An anal fistula is an abnormal tunnel connecting the anal canal or rectum to the skin around the anus. It commonly develops after an anal abscess and may cause persistent pain, swelling, irritation or pus discharge. While an anal fistula may not always cause severe symptoms initially, leaving it untreated can result in recurrent infections, abscess formation and other complications. This blog explains the possible complications of anal fistula and why timely surgical evaluation is important.
What Is an Anal Fistula?
An anal fistula is an abnormal passage or tunnel that develops between the inside of the anal canal and the skin near the anus. It most commonly occurs following an anal abscess, which is a collection of pus caused by an infection.
Some people with an anal fistula may notice a small opening near the anus, recurrent pus discharge, irritation or discomfort. The symptoms may come and go, leading some people to delay medical evaluation.
However, an anal fistula generally does not heal on its own and may require appropriate medical or surgical treatment.
What Happens If an Anal Fistula Is Left Untreated?
Ignoring an anal fistula can allow the underlying infection and fistulous tract to persist. In some patients, the condition can become more complex over time.
Possible complications include:
1. Persistent or Recurrent Infection
An anal fistula can provide a pathway for bacteria to travel between the anal canal and the surrounding skin. This can result in ongoing or recurrent infection.
Patients may experience:
- Persistent pus discharge
- Pain or tenderness
- Redness or irritation
- Swelling around the anus
- Repeated episodes of infection
When symptoms repeatedly return, medical evaluation is important to identify the underlying cause.
2. Recurrent Anal Abscess
An abscess is a collection of pus that develops because of an infection. If the underlying fistula remains, an abscess may develop again after it has been drained.
A recurrent abscess can cause significant pain, swelling and fever and may require urgent medical attention.
Therefore, simply treating an abscess without evaluating whether an underlying fistula is present may not always address the root problem.
3. Fistula Extension or Increasing Complexity
Over time, a fistulous tract may develop additional branches or extend through surrounding tissues.
This can make the fistula more complex and may influence the choice of treatment. The relationship of the fistula to the anal sphincter muscles is particularly important because treatment needs to control the fistula while preserving continence.
Early assessment can help the surgeon understand the anatomy of the fistula and plan appropriate treatment.
4. Fistula Recurrence
Even after treatment, anal fistulas can sometimes recur. The risk of recurrence depends on several factors, including the type and complexity of the fistula, associated disease and the treatment approach used.
Complex or branching fistulas can be more challenging to treat successfully.
Following postoperative instructions and attending scheduled follow-up appointments can help identify problems early.
5. Fecal Incontinence
Some anal fistulas involve or pass close to the anal sphincter muscles, which play an important role in controlling bowel movements.
Damage to these muscles during treatment can potentially contribute to fecal incontinence. This is why fistula treatment should be carefully planned according to the anatomy of the tract.
Modern fistula management aims to eradicate the fistula while preserving as much sphincter function as possible.
6. Severe Anorectal Infection and Sepsis
Infection associated with an anal fistula or abscess can occasionally become severe. If a serious bacterial infection spreads into the bloodstream, it can lead to sepsis, a potentially life-threatening medical emergency.
Seek urgent medical care if symptoms such as high fever, rapidly increasing pain or swelling, chills, weakness, confusion or feeling severely unwell occur.
Can an Anal Fistula Turn Into Cancer?
Cancer developing in a chronic anal fistula is rare. However, long-standing fistulas, particularly those associated with chronic inflammatory conditions, can have an increased risk of malignant transformation.
This does not mean that every untreated fistula will become cancerous. In fact, cancer is an uncommon complication.
Nevertheless, persistent or changing symptoms should be evaluated by a qualified specialist rather than ignored.
Symptoms That Should Not Be Ignored
Consider consulting a surgeon if you experience:
- Repeated pus discharge near the anus
- A small opening or wound near the anus
- Recurrent swelling
- Pain around the anus
- Repeated anal abscesses
- Skin irritation or redness
- Fever associated with anal swelling or pain
- Symptoms that repeatedly improve and return
These symptoms can have several causes, so proper diagnosis is important.
How Is Anal Fistula Diagnosed?
A surgeon generally begins with a detailed medical history and physical examination.
Depending on the location and complexity of the fistula, additional investigations such as imaging may sometimes be recommended. MRI of the pelvis can be particularly useful in selected patients with complex or recurrent fistulas.
The goal is to identify the complete fistulous tract and understand its relationship with the anal sphincter muscles before deciding on treatment.
How Is Anal Fistula Treated?
Treatment depends on the type, location and complexity of the fistula.
Depending on the individual case, treatment may include procedures such as fistulotomy, seton placement or sphincter-preserving techniques. The appropriate approach should be selected after evaluating the fistula’s anatomy and the patient’s overall condition.
The primary goals of treatment are to:
✔ Eliminate the fistulous tract
✔ Control infection
✔ Prevent recurrence
✔ Preserve anal sphincter function
There is no single procedure that is suitable for every patient. A specialist evaluation is therefore important before deciding on treatment.
Why Early Evaluation Matters
An anal fistula may appear to be a small skin problem, especially when symptoms are limited to occasional discharge. However, the underlying tract can remain active beneath the skin.
Delaying evaluation may allow recurrent infection, abscess formation or increasing fistula complexity to develop.
If you have persistent or recurrent symptoms around the anus, don’t self-treat or repeatedly ignore them. A timely surgical consultation can help determine the cause and the most appropriate treatment plan.
Takeaway
An anal fistula should not be ignored simply because the symptoms are manageable. Persistent infection, recurrent abscesses, fistula extension, recurrence and problems related to continence are among the possible complications.
Although serious complications such as sepsis and cancerous changes are uncommon, they highlight why persistent anorectal symptoms deserve proper medical evaluation.
If you experience recurrent pus discharge, swelling, pain or abscesses around the anus, consult a qualified surgeon for an appropriate evaluation.
About Dr. Nitin Jha
Dr. Nitin Jha is Director of the Department of Robotic, Laparoscopic & Minimal Access Surgery at Fortis Hospital, Noida. He provides surgical evaluation and treatment for a range of gastrointestinal, colorectal and anorectal conditions.
Don’t ignore recurring symptoms. Early evaluation can help you receive the right treatment at the right time.