Anal fistulas rarely heal naturally, and surgery is the only treatment method to achieve healing. The reasons are as follows:

Aside from an external opening on the skin around the anus, an anal fistula also has a primary infectious internal opening in the anal crypt. The two openings are interconnected, allowing bacteria and intestinal contents to enter the fistula tract through the internal opening, leading to recurrent infections. Persistent inflammation often prevents pus from draining through the external opening. There are complex relationships between the fistula and the sphincter muscles, and the frequent contraction and relaxation of the sphincter muscles can compress the tract, making it easy for pus to remain and cause infection. Therefore, surgery is necessary to completely cure an anal fistula.