Causes of Fistula

A fistula is an abnormal tunnel that connects two places that are not normally joined. This page mainly covers anal fistula (fistula-in-ano), the most common type seen in daily practice, which links the inside of the anal canal to the skin near the anus.

The usual cause: an anal abscess

Small glands just inside the anal canal can become blocked and infected, forming a pus-filled pocket (abscess). When the abscess drains, on its own or by surgery, a tunnel can remain. About a third to half of people with an anal abscess go on to develop a fistula.

Other causes

• Crohn's disease, which causes inflammation and ulcers that can tunnel through tissue
• Tuberculosis of the bowel or anus, which is more relevant in India
• Previous anal surgery, childbirth injury or trauma
• Radiation treatment to the pelvic area
• Diabetes or weak immunity, which raise the risk of infection
• Infections such as HIV-related infections and sexually transmitted infections
• Cancer, rarely

Not caused by

Spicy food, piles, or sitting on cold surfaces do not directly cause a fistula, although constipation and straining can aggravate the area.

The Ayurvedic view

Ayurveda describes this condition as bhagandara, linked to vitiated doshas and a pus-forming process near the anus. This is a traditional, interpretive framework and does not replace the modern explanation.

Why the cause matters

Finding the cause, for example Crohn's disease or tuberculosis, changes treatment, so a proper examination is important.