Anal Fistula Causes & All Symptoms You Need To Know Anal Fistulas: Causes, Treatments, and a Breakthrough Solution for Complex Cases Evidence outside the box: Minimally invasive treatment for anal fistula Figure 1 from BIO A Fistula Plug for Treatment of Anal Fistulas Semantic Scholar Fistula in Ano An anal fistula is an abnormal tract that forms between the anal gland to the skin around the anus, often the result of a previous anal abscess that failed to heal properly.