An anal fistula is a tunnel that runs from inside the anus — the hole your body uses to get rid of solid waste -to somewhere in the skin around it. It usually follows an infection that didn’t heal the right way.
Just inside the anus are several glands that make fluid. Sometimes, they get blocked or clogged. When that happens, a bacteria build-up can create a swollen pocket of infected tissue and liquid. If it is not treated, it’ll grow. Eventually, it’ll make its way to the outside and punch a hole in the skin somewhere near the anus. The fistula is the tunnel that connects the gland to that opening.
- Inflammatory bowel disease – Crohn’s disease or ulcerative colitis
- Systemic diseases – Tuberculosis, diabetes, HIV
- History of trauma to the anal region
- Previous radiation therapy to the anal region
The most common ones are:
- Swelling around the anus.
- skin irritation around the anus
- a constant, throbbing pain that may be worse when you sit down, move around
- smelly discharge from near anus
- passing pus or blood
- swelling and redness around your anus and a high temperature (fever) if have an abscess
- difficulty controlling bowel movements (bowel incontinence) in some cases