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Anal Fistula
An anal fistula is a small tunnel that develops between the inside of the back passage and the skin nearby, usually after an abscess. It tends to need surgery to heal.
Causes & risk factors
- A previous anal abscess that did not heal fully
- Infection of the small glands inside the anus
- Crohn’s disease
- Previous surgery or injury to the area
- Tuberculosis (less commonly)
Common symptoms
- A discharge of pus or blood near the anus
- Pain and throbbing, worse when sitting
- Skin irritation around the opening
- Fever if infected
- A small opening in the skin that keeps leaking
Tests & diagnosis
- Examination of the back passage
- MRI of the pelvis to map the tunnel
- Examination under anaesthetic
- Endoanal ultrasound
Treatment & management
- Surgery is usually needed to close the tunnel
- Laying open the tract (fistulotomy) for simple fistulas
- A seton (a soft thread) for complex fistulas
- Advanced techniques (LIFT, glue or plug) in selected cases
- Treat any underlying cause such as Crohn’s disease
When to see a doctor urgently
- Ongoing discharge, pain or swelling near the anus
- Fever with increasing pain (spreading infection)
- A recurring abscess in the same spot
- Symptoms alongside diarrhoea and weight loss
Frequently asked questions
Can an anal fistula heal without surgery?
Fistulas rarely heal on their own and usually need surgery. Treating an underlying cause, such as Crohn’s disease, is also important for healing.
What is the difference between an abscess and a fistula?
An abscess is a collection of pus that needs draining. A fistula is the tunnel that can remain afterwards, connecting the anal canal to the skin, which then needs repair.
Explore more
Sources & further reading
- World Health Organization (WHO)
- MedlinePlus — U.S. National Library of Medicine
- Ministry of Health & Family Welfare, India
- Indian Council of Medical Research (ICMR)
Reviewed by Dr. Sanjay Anbu, MBBS. MedDroid is an AI medical assistant and can make mistakes. It provides general health information, not a diagnosis or medical advice — always consult a qualified clinician. In an emergency, contact your local emergency number immediately.