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The Seton Procedure: Draining a Fistula Slowly on Purpose
By Your Health Magazine Health Information Team
You may expect surgery to close an abnormal opening immediately. So it can be confusing to learn that your surgeon wants to place a loop through an anal fistula and deliberately keep it open. That is the central idea behind a seton: controlled drainage can be safer than allowing the skin to seal while infection remains underneath.
The seton procedure for fistula surgery is often used when a fistula passes through or near the anal sphincter muscles responsible for bowel control. Instead of cutting through too much muscle at once, the surgeon places a flexible loop through the fistula tract. Depending on the type of seton and the treatment plan, it may drain the tract for weeks or months, prepare the area for another operation, or gradually treat the fistula.
Why Would a Surgeon Keep a Fistula Open?
An anal fistula is an abnormal tunnel between the anal canal and nearby skin. It commonly develops after an infected anal gland produces an abscess. Even after the abscess drains, the tunnel may remain and cause recurring swelling, pain, skin irritation, or discharge of pus, blood, or mucus.
If the outer opening closes before the tunnel is adequately treated, fluid and bacteria can become trapped. Another painful abscess may then form. A loose seton keeps the pathway open so fluid can escape instead of collecting under the skin.
This slow approach can also protect the sphincter. A straightforward fistulotomy opens the fistula along its length and can be effective for a tract involving little sphincter muscle. However, dividing a significant amount of muscle may increase the risk of difficulty controlling gas or stool. Seton drainage gives inflammation time to settle while the surgeon assesses safer options.
What Is a Seton?
A seton is a thin piece of flexible material, such as surgical thread or a soft rubber loop. The surgeon guides it through the fistula’s external opening, along the tract, and out through the internal opening in the anus. Its ends are secured together to form a loop.
There are two general approaches:
- Loose or draining seton: This seton sits loosely in the tract to maintain drainage and reduce the likelihood of another abscess. It often controls infection rather than curing the fistula by itself.
- Cutting seton: This seton is tightened in stages so it gradually moves through tissue while scarring occurs behind it. Because it may affect sphincter function and can require repeated procedures, surgeons use it selectively.
When people hear that a seton “cuts,” they may assume every seton works that way. Most discussions about placement should clarify whether the goal is drainage, staged treatment, long-term symptom control, or gradual division of the tract.
What Happens During the Procedure?
Seton placement is usually performed while the patient is under anesthesia. The surgeon examines the anal canal, identifies the fistula openings, and carefully follows the tunnel. Imaging such as an MRI may be used before surgery when the path is complex, has branches, or is difficult to define.
After the tract is located, the seton is passed through it and secured. More than one seton may be needed when multiple tracts are present. Many procedures are completed on an outpatient basis, although the plan depends on the fistula’s complexity, associated infection, underlying health conditions, and any additional surgery performed at the same time.
A seton may later be followed by fistulotomy, a LIFT procedure, an advancement flap, or another sphincter-preserving treatment. In some people, including selected patients with fistulas related to Crohn’s disease, a draining seton may remain in place for an extended period.
What Does Living With a Seton Feel Like?
Soreness, mild bleeding, and increased drainage can occur after placement. The initial discomfort commonly improves as the surgical area begins to heal, although the loop may remain noticeable. Drainage does not necessarily mean the treatment has failed; allowing drainage is one of the seton’s main purposes.
A small absorbent pad or gauze in the underwear can protect clothing. Gentle washing after bowel movements and warm baths may help keep the area clean and ease irritation. Avoid pulling, cutting, or attempting to adjust the loop unless the surgeon has specifically instructed you to do so.
Many people can walk, sit, work, exercise, and have bowel movements with a seton, but comfort varies. Cycling, prolonged sitting, heavy activity, and sexual activity may need to be limited temporarily. Follow the surgical team’s directions rather than using a fixed recovery timetable.
Constipation and straining can make recovery more uncomfortable. Patients are generally encouraged to follow their clinician’s instructions for fluids, food, bowel habits, wound care, and prescribed medicines. Individual recommendations may differ based on the operation and medical history.
How Long Does a Seton Stay In?
There is no universal removal date. A seton might remain for several weeks, several months, or longer. Timing depends on whether infection has settled, how much sphincter muscle is involved, whether the fistula is associated with Crohn’s disease, and what treatment is planned next.
A loose seton may be removed during an office visit or another procedure, but patients should never remove it themselves. Removal does not always mark the end of treatment. The surgeon may recommend another operation to close or open the remaining tract safely. For a closer look at the process, read what to expect when a seton drain is removed.
Benefits and Possible Risks
The main benefit of a draining seton is control: it provides an ongoing exit for fluid, reduces the chance of the external opening sealing too soon, and may allow inflamed tissue to settle. It can also help the surgeon avoid immediately dividing sphincter muscle.
Possible concerns include pain, bleeding, skin irritation, persistent drainage, recurrent infection, or the fistula remaining after the seton is removed. The loop can occasionally loosen, break, or move. Fistulas may also return after treatment. Changes in control of gas or stool are an important risk of fistula surgery, particularly when treatment involves sphincter muscle, but the level of risk depends on the fistula and procedure.
Patients can explore additional plain-language information through MedlinePlus health topics, while relying on their surgical team for instructions specific to their case.
When to Seek Care
Contact the treating surgeon promptly if pain or swelling is increasing rather than improving, drainage becomes foul-smelling or suddenly stops while pressure builds, or the seton falls out, breaks, or appears significantly displaced. Fever, chills, spreading redness, heavy bleeding, difficulty urinating, inability to pass stool, or feeling seriously unwell may require urgent evaluation.
Persistent anal pain, recurrent abscesses, or ongoing drainage should be assessed even if a fistula has not been diagnosed. A colorectal surgeon is the specialist who most often evaluates and treats anal fistulas. A gastroenterologist may also be involved when Crohn’s disease or another inflammatory bowel condition is suspected or already present.
The Goal Is Controlled Healing
The seton procedure for fistula surgery may seem backward because it intentionally prevents immediate closure. In reality, keeping the tract draining can reduce trapped infection and protect important muscles while the next step is planned. Understanding whether the seton is loose, cutting, temporary, or intended for longer-term drainage can make the process feel less uncertain and help patients know what to expect from recovery.
