What Is an Anal Fistula (Fistula-in-Ano)
An anal fistula is a small channel that develops between the anal canal and the skin near the anus due to recurrent infection of a gland in the anal canal.
Visually, an anal fistula often presents as a small opening near the anus. The area might be red, swollen, and potentially discharge pus or blood. A raised area suggests an underlying abscess. The fistula itself can be a tunnel with multiple branches, not just a single visible spot. If you notice any of these signs, consulting a colorectal specialist is crucial for proper diagnosis and treatment.
Signs and Symptoms of Anal Fistula
- Recurrent infection of the anal canal
- Ongoing pain or swelling
- Drainage of pus and fluid from the abscess
What Are the Causes of Anal Fistula?
Infection of a gland in the anal canal that results in an abscess. When the abscess bursts, pus that drains from it forms a tract that eventually becomes an anal fistula after recurrent infections.
Different Types of
Anal Fistulas
Intersphincteric Anal Fistula:
An intersphincteric fistula is the most common type of anal fistula. It forms a tract between the internal sphincter and the external sphincter muscles. Typically, it starts from an infection in the anal gland and travels through the intersphincteric plane. Its external opening is usually very close to the anus.Transsphincteric Fistula:
A transsphincteric fistula goes through both the internal and external sphincter muscles, creating a more complex pathway. The tract often extends from the anal gland, passes through the sphincter muscles, and opens on the skin around the buttocks.Suprasphincteric Fistula:
In a suprasphincteric fistula, the tract begins at the anal gland, ascends above the puborectalis muscle, and then descends to open on the skin near the anus. This type of fistula bypasses the external sphincter but involves the supralevator space, making it more complex to treat.Superficial Anal Fistula:
A superficial anal fistula is the simplest type. The tract runs just beneath the skin and does not involve the sphincter muscles. As a result, it is generally easier to treat and less likely to cause significant complications. These fistulas usually result from minor infections or abscesses near the anal margin.
Risk Factors for Anal
Anal Fistulas
- Previously Drained Anal Abscess – A history of a previously drained anal abscess is a major risk factor. Abscesses that do not heal properly can lead to persistent infection, causing a fistula to form as the body attempts to drain the infection externally.
- Inflammatory Bowel Disease (IBD) – Individuals with IBD, such as Crohn's disease or ulcerative colitis, are at higher risk. These conditions cause chronic inflammation, which can lead to recurrent infections and abscesses around the anal area, eventually resulting in fistulas.
- Trauma to the Anal Area – Injuries or trauma to the anal region can damage the tissues and create pathways for infections, increasing the risk of fistula formation. This includes injuries from physical activities, accidents, or medical procedures.
- Infections of the Anal Area – Chronic or severe infections in the anal area, such as sexually transmitted infections (STIs) or frequent bacterial infections, can lead to the formation of abscesses and subsequent fistulas.
- Surgery or Radiation for Treatment of Anal Cancer – Patients who have undergone surgery or radiation therapy for anal cancer are at increased risk. Surgical procedures can inadvertently create pathways for infections, while radiation therapy can damage the surrounding tissues, leading to complications such as fistulas.
How Is an
Anal Fistula Diagnosed?
The diagnosis often begins with a detailed medical history and physical examination. The doctor will ask about symptoms, previous abscesses, and any relevant medical conditions. A physical examination of the anal area is conducted to look for external openings, discharge, or signs of infection.
For a more definitive diagnosis, additional tests may also be required. These tests include:
- MRI (Magnetic Resonance Imaging) – MRI is highly effective in diagnosing complex anal fistulas. It provides detailed images of the soft tissues, helping to identify the exact course of the fistula and any associated abscesses.
- Endoanal Ultrasound – This uses high-frequency sound waves to create images of the anal canal and surrounding structures. It can help visualise the fistula tract and its relationship with the sphincter muscles.
- Anoscope or Proctoscope – These allow direct visualisation of the anal canal and rectum. During this procedure, a doctor inserts a scope into the anus to inspect the internal opening of the fistula. This method is useful for identifying fistulas that originate inside the anal canal.
- Fistuloscopy – In this minimally invasive technique, a small scope is inserted into the fistula tract to visualise its course directly. Fistuloscopy helps map out the fistula and plan surgical treatment. It is particularly useful for complex or recurrent fistulas.
Treatment Options for
Anal Fistulas
Treating an anal fistula typically requires surgical intervention, as most fistulas do not heal on their own. Treatment depends on the type and complexity of the fistula, the patient's overall health, and the potential impact on continence.
Fistulotomy
– Fistulotomy is the most common surgical procedure for treating simple anal fistulas. This colorectal surgery involves an incision along the entire length of the fistula tract to lay it open, allowing the tissue to heal from the inside out.
Fistulotomy has a high success rate for superficial fistulas and typically results in complete healing within a few weeks. However, due to the risk of incontinence, it may not be suitable for complex fistulas involving a significant portion of the sphincter muscles.Insertion of Seton
– The insertion of a seton involves placing a surgical thread (seton) through the fistula tract to keep it open and promote drainage. This method is particularly useful for complex or high fistulas, where complete division of the sphincter muscles would cause incontinence.
Different types of setons are available, including loose setons (primarily for drainage) and cutting setons (for gradual fistulotomy). The choice depends on the specific characteristics of the fistula.Fistula Plug
– A fistula plug is a minimally invasive option that involves inserting a biodegradable plug made of collagen into the fistula tract. The plug acts as a scaffold for new tissue growth, helping the fistula to close naturally. Fistula plugs are typically used for simple or low fistulas.
While this method avoids major surgery, it has varying success rates, and some patients may require additional procedures if the fistula does not heal completely.Ligation of Intersphincteric Fistula Tract (LIFT)
– The LIFT procedure is designed to treat complex anal fistulas while preserving sphincter function. It involves tying off the fistula's internal opening within the intersphincteric plane (between the internal and external sphincter muscles).
The LIFT procedure is effective for fistulas involving a significant portion of the sphincter muscles, as it minimises the risk of incontinence. It is less invasive than traditional fistulotomy and provides a good balance between efficacy and preserving sphincter function.
Recovering From
Anal Fistula Treatment
Effective post-surgery care is crucial for a smooth recovery and preventing recurrence. Best practices include:
- Hygiene – Maintain proper hygiene to prevent infections. Warm sitz baths can help in keeping the area clean and provide pain relief.
- Diet – A high-fibre diet is recommended to ensure soft stools, which helps minimise straining during bowel movements.
- Medication – Follow the prescribed regimen, including antibiotics if provided, to prevent infection.
- Activity – Avoid heavy lifting and other strenuous activities until you have been cleared by your doctor.
Risks of
Anal Fistula Repair Surgery
Though generally a safe and effective procedure, anal fistula repair surgery can come with risks; though these are minimised when in the hands of an experienced surgeon.
- Recurring Infection – Post-surgery infections can occur, which may require additional treatment.
- Recurring Fistula – The fistula may recur even after surgery.
- Faecal Incontinence – There is a risk of faecal incontinence due to potential damage to the anal sphincter during surgery. This is one of the more serious complications and can vary in severity.
FAQs on
Anal Fistula
Can haemorrhoids lead to fistula?
Haemorrhoids do not lead to fistulas. However, complications from haemorrhoid surgery or severe inflammation may increase the risk of developing a fistula.Why do I keep getting fistulas?
Recurrent anal fistulas may happen if the initial surgery failed to fully heal the fistula tract, or if there is a persistence of underlying conditions (e.g. Crohn’s disease), or if there were surgical complications such as poor wound healing, which can increase the risk of a fistula formation.What's the difference between an anal fissure vs anal fistula?
An anal fissure is a small tear in the lining of the anus, causing sharp pain and possible bleeding during bowel movements. An anal fistula, on the other hand, is an abnormal tunnel that forms between the inside of the anus or rectum and the skin around the anus.
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