Will I Lose Bowel Control After Anal Fistula Surgery?

The fear of losing bowel control (fecal incontinence) is the most common concern patients have about anal fistula surgery. Fortunately, the risk of permanent, severe incontinence is very low ^[1]. Modern colorectal surgeons prioritize protecting your sphincter muscles (the rings of muscle that keep your anus closed and control your bowels) ^[2]. By using advanced imaging and specialized, muscle-sparing surgical techniques, they can effectively treat the fistula while preserving your ability to control your bowels.

Understanding the Risk: Simple vs. Complex Fistulas

The risk to your bowel control depends almost entirely on how much of the sphincter muscle the fistula tunnel passes through.

• Simple fistulas: These tunnels sit low in the anal canal and involve little to none of the sphincter muscle. For simple fistulas, surgeons typically perform a fistulotomy, which involves opening the tunnel to let it heal from the inside out. Because the muscle is mostly uninvolved, the risk of incontinence after a simple fistulotomy is very low ^[1][2].
• Complex fistulas: These tunnels pass high up, go directly through a significant portion of the sphincter muscle, or have multiple branches ^[3]. If a surgeon were to perform a standard fistulotomy on a complex fistula, the muscle would be divided, significantly increasing the risk of incontinence. To prevent this, surgeons use completely different, “sphincter-sparing” approaches ^[4].

A note on safety: If your surgeon goes into surgery expecting a simple fistula but discovers it actually involves more muscle than expected, their priority is to protect the muscle. Instead of cutting it, they will wake you up with a temporary drain (a seton) in place to keep it safe until a complex repair can be planned.

How Surgeons Protect Your Muscles

To ensure your bowel control is protected, your surgical team will likely use a combination of precise mapping, staged preparation, and muscle-sparing techniques.

Preoperative MRI Mapping

Before surgery, your doctor will likely order a pelvic MRI (Magnetic Resonance Imaging). An MRI is an essential safety tool because it provides a highly accurate “roadmap” of your anatomy ^[5][6]. It allows the surgeon to clearly see exactly how much muscle is involved and whether there are any hidden branches to the fistula ^[7][8]. This takes the guesswork out of surgery, ensuring the surgeon knows exactly which technique is safest for you.

Staged Surgery and Setons

Treating a complex fistula is often a two-step process to maximize safety and success. In the first step, your surgeon may place a seton—a small, soft surgical thread or rubber band that loops through the fistula tract ^[9]. The seton does not cut the muscle; it simply keeps the tunnel open so infection can drain out ^[10]. You will live with this seton for several weeks or months. Once the inflammation is gone and the tunnel is firm, the surgeon can safely perform a definitive sphincter-sparing surgery.

Sphincter-Sparing Surgeries

When it is time to close a complex fistula, your surgeon will avoid cutting the muscle and instead use a sphincter-sparing technique ^[11]. The most common ones include:

• The LIFT Procedure (Ligation of Intersphincteric Fistula Tract): This is one of the most effective ways to treat a complex fistula without cutting the sphincter. The surgeon accesses the fistula between the layers of muscle and ties it off. LIFT has a high success rate and carries a very low risk of fecal incontinence (around 1.4%) ^[12][1]. Compared to other complex repairs, LIFT is associated with less postoperative pain and a lower incontinence risk ^[13].
• Endorectal Advancement Flaps: In this procedure, the surgeon cleans out the fistula tunnel and covers the internal opening with a small flap of healthy tissue from inside the rectum ^[14]. While this avoids cutting the sphincter muscle, it is a delicate procedure and has a slightly higher risk of minor continence changes compared to LIFT ^[15][13]. These “minor changes” typically mean temporary difficulty holding in gas or mild seepage of mucus, rather than a total loss of solid stool control.

Other Alternatives: In some cases, surgeons may also discuss alternatives like laser closure (using targeted light to seal the tract), biologic plugs, or fibrin glue ^[16]. While these options are extremely safe for the muscle, they sometimes have lower overall success rates for permanently curing the fistula.

The Trade-Off: Incontinence vs. Recurrence

When treating complex fistulas, surgeons must balance two risks: the risk of losing bowel control and the risk of the fistula returning (recurrence) ^[2]. Sphincter-sparing surgeries are incredibly effective at protecting your muscles, but they generally have a slightly higher chance of the fistula coming back compared to more aggressive, muscle-cutting surgeries ^[17][2].

Most surgeons and patients agree that prioritizing bowel control is the right choice. If a fistula returns after a LIFT, flap, or seton procedure, it can often be operated on again safely.

A surprising benefit: For some patients, successfully treating the fistula actually improves their overall bowel control. This is because chronic inflammation, pain, and drainage from an untreated fistula can interfere with normal muscle function ^[14].