Anal Fistula Surgery Options: From Fistulotomy to LIFT

Anal fistula surgery encompasses a range of procedures designed to close or remove an abnormal tunnel that forms between the inside of the anal canal and the skin near the anus. The right operation depends almost entirely on how much sphincter muscle the fistula passes through, because every technique balances two competing goals: permanently healing the tract and preserving bowel control. For straightforward fistulas, a simple procedure called fistulotomy heals the problem in roughly 98 to 100 percent of cases, but complex fistulas that cross a significant portion of the sphincter demand more creative, sphincter-sparing approaches with lower but still meaningful success rates.

How Anal Fistulas Form

Most anal fistulas begin as a perianal abscess. Small glands inside the anal canal become infected, and the resulting pocket of pus either drains on its own or gets surgically drained. In a significant minority of people, the abscess leaves behind a chronic tunnel lined with tissue that refuses to close. A systematic review of the underlying process found that the initial abscess typically contains gut bacteria, yet bacteria are rarely found in the chronic fistula itself, suggesting that once the tunnel forms, inflammation rather than ongoing infection keeps it open.¹ That distinction matters for treatment: antibiotics alone almost never cure an established fistula. Surgery is the mainstay.

Why the Type of Fistula Dictates the Surgery

Surgeons classify anal fistulas based on how the tract relates to the two rings of muscle that control continence: the internal anal sphincter and the external anal sphincter. The most widely used system, Parks classification, identifies four main types. An analysis of 400 cases originally defined these categories, and the framework has been refined over the decades.² An MRI-based study of 150 primary fistulas found that about 55 percent were intersphincteric (running between the two sphincter muscles), about 39 percent were trans-sphincteric (crossing through the external sphincter), and only a small fraction were suprasphincteric or extrasphincteric, the rarest and most surgically challenging types.³

More recently, surgeons have proposed modifications that divide trans-sphincteric fistulas into “high” and “low” subtypes and group the rare suprasphincteric and extrasphincteric fistulas together, since they share similar surgical complexity.⁴ In practical terms, the distinction between “simple” and “complex” is what drives decision-making. A low intersphincteric or low trans-sphincteric fistula that involves only a small amount of muscle is simple. Anything that crosses a substantial portion of the external sphincter, has multiple branches, or occurs in the setting of Crohn’s disease is complex, and operating on it carelessly risks permanent damage to bowel control.

Imaging Before Surgery

Getting a detailed map of the fistula tract before the operation reduces surprise findings in the operating room. The two main imaging options are MRI and endoanal ultrasound. A head-to-head comparison found that endoanal ultrasound was more accurate for detecting trans-sphincteric and intersphincteric fistulas, while MRI was better at identifying suprasphincteric tracts.⁵ When it comes to detecting damage to the internal anal sphincter specifically, 3D endoanal ultrasound and external MRI show near-perfect agreement.⁶ In practice, many surgeons order MRI for complex or recurrent fistulas and reserve ultrasound for cases where MRI is unavailable or when a quick assessment in the office is sufficient.

Fistulotomy and Fistulectomy

For simple fistulas, fistulotomy remains the gold standard. The surgeon lays open the entire tract, converting the tunnel into an open groove that heals from the bottom up. The results are hard to beat. An audit of 1,250 patients at a single center reported a long-term healing rate of about 99 percent for fistulotomy in simple fistulas, with no meaningful change in continence scores when patients were selected carefully.⁷ Another audit of 675 patients found that 98 percent of fistulas healed after the first fistulotomy, and the handful that recurred were cured with a second procedure.⁸

Fistulectomy, where the entire tract is cored out rather than laid open, is a closely related procedure. A study of 90 fistulectomy patients found that about 9 percent experienced some degree of incontinence afterward, a number comparable to other techniques.⁹ The key concern with both procedures is how much sphincter they divide. One study measured the actual length of muscle cut during fistulotomy and found that a median of about 41 percent of the external sphincter and 32 percent of the internal sphincter was divided. Dividing more than two-thirds of the external sphincter was linked to higher incontinence rates, though overall continence and quality of life scores at one year did not significantly deteriorate for the group as a whole.¹⁰ This is why fistulotomy works beautifully for low, simple fistulas but becomes a gamble when the tract involves a large proportion of the sphincter.

Setons for Complex Fistulas

When a fistula is too complex for immediate fistulotomy, surgeons often place a seton, which is a thread or loop of material passed through the fistula tract and left in place. Setons serve different purposes depending on whether they are loose or tight. A loose, or draining, seton keeps the tract open so infection can drain while surrounding inflammation settles. The idea is to stage the treatment: control sepsis first, then deal with the fistula in a second operation. A study comparing seton-treated patients to other surgical approaches found that seton-treated patients had a higher rate of improvement in trans-sphincteric fistulas specifically.¹¹

A cutting seton, by contrast, is tightened over time so it slowly slices through the sphincter muscle, allowing the tissue to scar and heal behind the thread as it migrates. This preserves partial sphincter integrity compared to a single fistulotomy that divides all the muscle at once. However, a randomized trial comparing a cutting seton to a decompression-and-drainage seton found that both achieved similar wound healing rates at one year, but the drainage seton caused less postoperative pain, allowed patients to return to work faster, and resulted in better sphincter function.¹² This has nudged many surgeons away from cutting setons and toward using the loose seton primarily as a bridge to a definitive sphincter-preserving procedure.

The LIFT Procedure

Ligation of the intersphincteric fistula tract, or LIFT, is one of the most popular sphincter-preserving operations for trans-sphincteric fistulas. The surgeon accesses the fistula tract in the narrow space between the two sphincter muscles, ties it off, and divides it. Because no sphincter muscle is cut, continence is preserved. A meta-analysis pooling data from multiple studies reported a mean success rate of about 76 percent with zero incontinence.¹³ Another systematic review found a mean healing rate of about 81 percent, with all patients remaining continent after surgery and recurrence in fewer than 8 percent of cases.¹⁴

The trade-off is clear: LIFT heals fewer fistulas than fistulotomy, but it does not threaten continence. A study of 148 patients who underwent LIFT found a recurrence rate of about 23 percent, suggesting that roughly one in four or five patients will need a second procedure.¹⁵ For many patients with a complex trans-sphincteric fistula, accepting that chance of needing reoperation is preferable to risking permanent incontinence from fistulotomy.

Advancement Flaps

An endorectal or endoanal advancement flap involves cutting a flap of tissue from the rectal or anal wall, pulling it down to cover the internal opening of the fistula, and suturing it in place. The external portion of the tract is left to drain and close on its own. This technique has been used for decades and is particularly useful for high trans-sphincteric fistulas. A study of 94 patients reported a success rate of about 60 percent at a mean follow-up of roughly 40 months, with Crohn’s disease being a strong predictor of failure: patients with Crohn’s had a recurrence rate of about 57 percent compared to 33 percent in patients without it.¹⁶

A more recent study focused on long-term functional outcomes found that the overall success rate of the advancement flap was 43 percent, with the rest having an unhealed or recurrent fistula. Of concern, some patients who were fully continent before surgery reported new incontinence symptoms at long-term follow-up.¹⁷ These numbers illustrate a recurring theme in fistula surgery: techniques that spare the sphincter tend to have lower healing rates, and the healing rates look worse the longer you follow patients.

Laser Treatment

Fistula-tract laser closure, known as FiLaC, is a newer minimally invasive approach. A laser fiber is threaded through the fistula tract and fired as it is slowly withdrawn, destroying the tract lining from the inside. The appeal is minimal tissue destruction, very little postoperative pain, and preservation of the sphincter. A systematic review of studies including over 450 patients reported a primary healing rate of about 65 percent.¹⁸ A single-center study with 175 patients and a median follow-up of five years reported a similar primary healing rate of about 67 percent, with patients who had a draining seton placed before laser treatment doing significantly better than those who went straight to the laser.¹⁹ Patients who failed the first laser treatment and underwent a second round healed about 46 percent of the time, bringing the cumulative secondary success rate to nearly 74 percent.

One of the most attractive aspects of laser treatment is that patients report very low levels of postoperative pain, sometimes described as insignificant on pain scales. Even patients whose fistulas did not fully heal sometimes reported a meaningful improvement in symptoms. The procedure is still considered relatively new in the fistula surgery landscape, and the range of reported healing rates (40 to 89 percent across studies) reflects differences in patient selection and technique.²⁰

Plugs and Glue

Biological fistula plugs, made from porcine small intestinal tissue, are inserted into the tract to act as a scaffold that the body’s own tissue grows into. Fibrin glue, an injectable sealant, works on a similar idea of filling the tract without cutting muscle. Neither technique has proven especially reliable. A review of the available evidence found that success rates for the anal fistula plug ranged from about 24 to 88 percent, and fibrin glue performed even more variably, with healing rates as low as 14 percent in some studies.²¹ A head-to-head comparison found that 60 percent of fibrin glue patients still had open fistulas at three months, compared to 13 percent in the plug group.²²

Long-term plug results are less encouraging. A study with a median follow-up of eight years reported an overall healing rate of 56 percent, with plug extrusion and infection being the most common reasons for failure.²³ The plug falling out before the tract has healed around it remains the procedure’s Achilles heel. These approaches occupy a niche: they are worth trying when the fistula is relatively straightforward and the patient wants to avoid any muscle division, but expectations need to be managed.

Stem Cell Therapy for Crohn’s-Related Fistulas

Perianal fistulas associated with Crohn’s disease are a different beast. The underlying inflammatory bowel disease creates a hostile tissue environment that makes surgical healing unpredictable. Combining surgery with biologic medications like infliximab has shown better outcomes than either approach alone: a systematic review found that about 52 percent of patients achieved complete remission with combined therapy, compared to 43 percent with a single treatment approach.²⁴ Patients who received both surgery and infliximab also had shorter times to healing and longer remissions before relapse.²⁵

The most exciting development for Crohn’s fistulas is mesenchymal stem cell therapy. In a landmark phase 3 trial, injection of adipose-derived stem cells into the fistula tract achieved combined remission in half of the treated patients, compared to about a third in the placebo group.²⁶ A meta-analysis of stem cell-based therapies confirmed their effectiveness for achieving remission in treatment-resistant Crohn’s fistulas, with optimal results emerging about six months after treatment.²⁷ Across 19 studies, reported closure rates for adipose-derived stem cell therapy ranged from about 23 to 91 percent, with an average around 63 percent.²⁸

A cost analysis compared stem cell injections to fecal diversion (surgically rerouting the bowel to let the fistula heal). Allogeneic stem cells cost roughly $4,000 less per treatment episode, and autologous stem cells about $10,000 less, largely because they avoid the hospitalization and recovery associated with stoma surgery.²⁹ Stem cell treatment is currently approved in Europe (under the name darvadstrocel) but is not yet widely available everywhere, and access depends on both geography and insurance.

Living with the Aftermath

The outcomes that patients care about most, continence and long-term quality of life, are not always reported as carefully as healing rates. The reported incidence of new fecal incontinence after fistula surgery ranges widely, from about 7 to over 50 percent, depending on the fistula type, the procedure, and how incontinence is measured.³⁰ Much of that range captures mild symptoms like occasional gas leakage rather than loss of solid stool control, but the distinction matters little to the person experiencing it. A long-term follow-up study found that patients who had surgery for complex fistulas had meaningfully worse continence, more lifestyle impact, and more embarrassment than those treated for simple fistulas.³¹

Chronic pain after anal fistula surgery is an underappreciated issue. The same Thai cohort study found that about 1.6 percent of patients reported chronic postsurgical pain, and the authors noted that this outcome is rarely discussed comprehensively in the literature.³² On the positive side, patients whose recurrent fistulas were successfully treated reported significant improvements in quality of life, suggesting that dealing with a chronically draining, painful fistula is reliably worse than the aftermath of a successful operation.³³

Rectovaginal Fistulas

Fistulas that form between the rectum and the vagina represent a distinct surgical challenge. The most common cause is obstetric trauma, particularly prolonged or complicated vaginal delivery. Treatment depends on the size and location of the fistula and whether the anal sphincter is also damaged. Small, low fistulas can sometimes heal with conservative management over a period of months, but most require surgical repair.³⁴

One well-established technique for lower and mid-level rectovaginal fistulas uses a bulbocavernosus fat pad flap, sometimes called a Martius flap, to bring well-vascularized tissue into the repair. Success rates for this approach range from about 65 to 100 percent across published series.³⁵ A review of 47 patients at a teaching hospital reported a 100 percent success rate for both small fistulas repaired transvaginally and larger ones treated with a combined sphincter repair.³⁶ Complex or high rectovaginal fistulas, especially those occurring in the setting of Crohn’s disease or after pelvic radiation, may require abdominal approaches and sometimes a temporary stoma to divert stool while the repair heals.

How the Field Is Shifting

Looking at the landscape of anal fistula surgery as a whole, the clearest trend is a move away from muscle-dividing procedures and toward sphincter-preserving options, even when that means accepting lower initial healing rates. A historical perspective on the field noted that the proportion of patients undergoing traditional fistulotomy is expected to continue declining as newer techniques mature.³⁷ The logic is pragmatic: a fistula that recurs can be re-treated, but sphincter damage from an aggressive first operation can be permanent.

This shift is also driven by patient expectations. In an era when quality of life measurement is more prominent in surgical research, patients are increasingly vocal about wanting to protect continence even at the cost of additional procedures. The surgeon’s challenge is communicating realistically about the trade-offs. A straightforward low fistula should almost certainly get a fistulotomy, which heals nearly every time with minimal risk. A complex trans-sphincteric fistula deserves a staged approach: seton drainage first to clear infection, followed by a sphincter-sparing procedure like LIFT or a laser-based technique, with fistulotomy held in reserve only if the amount of sphincter at risk is genuinely small. Crohn’s patients occupy their own treatment algorithm, where the combination of biologic drugs and surgery or stem cell injections offers the most durable results. There is no single best operation for every fistula, and anyone facing this surgery benefits from a surgeon who is comfortable with the full range of techniques rather than defaulting to one approach for everyone.