Fistula/Piles

The fistula is the tunnel that connects the gland to that opening. Most of the time, an abscess causes a fistula. It’s rare, but they can also come from conditions like tuberculosis, sexually transmitted diseases, or an ongoing illness that affects your bowels.
An anal fistula is a small tunnel that develops between the end of the bowel and the skin near the anus (where poo leaves the body). They’re usually the result of an infection near the anus causing a collection of pus (abscess) in the nearby tissue. When the pus drains away, it can leave a small channel behind.