The most common cause of anal fistula is perianal abscess. Both anal fistula and perianal abscess involve infections at the anal crypts. Typically, an anal fistula forms naturally after a perianal abscess ruptures. Once an anal fistula occurs, it requires prompt surgical treatment. The primary surgical technique is fistulotomy with seton placement, thoroughly removing the local lesion and infection focus to allow fresh granulation tissue to regrow. Anal fistula is a local infectious disease of the anus, generally categorized into simple superficial anal fistula and high-risk complex anal fistula. If a high-position complex anal fistula is suspected, further diagnosis may require additional examination with pelvic MRI or perianal ultrasonography. After the rupture of a perianal abscess, it typically forms a characteristic internal and external opening, with a fistula tract connecting them, thereby forming the typical anal fistula.