The seton is a surgical tool used to manage complex anal fistulas, which are abnormal tunnels connecting the anal canal to the skin near the anus. When a fistula involves a significant portion of the sphincter muscles, a simple cut (fistulotomy) risks causing permanent bowel control issues. A seton, typically a piece of surgical material, is temporarily placed through the fistula tract to manage infection. The cutting seton is a specialized technique designed for the gradual, controlled division of muscle tissue to achieve a cure while preserving anal function.
Understanding the Anal Fistula and Seton Placement
An anal fistula is an abnormal channel that forms between the anal canal lining and the perianal skin, usually resulting from a healed abscess. Surgical treatment is difficult due to the fistula’s proximity to the anal sphincter, the ring of muscles responsible for bowel continence. If the tract passes through a large segment of the sphincter, cutting it open in a single procedure can compromise muscle function and lead to incontinence.
Surgeons initially use a seton as a loose, non-cutting drain to bypass this risk. This flexible material, often a silk suture or rubber band, is looped through the fistula tract and tied loosely outside the body. This “draining seton” keeps the tract open, allowing pus and infected fluid to drain continuously, resolving inflammation and preventing abscess recurrence. This step converts a complex, infected tract into a stable channel, setting the foundation for definitive treatment.
The Mechanism of the Cutting Seton
The cutting seton differs from a draining seton by its function of gradually dividing the sphincter muscle over time. After the initial drainage phase, the seton material is progressively tightened, often every two to four weeks, to exert tension on the enclosed muscle tissue. This slow, deliberate tension causes the seton to cut through the sphincter muscle fibers.
The physiological effect of this slow division is key to preserving continence. As the seton slices through the tissue, the chronic irritation stimulates an intense inflammatory reaction, promoting the formation of dense scar tissue, or fibrosis. This fibrosis effectively binds the newly divided ends of the muscle together, preventing the sphincter from retracting and minimizing the functional gap that would occur with a single surgical cut. The gradual nature of the process allows the muscle to heal and scar as it is being divided, thereby maintaining the integrity of the anal canal’s support structure. This continues until the seton has completely migrated through the entire tract, after which it falls out on its own, leaving a healed wound.
Pre- and Post-Procedure Patient Experience
Initial seton placement is typically performed under general anesthesia, ensuring the patient is pain-free during the procedure, which takes about an hour. Pre-operative preparation often involves using an enema to cleanse the lower bowel. Patients are also instructed to temporarily stop certain medications, such as blood thinners. The surgeon identifies the entire fistula tract before placing and securing the seton.
Post-operative recovery centers on pain management and meticulous wound care, as the area remains sensitive for one to two weeks. Patients are prescribed oral analgesics to manage the pain, which can be significant due to the seton’s tension. Detailed hygiene is maintained through frequent warm sitz baths, which soothe the area, promote blood flow, and keep the surgical site clean.
Drainage is an expected part of recovery, as the seton allows continuous flow from the tract; patients are advised to use a gauze pad or sanitary napkin to manage this. Follow-up appointments are scheduled every few weeks, where the surgeon tightens the seton to advance the cutting process. Patients must maintain a high-fiber diet and adequate fluid intake to ensure soft stools, minimizing strain during bowel movements.
Long-Term Outcomes and Management
The primary goal of the cutting seton technique is to achieve a high cure rate for complex fistulas while preserving the patient’s ability to control gas and stool. Healing rates are generally high, often reported above 90%. The entire process, from initial placement to the seton falling out and final wound healing, can take several weeks to months. Complete closure typically ranges from six to twelve weeks after the final tightening.
While the technique minimizes damage, the main risk remains a change in continence, though this is often minor. Post-operative incontinence is most commonly reported as difficulty controlling flatus (gas); rates for liquid or solid stool incontinence are significantly lower. The average rate of any degree of incontinence following the cutting seton procedure is reported to be around 12%. The risk of the fistula recurring after a successful procedure is relatively low, typically falling below 10%.