Fistula in ano

Anal Fistula

Symptoms, Causes, Types, and Advanced Surgical Treatments

An anal fistula (also known as a perianal fistula) is an abnormal, infected tunnel connecting an internal gland inside the anus to the external skin surrounding the anal opening. It is a common anorectal condition that is twice as frequent in men and almost always requires medical or surgical evaluation to heal properly.

What Causes an Anal Fistula?

The vast majority (about 75%) of anal fistulas start with an infected anal gland that forms a perianal abscess—a localized collection of pus. When the abscess breaks open or is drained, an open pathway or tunnel can remain behind.

Common Risk Factors & Secondary Causes

• Previous Perianal Abscess: Nearly 50% of people who develop a perianal abscess end up with a persistent fistula.

• Inflammatory Bowel Disease (IBD): Conditions like Crohn’s disease cause chronic inflammation throughout the digestive tract, increasing fistula risk.

• Infections: Sexually transmitted infections (STIs), tuberculosis affecting the digestive tract, or rare bacterial conditions like Actinomycosis.

• Prior Trauma: Radiation therapy in the pelvic region, hidradenitis suppurativa, or previous anorectal surgeries.

Symptoms of an Anal Fistula

Anal fistula symptoms often fluctuate, worsening when the external opening closes and drainage builds up behind the skin:

• Throbbing Anal Pain: Constant or sharp discomfort that worsens when sitting, coughing, or during bowel movements.

• Persistent Drainage: Foul-smelling fluid, pus, or bloody discharge leaking from a tiny hole near the anus.

• Perianal Swelling & Redness: Inflammation and tenderness around the anal opening caused by active tissue infection (cellulitis).

• Recurrent Abscesses: Infections that seem to clear up but repeatedly return in the exact same location.

• Fever & Chills: Signs that an infection is spreading systemic signals through the body.

Classification: Types of Anal Fistulas

1. Intersphincteric

2. Transsphincteric

3. Suprasphincteric

4. Extrasphincteric

How Is an Anal Fistula Diagnosed?

A colorectal specialist diagnoses an anal fistula by evaluating your symptoms and mapping the exact course of the tunnel:

1. Clinical Physical Exam: Visual assessment of the external opening. Anoscopy or proctoscopy may be used to locate the internal opening inside the anal canal.

2. Pelvic MRI: The gold-standard non-invasive imaging test to detail the fistula tract, branching paths, and sphincter muscle involvement.

3. Endoscopic Ultrasound (EUS): An internal probe that provides high-resolution images of the surrounding muscle layers.

4. Fistulography: An X-ray utilizing contrast dye injected into the outer opening to highlight complex branching paths.

Surgical Treatment Options

Except for certain non-infected fistulas associated with Crohn’s disease (which may respond to biologic medications like infliximab), surgery is necessary to cure an anal fistula.

1. Simple Fistulas (Fistulotomy)

For straightforward fistulas involving minimal muscle (such as intersphincteric types), a fistulotomy is performed. The surgeon unroofs the tunnel, allowing it to heal flat from the inside out. This procedure has a ~95% success rate.

2. Complex Fistulas (Sphincter-Sparing Techniques)

When a fistula crosses significant sphincter muscle, aggressive cutting risks fecal incontinence. Specialized sphincter-preserving techniques are used instead:

• Seton Placement: A soft surgical thread (seton) is looped through the tract to maintain drainage, prevent new abscesses, and gradually encourage controlled healing.

• LIFT Procedure (Ligation of Intersphincteric Fistula Tract): Accesses and ties off the fistula tract between the sphincter muscles without cutting muscle tissue (~75% success rate).

• Endorectal Advancement Flap: The internal opening is covered using a flap of healthy tissue pulled down from the rectal wall.

Recovery and Long-Term Outlook

Most anal fistula repairs are outpatient procedures allowing same-day discharge. Recovery typically takes 3 to 6 weeks:

• Sitz Baths: Soaking the perianal area in warm water 2–3 times daily soothes tissue and keeps the wound clean.

• High-Fiber Diet & Hydration: Prevents constipation and straining during bowel movements.

• Wound Care: Changing sterile gauze pads regularly to absorb drainage as the channel closes.