Anorectal abscess and fistula

An ESCP Guide for Patients

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What are anorectal abscess and fistula?

An anorectal abscess is a painful, pus-filled lump that develops near the anus. It happens when one of the small glands around the anus becomes infected. The area can become painful, swollen, red, and warm to the touch. You might also feel unwell or develop a fever. Less often, it can also be the result of the infection of an anal fissure or sexually transmitted infections. An abscess requires surgical drainage. When left untreated, the abscess can burst and drain on its own or cause a more severe infection.

An anal fistula is a small tunnel that can form between the inside of the anus and the skin around it. It often develops after an abscess has drained or healed but leaves a connection between the inside of the bowel and the outside skin. You might notice discharge, pain, or skin irritation near your bottom.

Types of anal fistula

Anal fistulas can be classified based on their location and involvement with the anal sphincter muscles. Understanding the type of fistula helps determine the best treatment approach. The main types include:

1. Extrasphincteric fistula: the least common type, originating from the rectum and bypassing the sphincter muscles entirely, often due to conditions like Crohn’s disease or trauma
2. Transsphincteric fistula: passes through both the internal and external anal sphincter muscles, often forming a horseshoe shape
3. Superficial fistula: Travels from the lower part of the anal canal to the skin, largely bypassing any sphincter muscles
4. Intersphincteric fistula: the most common type, running between the internal and external sphincter muscles without extending outward
5. Suprasphincteric fistula: begins inside the anal canal, extends above the external sphincter, and then curves down to exit near the anus

Causes and risk factors for anorectal abscess and fistula

Anorectal abscess and fistula are more common in men over 40. However, several factors can increase the risk:

• Previous history of anal abscesses.
• Inflammatory bowel disease (such as Crohn’s disease or ulcerative colitis).
• Trauma or infection in the anal area.
• Surgery or radiation treatment for anal cancer.
• Diabetes or weakened immune system.

Symptoms of anorectal abscess and fistula

You may have an anorectal abscess or fistula if you experience:

• Severe, persistent pain around the anus, worsened by sitting or passing stools
• Swelling, redness, and warmth near the anus
• Fever and general discomfort (malaise)
• Pus or foul-smelling drainage from an opening near the anus
• A visible hole or small opening in the skin near the anus

How are anorectal abscess and fistula diagnosed?

A doctor will examine the area through a clinical exam, a digital rectal exam and, if need be, an anoscopy (a small tube used to view inside the anal canal and rectum).

When doing the work-up for anal fistula, additional tests may be required, such as:

• MRI (magnetic resonance imaging)
• CT scan (computed tomography)
• Ultrasound
• Fistulography (X-ray with contrast dye)
• Examination under anesthesia

Treatment options for anorectal abscess and fistula

Surgical procedure for an abscess

The standard treatment for an abscess involves making an incision to allow pus to drain.

Small abscesses may be drained under local anesthesia, while larger abscesses often require general anesthesia to properly rinse the cavity.

Surgical procedures for anal fistula

Some of the following techniques can be combined for optimal treatment outcomes.

• Fistulotomy
  • Commonly performed for simple, low-risk fistulas
  • The fistula trajectory is laid open (cut), cleaned, and flattened to allow healing
  • Reserved for superficial fistulas, as excessive muscle division may lead to incontinence
• Fistulectomy
  • Involves the removal of the external (skin) opening and part of the fistula tunnel
  • The internal (anorectal) opening may be closed using stitches, fibrin glue, a collagen plug, or advanced surgical flaps
• Endorectal advancement flap
  • A surgical technique that uses a tissue flap from the rectal wall to cover the internal opening of the fistula
  • This procedure is recommended for complex or high-risk fistulas to reduce the risk of incontinence
  • The flap helps close the fistula while preserving sphincter muscle function
• LIFT (Ligation of intersphincteric fistula tract)
  • A surgical technique designed to treat complex fistulas while preserving sphincter function
  • The fistula tract is identified and carefully tied off (ligated) by dissecting between the internal and external sphincter muscles
  • This prevents infection from spreading while allowing the tissue to heal naturally, reducing the risk of incontinence.
• Minimally invasive techniques: Endoscopic or laser closure techniques offer promising short-term outcomes, but long-term recurrence rates remain uncertain and evidence is currently lacking to fully support these approaches.

Non-surgical treatments

• Antibiotics: these may be prescribed along with drainage to help clear the infection, especially in small abscesses
• Medications: if inflammatory bowel disease or another underlying condition is suspected, additional medications may be necessary

How to prevent recurrence

To lower the chances of developing another abscess or fistula, consider these steps:

• Manage underlying health conditions like inflammatory bowel disease
• Eat a high-fibre diet and drink plenty of fluids to prevent constipation
• Avoid straining during bowel movements
• Practice good hygiene by keeping the anal area clean and dry
• Use protection during anal sex to prevent infections

Even with treatment, recurrence is possible. Some surgical procedures carry a risk of fecal incontinence (difficulty controlling bowel movements) this is mainly due to the delicate nature of the anal canal and sphincter muscles.

When to see a doctor

See your doctor or colorectal surgeon if you notice:

• Persistent anal pain or swelling
• Fever or unusual discharge

Early diagnosis and treatment help prevent complications and support recovery.

If you have any questions, speak with your doctor or colorectal surgeon for personalised advice.

Disclaimer

The information provided here is general and hopes to correctly inform the patient to the extent possible. However, this document cannot discuss all aspects of a specific condition or procedure, or of the individual patient.

The decision on which procedure will give you the best result is made by your doctor or colorectal surgeon during consultation and based on shared and informed decision-making with the patient.