Is It a Fistula? Why Your Tissue May Be "Tunneling" and What to Do Next

If you've noticed a small opening near your anus, ongoing drainage, swelling, or what feels like a "tunnel" under the skin, you may be wondering: Is this a fistula?

The word fistula can sound alarming. But understanding what it is, why it happens, and what to do next can help you take calm, informed action.

Let's walk through what a fistula is, why tissue can start "tunneling," the symptoms to watch for, and your next medical steps.

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What Is a Fistula?

A fistula is an abnormal tunnel-like connection between two body parts that aren't normally connected.

In the case of an anal fistula, the tunnel forms between:

• The inside of the anal canal or rectum
• And the skin around the anus

Think of it as a small channel that develops after an infection or abscess drains or partially heals.

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Why Does Tissue Start "Tunneling"?

Tissue tunneling usually happens after an infection. Here's how it commonly develops:

1. A gland inside the anus becomes blocked
2. Bacteria grow and cause an abscess (a pocket of infection)
3. The abscess fills with pus and pressure builds
4. It either:
   • Drains on its own through the skin, or
   • Is surgically drained
5. Instead of fully healing, a small tunnel remains — this is a fistula

Up to 50% of people who develop an anal abscess may later develop an anal fistula.

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Common Symptoms of an Anal Fistula

Symptoms can vary depending on how deep or complex the fistula is. The most common signs include:

• Persistent drainage (pus or blood) from a small opening near the anus
• Recurrent swelling or pain in the same area
• Skin irritation around the anus
• Pain when sitting or during bowel movements
• A foul smell from discharge
• Fever (if infection is active)

Some fistulas drain continuously. Others close temporarily and then flare up again.

If you're unsure whether your symptoms match, you can use Ubie's free AI-powered Anal Fistula symptom checker to get personalized insights in just a few minutes.

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What Does a Fistula Feel Like?

People often describe:

• A small "pimple-like" bump that keeps coming back
• A hole or dimple in the skin
• Ongoing moisture in underwear
• A cycle of swelling → drainage → relief → swelling again

Pain is often worse during active infection and milder when draining.

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What Causes a Fistula Besides an Abscess?

While most anal fistulas result from infected anal glands, other medical conditions can increase risk:

• Crohn's disease (a type of inflammatory bowel disease)
• Previous radiation therapy
• Trauma or surgery in the area
• Tuberculosis (rare in developed countries)
• Cancer (uncommon but possible)

If you have digestive symptoms like chronic diarrhea, abdominal pain, or weight loss along with fistula symptoms, a deeper medical evaluation is important.

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Is It Always a Fistula?

Not necessarily.

Other conditions can look similar:

• Hemorrhoids
• Ingrown hairs
• Skin cysts
• Hidradenitis suppurativa
• Recurrent abscess without a fistula

This is why a proper medical exam matters. A doctor can determine whether there is an actual tunnel beneath the skin.

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How Is a Fistula Diagnosed?

A healthcare provider (often a colorectal surgeon) may:

• Perform a physical exam
• Gently probe the external opening
• Use imaging such as:
  • MRI
  • Endoanal ultrasound
  • CT scan (in complex cases)

These tests help determine:

• How deep the fistula goes
• Whether it involves sphincter muscles
• Whether it's simple or complex

This information guides treatment.

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Will a Fistula Heal on Its Own?

Most anal fistulas do not heal on their own.

Because a fistula is an abnormal tunnel lined with tissue, it usually requires medical treatment. Antibiotics alone rarely fix the problem unless there is active infection.

Leaving a fistula untreated may lead to:

• Recurrent infections
• Ongoing drainage
• Increasing pain
• Rarely, more serious complications

That said, this is typically not an emergency unless there are signs of spreading infection.

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Treatment Options for a Fistula

Treatment depends on the fistula's location and complexity. Common approaches include:

1. Fistulotomy

• The most common treatment
• The tunnel is opened surgically to allow healing from the inside out
• Often used for simple fistulas
• High success rate

2. Seton Placement

• A thin surgical thread placed in the tunnel
• Helps drain infection gradually
• Often used for complex fistulas involving muscle

3. Advanced Surgical Procedures

• LIFT procedure (ligation of intersphincteric fistula tract)
• Flap procedures
• Fibrin glue or plugs (less common)

Your surgeon will choose the safest option to preserve bowel control while eliminating the fistula.

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What Happens If You Ignore It?

While many fistulas progress slowly, ignoring symptoms can result in:

• Recurrent abscess formation
• Spreading infection
• Increased tissue damage
• Rare long-term complications

If you develop any of the following, seek medical care urgently:

• Fever over 101°F (38.3°C)
• Severe increasing pain
• Rapid swelling
• Chills
• Feeling weak or faint

These may signal a serious infection.

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When Should You See a Doctor?

You should speak to a doctor if you notice:

• Ongoing drainage near the anus
• Recurrent painful swelling
• A visible hole or opening in the skin
• Persistent discomfort lasting more than a few days
• Symptoms returning after an abscess was drained

A primary care provider can evaluate you, but many patients are referred to a colorectal specialist for confirmation and treatment planning.

Because some conditions that resemble a fistula can be more serious, it is important to speak to a doctor about any symptoms that could be life-threatening or serious.

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How to Prepare for Your Appointment

Before your visit, consider noting:

• When symptoms started
• Whether you've had an abscess before
• Any history of Crohn's disease or digestive problems
• Fever episodes
• Changes in bowel habits

Clear details help your doctor make an accurate diagnosis quickly.

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Can You Prevent a Fistula?

Not always — but you can lower risk by:

• Seeking prompt treatment for anal abscesses
• Managing inflammatory bowel disease carefully
• Practicing good hygiene
• Avoiding delaying care for rectal pain or swelling

Early treatment reduces the chance of chronic tunneling.

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The Bottom Line: Is It a Fistula?

If you're experiencing:

• Recurrent drainage
• A small opening near the anus
• Ongoing irritation or pain
• A cycle of swelling and discharge

A fistula is possible — especially if you previously had an abscess.

The good news is that anal fistulas are treatable, and many people recover fully with proper care.

If you're unsure, consider using Ubie's free AI-powered Anal Fistula symptom checker to better understand your symptoms before seeing a doctor.

Most importantly, do not ignore persistent symptoms. While fistulas are usually manageable, untreated infections can become serious. Speak to a healthcare professional promptly to protect your health and get appropriate treatment.

Taking action early is the safest and most effective step forward.