What Is a Seton Placement for a Fistula?

A seton placement is a surgical procedure in which a thin loop of material is threaded through an anal fistula tract and tied loosely or snugly, keeping the channel open so it can drain and, depending on the technique, gradually heal or divide the surrounding tissue. The approach has been used for thousands of years and remains one of the most common ways surgeons manage complex fistulas that pass through the sphincter muscles controlling bowel continence. What makes setons distinctive is their flexibility: the same basic concept can be adapted to drain infection, preserve muscle function, or slowly cut through tissue, and the choice between these strategies shapes everything from recovery time to the risk of long-term complications.

How Anal Fistulas Form

An anal fistula is an abnormal tunnel that develops between the inside of the anal canal and the skin near the anus. Most arise from infection of small glands that sit at the base of the anal canal. When one of these glands becomes blocked and infected, the infection spreads outward through the tissue planes around the sphincter muscles, eventually forming an abscess. If the abscess drains (or is drained surgically) but the internal source of infection persists, the tunnel it carved on the way out remains open, creating a fistula with an internal opening inside the anal canal and one or more external openings on the skin.¹

The problem with many fistulas is their relationship to the sphincter muscles. A shallow fistula that barely grazes the muscle can be laid open surgically with little risk. But when the tract passes through a significant portion of the sphincter, simply cutting it open would damage the muscle and potentially cause incontinence. This is where setons come in: they allow the surgeon to manage the tract without making that trade-off all at once, or sometimes without making it at all.

Two Fundamental Approaches: Loose Setons and Cutting Setons

Though surgeons have come up with dozens of variations, seton placements fall into two broad categories based on what the seton is meant to do once it is in place.

A loose (or draining) seton sits in the fistula tract without any tension. Its main job is to keep the channel open so that pus and fluid drain continuously rather than building up into a new abscess. The ongoing drainage creates a controlled inflammatory response around the seton, which encourages the surrounding tissue to scar down and, in some cases, the tract to narrow or close on its own.² Many surgeons use a loose seton as a temporary measure to calm things down before a definitive repair, but it can also serve as a long-term solution when the fistula cannot safely be eliminated, particularly in patients with Crohn’s disease.

A cutting seton, by contrast, is placed with tension. The idea is that the material gradually slices through the sphincter muscle it encircles, while scar tissue forms behind it to hold the muscle together. Because the cutting happens slowly over weeks or months, the muscle is never fully divided at any single moment, which theoretically preserves continence better than a one-time surgical cut. Cutting setons have traditionally been made from materials like silk suture or rubber bands, but some surgeons fashion them from strips of latex surgical gloves, exploiting the material’s elasticity to maintain self-regulated pressure on the tissue.³

Materials Used for Setons

One of the things that surprises people about setons is how varied the materials are. There is no single “seton device” that every hospital stocks. Surgeons select materials based on whether they want a draining or cutting effect, the patient’s anatomy, and sometimes what is readily available.

Common choices include silicone vessel loops (the small, brightly colored tubes often seen in vascular surgery), Penrose drains, rubber bands, silk sutures, and even cable ties. Some surgeons combine materials: one group has described a composite seton made from two silicone vessel loops sutured together to create a thicker, more durable loop.⁴ In Crohn’s disease, where the goal is usually long-term drainage rather than cutting, surgeons may choose different seton types depending on how much discharge the tract is producing. One protocol uses thin Penrose drains for actively draining fistulas, vessel loops when pus is present but not flowing freely, and rubber bands for tracts producing only clear fluid.⁵

The material matters because it affects comfort, durability, and the degree of tissue reaction. Silicone loops are soft and well tolerated but do not cut. Rubber bands and elastic strips apply continuous pressure and are used when gradual tissue division is the goal. Silk sutures can serve as cutting setons but may fray over time.

What the Procedure Looks Like

Seton placement is typically done under regional or general anesthesia, often as a day-case procedure. The surgeon begins by identifying the internal and external openings of the fistula. A probe is passed through the tract from one opening to the other. The seton material is then attached to the probe and pulled back through the tract, forming a loop. The two ends of the loop are tied together outside the body, leaving a ring of material that runs from inside the anal canal, through the fistula, and out through the skin.

For a loose seton, the loop is tied loosely enough that it can move freely within the tract. For a cutting seton, the loop is tied more snugly so that it presses against the tissue. In either case, the external portion of the seton hangs near the anus and is visible and palpable to the patient.

When the fistula tract is long or branching, the surgery can be more involved. For tracts that extend far from the anal opening, some surgeons use a “fistula-dividing” technique: they incise the skin at the outer edge of the sphincter and place two separate setons, one encircling the sphincter muscles from the internal opening and another threading through the portion of the tract that lies outside the muscle.⁵ This breaks the problem into manageable segments.

Recovery and Follow-Up

If you have a loose seton placed, the initial recovery is relatively straightforward. Most people go home the same day. You can expect some discharge from the area, which is the point: the seton keeps the tract draining. Sitz baths, gauze pads, and mild pain relief are the typical post-operative routine. A loose seton may stay in place for weeks, months, or even indefinitely in some Crohn’s patients, and daily life generally continues around it. The seton itself does not usually cause significant pain once the initial surgical soreness subsides, though some people find it irritating or inconvenient.

Cutting setons require more active management. Because the material needs to maintain tension as it slowly divides the tissue, the surgeon periodically tightens the seton at clinic visits. One protocol calls for tightening every seven days once new tissue has grown up to the seton area, continuing until the seton cuts through and falls off.⁶ Another method uses a particular knotting technique retightened every two weeks over roughly three months.⁷ Each tightening session can cause temporary discomfort, and the overall healing time for a cutting seton is longer than for some other fistula repairs. One study comparing cutting setons to advancement flaps found the seton group took about twice as long to heal (roughly 60 days versus 30).⁸

Healing Rates and the Question of Recurrence

Most fistulas treated with setons do eventually heal, though the road can be longer than patients expect. In one series of transphincteric fistulas managed with cutting setons, about 86% had healed at a median follow-up of roughly three years, with about 12% still under active treatment.⁹ A study using loose thick setons reported complete healing rates above 90% for most patients, with some requiring a second or third procedure.¹⁰

Recurrence is the nagging problem in fistula surgery regardless of technique. When setons are compared head-to-head with alternatives like advancement flaps, the picture is mixed. Some studies find seton placement has a higher recurrence rate than flap repair, while others show no significant difference in recurrence and comparable quality-of-life outcomes.¹¹⁸ The variation reflects differences in patient populations, fistula complexity, and surgeon experience. A staged approach, where a loose seton is placed first to drain infection and an advancement flap is performed later, has shown promising results with low recurrence and minimal incontinence.¹²

Incontinence Risk

This is the question that dominates the conversation for patients facing fistula surgery: will I lose control of my bowels? The concern is legitimate, because any procedure that divides sphincter muscle carries some risk. Loose setons, by design, avoid cutting through muscle and have very low rates of incontinence. In several case series, none of the patients who received a loose seton reported significant incontinence at follow-up.¹³ One study using a combined loose-seton technique found no formed-stool incontinence, though a couple of patients experienced occasional gas or fluid leakage that improved with biofeedback therapy.¹⁴

Cutting setons pose a slightly higher theoretical risk because they do divide muscle, even if gradually. In practice, many cutting-seton series also report low incontinence rates, likely because the slow cutting allows scar tissue to take over the muscle’s function. When cutting setons are compared to the LIFT procedure (a sphincter-sparing technique), one comparison found that LIFT offered better continence preservation while the cutting seton had a lower recurrence rate, suggesting that the choice between the two depends on which risk matters more to the individual patient.¹⁵

Setons in Crohn’s Disease

Perianal fistulas are a frequent and particularly difficult problem for people with Crohn’s disease. The underlying bowel inflammation makes fistulas more likely to form, harder to heal, and more prone to recurrence. In this setting, a loose seton often becomes a cornerstone of management rather than just a bridge to definitive surgery. The seton prevents abscess formation by keeping the tract open for drainage, buying time for anti-inflammatory medications to work.

Combined treatment with seton drainage and biologic drugs (especially the anti-TNF class) has become standard practice. In a Brazilian multicenter study, patients with Crohn’s-related perianal fistulas who received both seton placement and anti-TNF therapy achieved complete perianal remission in about half of cases over a median follow-up of roughly four years, and among those who remitted, recurrence was uncommon.¹⁶ Another study found that patients responded well to seton placement combined with infliximab regardless of whether the drug was started early or late in the course of treatment.¹⁷

Quality of life is a particular concern in Crohn’s patients, who are often dealing with the burden of chronic illness on top of perianal symptoms. Research has found that Crohn’s patients with setons in place actually reported better mental health scores and disease-activity scores than those managed without setons, suggesting that the relief from persistent drainage and abscess formation outweighs the inconvenience of living with a seton.¹⁸

Imaging Before Placement

Getting the anatomy right before surgery is critical. If the surgeon misidentifies the internal opening or misses a branching tract, the seton will not drain effectively and the fistula will persist. The two main imaging tools are MRI and endoanal ultrasound.

A meta-analysis comparing the two found that three-dimensional endoanal ultrasound has high sensitivity for the most common fistula types (intersphincteric and transsphincteric), but performs less well for the rarer suprasphincteric and extrasphincteric varieties. MRI with contrast showed the highest overall accuracy across all fistula types. The current consensus is that ultrasound works well as a first-line study, with contrast-enhanced MRI reserved for complex or unclear cases.¹⁹ One head-to-head study found ultrasound accurately mapped fistula tracts about 85% of the time and was particularly good for primary fistulas, but its sensitivity dropped substantially in recurrent disease, where MRI’s ability to see the broader anatomy became more valuable.²⁰

Setons in Children

Anal fistulas in children are less common than in adults and sometimes arise from different causes, but the seton technique translates well to younger patients. A large single-institution study of 103 children treated with seton placement found that 97 experienced good healing, with an average healing time of about four weeks. Only two children with multiple fistulas experienced recurrence requiring a second procedure.²¹ An earlier study in infants specifically concluded that seton treatment was a simple and safe option for this age group.²² The fact that children generally have less complex anatomy and less chronic inflammation working against them likely contributes to these favorable results.

How Setons Compare to Newer Alternatives

Over the past couple of decades, surgeons have developed several sphincter-sparing techniques that compete with setons for complex fistulas. The LIFT procedure (which stands for ligation of the intersphincteric fistula tract) divides the tract between the sphincter muscles without cutting through the external sphincter. Advancement flaps cover the internal opening with a flap of rectal tissue. Laser ablation destroys the tract lining with thermal energy. Each has trade-offs.

When comparing LIFT to seton placement, studies have found that LIFT patients tend to have less post-operative pain and better continence preservation, but the seton group may have lower recurrence rates.²³¹⁵ Laser surgery, meanwhile, has been associated with better quality-of-life scores compared to seton fistulectomy, including less pain and better physical and psychological well-being.²⁴

None of these alternatives has made setons obsolete, however. Many of the newer procedures work best as a second step after a loose seton has already drained the infection and calmed the surrounding tissue. The seton remains the workhorse of perianal fistula management precisely because it can serve as both a treatment and a preparation for other treatments.

Experimental Directions in Seton Technology

The basic concept of threading a loop through a fistula has not changed in millennia, but researchers are now exploring whether the seton itself could be turned into a delivery vehicle for biological therapies. One approach involves coating seton materials or fistula plugs with stem cells, particularly mesenchymal stem cells derived from fat tissue. The idea is that these cells could accelerate the healing of the fistula tract from the inside. A small phase I trial tested a stem-cell-loaded fistula plug in 15 patients with transsphincteric fistulas and reported complete healing in three patients, with partial healing in seven more.²⁵ The concept of tissue-engineered setons, where the material scaffold carries cells or growth factors directly into the fistula tract, is still early-stage but represents a genuine shift in how surgeons are thinking about an ancient tool.²⁶