, fistulography and anal manometry.2 Which of these you need depends on how complex the fistula appears.
BUILD NOTE: every figure on this page carries a numbered citation. All three sources were fetched and checked on 22 September 2026. The continence figures for sphincterotomy are NUH's published rates and vary between published series; Dr Chen should confirm he is comfortable quoting them before cutover.
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