An anal fistula is usually caused by an infected anal gland that forms an abscess, which then drains and leaves a small tunnel between the anal canal and the skin. Most fistulas begin this way, but conditions like Crohn's disease, tuberculosis, trauma, and radiation can also trigger them. This article explains the main anal fistula causes, the key risk factors, warning symptoms, and how specialists diagnose and treat the condition. Understanding what causes an anal fistula helps you seek timely care and avoid complications. Read on for clear, evidence-based answers you can act on.
What Is an Anal Fistula?
An anal fistula is a small abnormal tunnel connecting the inside of the anal canal to the skin near the anus. It usually develops after an infection fails to heal properly.
These tunnels rarely close on their own and often need surgery. Understanding the structure helps explain why they form:
- Internal opening inside the anal canal
- External opening on nearby skin
- A tract lined with inflamed tissue
- Persistent drainage of pus or fluid
Learn more about anal fistula care at Lux Hospitals today.
1. Infected Anal Glands and Abscess
The most common cause is an infected anal gland. These tiny glands sit inside the anal canal and can become blocked and infected.
When infection builds up, it forms a pocket of pus called an abscess. As it drains, a fistula tunnel can remain behind.
This chain of events explains most cases:
- Anal gland becomes blocked
- Bacteria multiply inside the gland
- Pus collects and forms an abscess
- Drainage leaves a lasting tunnel
2. Untreated Perianal Abscess
A perianal abscess that is not treated promptly is a major cause of anal fistula. The trapped infection seeks a path out through the skin.
Even after drainage, around one in three abscesses leaves a fistula behind. A persistent perianal abscess should never be ignored.
Warning signs of an abscess include:
- Painful swelling near the anus
- Redness and warmth of skin
- Fever and feeling unwell
- Pus or blood discharge
Don't ignore anal swelling—consult the specialists at Lux Hospitals early.
3. Crohn's Disease and IBD
Chronic inflammation from inflammatory bowel disease can damage the bowel lining and trigger fistulas. These are often more complex and harder to heal.
Crohn's disease is especially linked to recurring anal fistulas. Managing the underlying disease is key to preventing them.
IBD-related fistulas are often marked by:
- Multiple or branching tunnels
- Frequent recurrence after treatment
- Ongoing diarrhoea and abdominal pain
- Slow wound healing
4. Infections Like Tuberculosis and HIV
Certain infections weaken tissue and promote fistula formation. Tuberculosis of the bowel is a recognised cause in many regions.
A weakened immune system, such as in HIV, also raises the risk. These fistulas may need specialised testing to identify the source.
Infections commonly involved include:
- Tuberculosis affecting the bowel
- HIV-related immune weakness
- Sexually transmitted infections
- Deep skin infections near the anus
5. Trauma, Surgery, and Radiation
Physical injury to the anal area can create a pathway for infection and fistula formation. This may follow surgery, childbirth, or an accident.
Radiation therapy for pelvic cancers can also damage tissue and lead to fistulas over time.
Common physical triggers include:
- Previous anal or rectal surgery
- Childbirth-related tears
- Radiation to the pelvic region
- Foreign-body or injury trauma
Concerned about a non-healing wound? Book an evaluation at Lux Hospitals.
Other Contributing Causes
Several less common conditions can also lead to fistulas. These often overlap with other anorectal problems.
It helps to be aware of related conditions:
- Pilonidal sinus near the tailbone
- Untreated anal fissure
- Rarely, anal or rectal cancer
- Diverticular disease complications
Common Risk Factors
Some factors make an anal fistula more likely to develop. Knowing them helps with prevention and early action.
You may be at higher risk if you have:
- Prior perianal abscess
- Chronic constipation and straining
- Diabetes or weak immunity
- Smoking and poor circulation
- Inflammatory bowel disease
Manage your risk factors—speak to the colorectal team at Lux Hospitals.
Symptoms to Watch For
Anal fistulas cause ongoing, uncomfortable symptoms that rarely resolve alone. Early recognition speeds up treatment.
Common symptoms include:
- Persistent pus or blood discharge
- Throbbing pain near the anus
- Skin irritation and itching
- Recurrent swelling or lumps
- Fever during flare-ups
How an Anal Fistula Is Diagnosed
Diagnosis starts with a physical examination of the anal area. Specialists look for the external opening and trace the tunnel.
Imaging may be needed for complex or deep fistulas. Accurate mapping guides the right surgery.
Common diagnostic steps include:
- Clinical examination of the anus
- MRI to map the tract
- Endoanal ultrasound scan
- Examination under anaesthesia
- Tests for Crohn's or TB
Get an accurate diagnosis from experienced colorectal surgeons at Lux Hospitals.
Treatment Options at Lux Hospitals
Treatment depends on the fistula's position, complexity, and cause. The goal is to heal the tunnel while protecting continence.
Lux Hospitals offers a full range of modern options:
- Filac laser fistula treatment for minimal downtime
- Fistulotomy surgery for simple tracts
- Seton placement for complex fistulas
- LIFT procedure to spare the sphincter
- VAAFT and fistula plug techniques
Why Choose Lux Hospitals?
Lux Hospitals combines advanced technology with experienced colorectal specialists. Care is tailored to each patient's cause and fistula type.
Patients benefit from a complete approach:
- Expert colorectal surgeons
- Minimally invasive laser options
- Accurate imaging and mapping
- Focus on preserving continence
- Comprehensive follow-up care
Take the first step toward healing—book your consultation at Lux Hospitals today.
Conclusion
Most anal fistulas begin with an infected anal gland or an untreated perianal abscess, but conditions like Crohn's disease, tuberculosis, trauma, and radiation can also play a role. Recognising the causes and risk factors helps you act early before complications develop.
Because fistulas rarely heal on their own, timely medical attention is essential. Specialists at Lux Hospitals offer accurate diagnosis and a full range of treatments, from laser procedures to sphincter-sparing surgery, tailored to your specific cause. If you notice persistent discharge, pain, or recurrent swelling near the anus, don't wait. Early evaluation protects your comfort, continence, and long-term health. Reach out to an experienced colorectal team for personalised care.
