An anal fistula is a small channel that develops between the anal canal and the skin near the anus due to recurrent infection of a gland in the anal canal.
Infection of a gland in the anal canal that results in an abscess. When the abscess bursts, pus that drains from it forms a tract that eventually becomes an anal fistula after recurrent infections.
Fistulotomy: Colorectal surgery that involves making an incision in the fistula tract to open it up and then allowing the tissue to heal and merge.