An anal fistula is an abnormal tunnel-like connection that forms between the inside of the anal canal and the skin near the anus, usually as a result of a previous anal abscess that did not heal properly. It often develops when an infection in an anal gland drains but leaves a persistent tract that can continue to discharge pus or fluid. Symptoms commonly include pain, swelling, irritation around the anus, recurrent drainage, and sometimes fever if infection persists. Anal fistulas rarely heal on their own and typically require medical evaluation. Treatment often involves surgical procedures to remove or repair the tract while preserving anal sphincter function, along with management of any underlying infection or inflammatory bowel disease.