A fistulotomy is a surgery that treats an anal fistula by cutting the tunnel open so it can heal from the inside out. It’s the most common and effective surgical option for simple anal fistulas, with recurrence rates as low as 2% to 12.5%. The procedure is typically done as an outpatient surgery, meaning you go home the same day.
What an Anal Fistula Is
An anal fistula is an abnormal tunnel that forms between the inside of your anal canal and the skin near your anus. It usually develops after an anal abscess (a pocket of infection) drains or bursts. The tunnel stays open because the infected tissue lining it doesn’t heal on its own. This leaves a passage that can leak pus, blood, or stool, causing ongoing pain and irritation. Fistulas rarely close without surgery.
How the Procedure Works
The concept behind a fistulotomy is simple: rather than trying to close the tunnel, the surgeon cuts it open and flattens it out. Think of slicing a drinking straw lengthwise and laying it flat. Once the tunnel is opened into a shallow groove, new tissue fills in from the bottom up and the wound heals naturally over several weeks.
During the surgery, you’ll receive either general anesthesia or regional anesthesia that numbs you from the waist down. The surgeon inserts a thin probe into the external opening of the fistula to trace its path and locate where it connects inside the anal canal. Once the full tract is mapped, the surgeon cuts along the entire length of the tunnel, converting it from a closed tube into an open wound. Any infected or scarred tissue lining the tract is scraped away with a small instrument called a curette, since leftover granulation tissue can delay healing. A gauze dressing is placed over the open wound to absorb fluid and blood.
Who Is a Good Candidate
Fistulotomy works best for simple fistulas, which are classified based on how much of the anal sphincter muscle (the ring of muscle that controls bowel movements) the tunnel passes through. There are two types that qualify:
- Intersphincteric fistulas travel between the two layers of sphincter muscle without crossing through the outer layer.
- Low transsphincteric fistulas pass through less than 30% of the external sphincter muscle.
For these simpler fistulas, cutting through the involved muscle tissue poses minimal risk to bowel control. Complex fistulas, which involve more sphincter muscle, are treated with sphincter-sparing techniques instead. The distinction matters because cutting through too much sphincter muscle can weaken your ability to hold in stool or gas.
Success Rates and Recurrence
Fistulotomy has one of the strongest track records of any anal fistula treatment. Recurrence rates for simple fistulotomy range from about 2% to 12.5%, depending on the study and the fistula type. That compares favorably to other options: flap procedures (where tissue is moved to cover the internal opening) have recurrence rates of 25% to 60%, and the LIFT procedure (which ties off the tract between the sphincter muscles) succeeds in about 76% of cases.
The trade-off for fistulotomy’s high success rate is the small amount of sphincter muscle that gets divided during the procedure. This is why proper patient selection is critical. When performed on the right candidates, the risk of significant bowel control problems is low.
Risk of Incontinence
The main concern with fistulotomy is the potential impact on continence. In one study of 90 patients who had the procedure, about 9% experienced some degree of incontinence afterward. Of those, the vast majority had only mild symptoms, such as occasional difficulty controlling gas. Only one patient in the study developed moderate incontinence at the 12-month follow-up.
Your individual risk depends on factors like how much sphincter muscle is involved, whether you’ve had previous anal surgeries, and your baseline sphincter function. People who already have some weakness in their sphincter, or who have had multiple fistula surgeries, face higher risk. This is one reason surgeons carefully assess the fistula’s anatomy before deciding on the approach.
Preparing for Surgery
Preparation for a fistulotomy is relatively straightforward compared to more involved bowel surgeries. You may be asked to use an enema a few hours before the procedure to clear the lower rectum. Full bowel preparation (the kind used before a colonoscopy) is generally not needed. Some hospitals allow a regular or low-residue diet the day before surgery, though you’ll need to stop eating and drinking for a set period before anesthesia, typically starting at midnight the night before.
Your surgical team may also give you medications before the procedure to help with pain control afterward. A combination of over-the-counter pain relievers and other medications given before the incision has been shown to reduce the need for stronger pain medication in the hours following anorectal surgery.
Recovery and Wound Care
You’ll stay at the hospital or surgical center until the anesthesia wears off, then go home the same day. The wound is left open intentionally so it heals from the bottom up, which means you’ll have an open area near your anus that gradually fills in with new tissue.
The most important part of recovery is keeping the wound clean. Sitz baths, where you sit in a few inches of warm water for about 20 minutes, are recommended three times a day and after every bowel movement. This helps keep the area clean, reduces discomfort, and promotes healing. You’ll wear a soft gauze pad or absorbent liner in your underwear to manage drainage, changing it frequently throughout the day.
Pain after a fistulotomy is common but manageable. Most people find it worst during bowel movements in the first week or two. Eating a high-fiber diet and staying hydrated helps keep stools soft, which makes those early bowel movements less painful. The wound typically takes several weeks to fully close, though most people can return to normal daily activities within a week or two. Complete healing time varies depending on the size and depth of the wound.
Alternatives for Complex Fistulas
When a fistula involves too much sphincter muscle for a safe fistulotomy, surgeons turn to sphincter-sparing techniques. Each has its own balance of healing rates and continence preservation.
The LIFT procedure involves tying off and dividing the fistula tract in the space between the two sphincter muscles, avoiding any muscle division. A large analysis of over 1,300 LIFT procedures found a success rate of 76%, a complication rate of 14%, and a fecal incontinence rate of just 1.4%. The American Society of Colon and Rectal Surgeons gives the LIFT procedure a strong recommendation for transsphincteric fistulas.
A cutting seton is a thread or rubber band placed through the fistula tract that slowly tightens over weeks, gradually dividing the muscle while allowing it to scar and heal behind it. Recurrence rates range from 0% to 8%, but minor incontinence is reported in 34% to 63% of patients, which is notably higher than fistulotomy for simple fistulas. Advancement flaps, where a piece of tissue is used to cover the internal opening, carry recurrence rates of 25% to 54%.
Your surgeon’s recommendation will depend on the fistula’s anatomy, your history of prior surgeries, and your current sphincter function. For straightforward fistulas that meet the criteria, fistulotomy remains the gold standard because of its combination of high success rates and a relatively quick recovery.