An anal fistula is an abnormal, infected tunnel connecting the anal gland (inside) to the skin surrounding the anus (outside). It is almost always the result of a previous anal abscess.
Inside the anus, there are small glands that secrete fluid. If these glands get blocked, they can become infected and develop into an abscess (a pocket of pus). As the abscess drains (or is surgically drained), it leaves a small channel—the fistula.
Fistulas rarely heal on their own and usually require surgery. Traditional surgeries (like fistulotomy) carry a risk of damaging the sphincter muscles, which can lead to incontinence.
The modern approach is Fistula-tract Laser Closure (FiLaC). A highly flexible laser probe is passed through the fistula tract. As it is slowly withdrawn, it delivers laser energy that destroys the tract wall and seals it shut from the inside. This sphincter-saving technique ensures maximum safety and rapid healing.