Mucosal Advancement Flap

Overview

A mucosal advancement flap — sometimes called an endorectal advancement flap — is an operation for complex or high anal fistulas where the simpler approach of laying the fistula open (a fistulotomy) would carry too high a risk of affecting your bowel control. Instead of cutting through muscle, Mr Nguyen carefully removes the fistula tunnel, closes the internal opening (the end of the tunnel that sits inside the bowel) with stitches, and then slides a small patch of healthy bowel lining — the "flap" — down to cover and protect it. By sealing the inside end of the fistula, the tunnel loses its source and heals closed, all without touching your sphincter muscle (the muscle ring that gives you control over your bowel).

This is one of several sphincter-sparing approaches that also includes seton insertion and ligation of the intersphincteric fistula tract (LIFT — a technique that ties off the fistula tunnel between the sphincter muscles). Mr Nguyen will recommend the approach that fits your particular anatomy, the fistula's shape and location, and your sphincter function.

Who needs this procedure?

• A high transsphincteric fistula — one that passes through a significant portion of the outer sphincter muscle, making it too risky to lay open in one step
• A suprasphincteric fistula — one that goes above the sphincter muscles before tracking back down to the skin
• A fistula in someone whose sphincter muscle has already been weakened or injured — protecting the muscle you have is the priority
• A fistula that has come back after a previous fistulotomy or seton treatment
• A fistula linked to Crohn's disease in carefully selected cases where the Crohn's is well-controlled and quiet
• A rectovaginal fistula — a tunnel between the bowel and vagina near the anal junction
• Any situation where preserving your bowel control is the most important goal

Benefits

• Your sphincter muscle is completely left alone — nothing is cut, so your bowel control is not at risk from this operation
• This approach avoids the permanent incontinence risk that can come with cutting through a high fistula
• In the right candidate, one operation is all that is needed to close the fistula for good
• If the first attempt does not fully succeed, the procedure can be repeated — it does not burn any bridges for future treatment
• Nothing foreign is placed inside you — no synthetic plugs, no glue — just your own healthy tissue
• This is the natural next step if you have already had a seton in place and the inflammation has settled; the timing is carefully chosen to give the repair the best possible chance

Risks & considerations

• The fistula may not close completely: Success rates range from 50–80%, which is lower than a simple fistulotomy — but that is because this procedure is used for the harder cases where a fistulotomy is not safe. For Crohn's-related or previously-treated fistulas, success rates are at the lower end of this range. If the first attempt is not fully successful, a second repair, a LIFT procedure, or a long-term seton are all still available options.
• Flap breakdown: In a minority of cases the small patch of tissue that was moved does not fully take hold — it may retract or fail to seal perfectly. This is not a disaster; it can be re-assessed and treated again once things settle.
• Infection around the wound: There is a small chance of a new infection (perianal sepsis) developing near the repair, which may need antibiotics or a brief return to theatre for drainage. This is uncommon.
• Minor seepage in the early weeks: Some temporary leakage or mucous discharge is common in the first few weeks while the repair heals. This nearly always settles on its own as healing progresses.
• Bleeding: Uncommon, and managed by Mr Nguyen at the time of the operation.
• Persistent fistula requiring further surgery: A proportion of patients will need a repeat procedure. Mr Nguyen will discuss all remaining options with you at your follow-up — you will never be left without a plan.

Before the procedure

• An MRI of your pelvis and/or an endoanal ultrasound (an internal scan) — to map exactly where your fistula runs and check your sphincter muscle before any decision is made
• An examination under anaesthetic may have been done first to fully map the fistula and place a loose seton (drain thread), if that was appropriate for you
• Any infection must be fully settled before this repair is attempted — usually this means waiting at least 6–12 weeks after seton placement. Rushing this step reduces the chance of success, so the timing is deliberately careful
• A bowel preparation on the morning of surgery — usually a phosphate enema (a small liquid wash of the lower bowel). Mr Nguyen's rooms will explain exactly what is needed
• An antibiotic injection at the start of the anaesthetic to reduce the risk of infection
• If you take immunosuppressant medications (for Crohn's disease or other conditions), speak to your prescribing specialist about whether any adjustment is needed in the lead-up to surgery

On the day

• You will have a general anaesthetic — you will be completely asleep and feel nothing during the procedure
• Mr Nguyen gently passes a probe through the fistula tunnel to confirm its exact path, then cleans out the external opening (the end on your skin)
• He identifies the internal opening (the end inside the bowel) and carefully lifts a small flap of healthy bowel lining from just above it
• The fistula tunnel is cleaned out, and the internal opening is sewn closed in layers using dissolving stitches
• The flap of healthy tissue is then moved down — "advanced" — to cover the closed opening, giving it a strong, well-supplied seal
• The external wound (on the skin side) is left open to drain and heal naturally from the inside out — this is deliberate and important
• Most people stay overnight or for a short inpatient stay; some patients are well enough to go home the same day, depending on how the procedure went

Recovery & aftercare

• Days 0–3: Some discomfort around the area is completely normal and expected. Take your pain relief regularly — do not wait until you are sore to take it. Warm sitz baths (sitting in a shallow basin of warm water for 10–15 minutes) can start from day 1 and make a real difference to comfort and cleanliness.
• Weeks 1–2: Eat a soft, high-fibre diet and drink plenty of water to keep your bowel movements soft. Straining puts pressure on the repair, so stool softeners (which Mr Nguyen's team will recommend) are important during this period.
• 4–8 weeks: Most people have healed the external wound within this window. The flap on the inside is checked at your follow-up appointment — either by a brief in-clinic examination or a small internal look if needed.
• Avoid heavy lifting or strenuous exercise for at least 4 weeks — this gives the repair time to settle without unnecessary stress.
• Call the rooms promptly if you develop a fever, notice the pain is getting worse instead of better, or see new swelling or discharge — these are signs worth checking.
• If the fistula does come back, all is not lost — a repeat flap, a LIFT procedure, or a long-term seton are still available, and Mr Nguyen will go through the options with you at your review.
• A follow-up appointment with Mr Nguyen is routinely arranged 2–6 weeks after your procedure — the timing depends on what was done. This review is provided at no charge to you.

Related patient guides

Easy-to-read articles written for you and your family on topics related to this procedure.